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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [mm/] [filemap.c] - Rev 1765
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/* * linux/mm/filemap.c * * Copyright (C) 1994-1999 Linus Torvalds */ /* * This file handles the generic file mmap semantics used by * most "normal" filesystems (but you don't /have/ to use this: * the NFS filesystem used to do this differently, for example) */ #include <linux/module.h> #include <linux/slab.h> #include <linux/shm.h> #include <linux/mman.h> #include <linux/locks.h> #include <linux/pagemap.h> #include <linux/swap.h> #include <linux/smp_lock.h> #include <linux/blkdev.h> #include <linux/file.h> #include <linux/swapctl.h> #include <linux/init.h> #include <linux/mm.h> #include <linux/iobuf.h> #include <asm/pgalloc.h> #include <asm/uaccess.h> #include <asm/mman.h> #include <linux/highmem.h> /* * Shared mappings implemented 30.11.1994. It's not fully working yet, * though. * * Shared mappings now work. 15.8.1995 Bruno. * * finished 'unifying' the page and buffer cache and SMP-threaded the * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> * * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> */ unsigned long page_cache_size; unsigned int page_hash_bits; struct page **page_hash_table; int vm_max_readahead = 31; int vm_min_readahead = 3; EXPORT_SYMBOL(vm_max_readahead); EXPORT_SYMBOL(vm_min_readahead); spinlock_cacheline_t pagecache_lock_cacheline = {SPIN_LOCK_UNLOCKED}; /* * NOTE: to avoid deadlocking you must never acquire the pagemap_lru_lock * with the pagecache_lock held. * * Ordering: * swap_lock -> * pagemap_lru_lock -> * pagecache_lock */ spinlock_cacheline_t pagemap_lru_lock_cacheline = {SPIN_LOCK_UNLOCKED}; #define CLUSTER_PAGES (1 << page_cluster) #define CLUSTER_OFFSET(x) (((x) >> page_cluster) << page_cluster) static void FASTCALL(add_page_to_hash_queue(struct page * page, struct page **p)); static void add_page_to_hash_queue(struct page * page, struct page **p) { struct page *next = *p; *p = page; page->next_hash = next; page->pprev_hash = p; if (next) next->pprev_hash = &page->next_hash; if (page->buffers) PAGE_BUG(page); inc_nr_cache_pages(page); } static inline void add_page_to_inode_queue(struct address_space *mapping, struct page * page) { struct list_head *head = &mapping->clean_pages; mapping->nrpages++; list_add(&page->list, head); page->mapping = mapping; } static inline void remove_page_from_inode_queue(struct page * page) { struct address_space * mapping = page->mapping; if (mapping->a_ops->removepage) mapping->a_ops->removepage(page); list_del(&page->list); page->mapping = NULL; wmb(); mapping->nrpages--; if (!mapping->nrpages) refile_inode(mapping->host); } static inline void remove_page_from_hash_queue(struct page * page) { struct page *next = page->next_hash; struct page **pprev = page->pprev_hash; if (next) next->pprev_hash = pprev; *pprev = next; page->pprev_hash = NULL; dec_nr_cache_pages(page); } /* * Remove a page from the page cache and free it. Caller has to make * sure the page is locked and that nobody else uses it - or that usage * is safe. */ void __remove_inode_page(struct page *page) { remove_page_from_inode_queue(page); remove_page_from_hash_queue(page); } void remove_inode_page(struct page *page) { if (!PageLocked(page)) PAGE_BUG(page); spin_lock(&pagecache_lock); __remove_inode_page(page); spin_unlock(&pagecache_lock); } static inline int sync_page(struct page *page) { struct address_space *mapping = page->mapping; if (mapping && mapping->a_ops && mapping->a_ops->sync_page) return mapping->a_ops->sync_page(page); return 0; } /* * Add a page to the dirty page list. */ void set_page_dirty(struct page *page) { if (!test_and_set_bit(PG_dirty, &page->flags)) { struct address_space *mapping = page->mapping; if (mapping) { spin_lock(&pagecache_lock); mapping = page->mapping; if (mapping) { /* may have been truncated */ list_del(&page->list); list_add(&page->list, &mapping->dirty_pages); } spin_unlock(&pagecache_lock); if (mapping && mapping->host) mark_inode_dirty_pages(mapping->host); if (block_dump) printk(KERN_DEBUG "%s: dirtied page\n", current->comm); } } } /** * invalidate_inode_pages - Invalidate all the unlocked pages of one inode * @inode: the inode which pages we want to invalidate * * This function only removes the unlocked pages, if you want to * remove all the pages of one inode, you must call truncate_inode_pages. */ void invalidate_inode_pages(struct inode * inode) { struct list_head *head, *curr; struct page * page; head = &inode->i_mapping->clean_pages; spin_lock(&pagemap_lru_lock); spin_lock(&pagecache_lock); curr = head->next; while (curr != head) { page = list_entry(curr, struct page, list); curr = curr->next; /* We cannot invalidate something in dirty.. */ if (PageDirty(page)) continue; /* ..or locked */ if (TryLockPage(page)) continue; if (page->buffers && !try_to_free_buffers(page, 0)) goto unlock; if (page_count(page) != 1) goto unlock; __lru_cache_del(page); __remove_inode_page(page); UnlockPage(page); page_cache_release(page); continue; unlock: UnlockPage(page); continue; } spin_unlock(&pagecache_lock); spin_unlock(&pagemap_lru_lock); } static int do_flushpage(struct page *page, unsigned long offset) { int (*flushpage) (struct page *, unsigned long); flushpage = page->mapping->a_ops->flushpage; if (flushpage) return (*flushpage)(page, offset); return block_flushpage(page, offset); } static inline void truncate_partial_page(struct page *page, unsigned partial) { memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial); if (page->buffers) do_flushpage(page, partial); } static void truncate_complete_page(struct page *page) { /* Leave it on the LRU if it gets converted into anonymous buffers */ if (!page->buffers || do_flushpage(page, 0)) lru_cache_del(page); /* * We remove the page from the page cache _after_ we have * destroyed all buffer-cache references to it. Otherwise some * other process might think this inode page is not in the * page cache and creates a buffer-cache alias to it causing * all sorts of fun problems ... */ ClearPageDirty(page); ClearPageUptodate(page); remove_inode_page(page); page_cache_release(page); } static int FASTCALL(truncate_list_pages(struct list_head *, unsigned long, unsigned *)); static int truncate_list_pages(struct list_head *head, unsigned long start, unsigned *partial) { struct list_head *curr; struct page * page; int unlocked = 0; restart: curr = head->prev; while (curr != head) { unsigned long offset; page = list_entry(curr, struct page, list); offset = page->index; /* Is one of the pages to truncate? */ if ((offset >= start) || (*partial && (offset + 1) == start)) { int failed; page_cache_get(page); failed = TryLockPage(page); list_del(head); if (!failed) /* Restart after this page */ list_add_tail(head, curr); else /* Restart on this page */ list_add(head, curr); spin_unlock(&pagecache_lock); unlocked = 1; if (!failed) { if (*partial && (offset + 1) == start) { truncate_partial_page(page, *partial); *partial = 0; } else truncate_complete_page(page); UnlockPage(page); } else wait_on_page(page); page_cache_release(page); if (current->need_resched) { __set_current_state(TASK_RUNNING); schedule(); } spin_lock(&pagecache_lock); goto restart; } curr = curr->prev; } return unlocked; } /** * truncate_inode_pages - truncate *all* the pages from an offset * @mapping: mapping to truncate * @lstart: offset from with to truncate * * Truncate the page cache at a set offset, removing the pages * that are beyond that offset (and zeroing out partial pages). * If any page is locked we wait for it to become unlocked. */ void truncate_inode_pages(struct address_space * mapping, loff_t lstart) { unsigned long start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; unsigned partial = lstart & (PAGE_CACHE_SIZE - 1); int unlocked; spin_lock(&pagecache_lock); do { unlocked = truncate_list_pages(&mapping->clean_pages, start, &partial); unlocked |= truncate_list_pages(&mapping->dirty_pages, start, &partial); unlocked |= truncate_list_pages(&mapping->locked_pages, start, &partial); } while (unlocked); /* Traversed all three lists without dropping the lock */ spin_unlock(&pagecache_lock); } static inline int invalidate_this_page2(struct page * page, struct list_head * curr, struct list_head * head) { int unlocked = 1; /* * The page is locked and we hold the pagecache_lock as well * so both page_count(page) and page->buffers stays constant here. */ if (page_count(page) == 1 + !!page->buffers) { /* Restart after this page */ list_del(head); list_add_tail(head, curr); page_cache_get(page); spin_unlock(&pagecache_lock); truncate_complete_page(page); } else { if (page->buffers) { /* Restart after this page */ list_del(head); list_add_tail(head, curr); page_cache_get(page); spin_unlock(&pagecache_lock); block_invalidate_page(page); } else unlocked = 0; ClearPageDirty(page); ClearPageUptodate(page); } return unlocked; } static int FASTCALL(invalidate_list_pages2(struct list_head *)); static int invalidate_list_pages2(struct list_head *head) { struct list_head *curr; struct page * page; int unlocked = 0; restart: curr = head->prev; while (curr != head) { page = list_entry(curr, struct page, list); if (!TryLockPage(page)) { int __unlocked; __unlocked = invalidate_this_page2(page, curr, head); UnlockPage(page); unlocked |= __unlocked; if (!__unlocked) { curr = curr->prev; continue; } } else { /* Restart on this page */ list_del(head); list_add(head, curr); page_cache_get(page); spin_unlock(&pagecache_lock); unlocked = 1; wait_on_page(page); } page_cache_release(page); if (current->need_resched) { __set_current_state(TASK_RUNNING); schedule(); } spin_lock(&pagecache_lock); goto restart; } return unlocked; } /** * invalidate_inode_pages2 - Clear all the dirty bits around if it can't * free the pages because they're mapped. * @mapping: the address_space which pages we want to invalidate */ void invalidate_inode_pages2(struct address_space * mapping) { int unlocked; spin_lock(&pagecache_lock); do { unlocked = invalidate_list_pages2(&mapping->clean_pages); unlocked |= invalidate_list_pages2(&mapping->dirty_pages); unlocked |= invalidate_list_pages2(&mapping->locked_pages); } while (unlocked); spin_unlock(&pagecache_lock); } static inline struct page * __find_page_nolock(struct address_space *mapping, unsigned long offset, struct page *page) { goto inside; for (;;) { page = page->next_hash; inside: if (!page) goto not_found; if (page->mapping != mapping) continue; if (page->index == offset) break; } not_found: return page; } static int do_buffer_fdatasync(struct list_head *head, unsigned long start, unsigned long end, int (*fn)(struct page *)) { struct list_head *curr; struct page *page; int retval = 0; spin_lock(&pagecache_lock); curr = head->next; while (curr != head) { page = list_entry(curr, struct page, list); curr = curr->next; if (!page->buffers) continue; if (page->index >= end) continue; if (page->index < start) continue; page_cache_get(page); spin_unlock(&pagecache_lock); lock_page(page); /* The buffers could have been free'd while we waited for the page lock */ if (page->buffers) retval |= fn(page); UnlockPage(page); spin_lock(&pagecache_lock); curr = page->list.next; page_cache_release(page); } spin_unlock(&pagecache_lock); return retval; } /* * Two-stage data sync: first start the IO, then go back and * collect the information.. */ int generic_buffer_fdatasync(struct inode *inode, unsigned long start_idx, unsigned long end_idx) { int retval; /* writeout dirty buffers on pages from both clean and dirty lists */ retval = do_buffer_fdatasync(&inode->i_mapping->dirty_pages, start_idx, end_idx, writeout_one_page); retval |= do_buffer_fdatasync(&inode->i_mapping->clean_pages, start_idx, end_idx, writeout_one_page); retval |= do_buffer_fdatasync(&inode->i_mapping->locked_pages, start_idx, end_idx, writeout_one_page); /* now wait for locked buffers on pages from both clean and dirty lists */ retval |= do_buffer_fdatasync(&inode->i_mapping->dirty_pages, start_idx, end_idx, waitfor_one_page); retval |= do_buffer_fdatasync(&inode->i_mapping->clean_pages, start_idx, end_idx, waitfor_one_page); retval |= do_buffer_fdatasync(&inode->i_mapping->locked_pages, start_idx, end_idx, waitfor_one_page); return retval; } /* * In-memory filesystems have to fail their * writepage function - and this has to be * worked around in the VM layer.. * * We * - mark the page dirty again (but do NOT * add it back to the inode dirty list, as * that would livelock in fdatasync) * - activate the page so that the page stealer * doesn't try to write it out over and over * again. */ int fail_writepage(struct page *page) { /* Only activate on memory-pressure, not fsync.. */ if (PageLaunder(page)) { activate_page(page); SetPageReferenced(page); } /* Set the page dirty again, unlock */ SetPageDirty(page); UnlockPage(page); return 0; } EXPORT_SYMBOL(fail_writepage); /** * filemap_fdatawrite - walk the list of dirty pages of the given address space * and writepage() each unlocked page (does not wait on locked pages). * * @mapping: address space structure to write * */ int filemap_fdatawrite(struct address_space * mapping) { int ret = 0; int (*writepage)(struct page *) = mapping->a_ops->writepage; spin_lock(&pagecache_lock); while (!list_empty(&mapping->dirty_pages)) { struct page *page = list_entry(mapping->dirty_pages.prev, struct page, list); list_del(&page->list); list_add(&page->list, &mapping->locked_pages); if (!PageDirty(page)) continue; page_cache_get(page); spin_unlock(&pagecache_lock); if (!TryLockPage(page)) { if (PageDirty(page)) { int err; ClearPageDirty(page); err = writepage(page); if (err && !ret) ret = err; } else UnlockPage(page); } page_cache_release(page); spin_lock(&pagecache_lock); } spin_unlock(&pagecache_lock); return ret; } /** * filemap_fdatasync - walk the list of dirty pages of the given address space * and writepage() all of them. * * @mapping: address space structure to write * */ int filemap_fdatasync(struct address_space * mapping) { int ret = 0; int (*writepage)(struct page *) = mapping->a_ops->writepage; spin_lock(&pagecache_lock); while (!list_empty(&mapping->dirty_pages)) { struct page *page = list_entry(mapping->dirty_pages.prev, struct page, list); list_del(&page->list); list_add(&page->list, &mapping->locked_pages); if (!PageDirty(page)) continue; page_cache_get(page); spin_unlock(&pagecache_lock); lock_page(page); if (PageDirty(page)) { int err; ClearPageDirty(page); err = writepage(page); if (err && !ret) ret = err; } else UnlockPage(page); page_cache_release(page); spin_lock(&pagecache_lock); } spin_unlock(&pagecache_lock); return ret; } /** * filemap_fdatawait - walk the list of locked pages of the given address space * and wait for all of them. * * @mapping: address space structure to wait for * */ int filemap_fdatawait(struct address_space * mapping) { int ret = 0; spin_lock(&pagecache_lock); while (!list_empty(&mapping->locked_pages)) { struct page *page = list_entry(mapping->locked_pages.next, struct page, list); list_del(&page->list); list_add(&page->list, &mapping->clean_pages); if (!PageLocked(page)) continue; page_cache_get(page); spin_unlock(&pagecache_lock); ___wait_on_page(page); if (PageError(page)) ret = -EIO; page_cache_release(page); spin_lock(&pagecache_lock); } spin_unlock(&pagecache_lock); return ret; } /* * Add a page to the inode page cache. * * The caller must have locked the page and * set all the page flags correctly.. */ void add_to_page_cache_locked(struct page * page, struct address_space *mapping, unsigned long index) { if (!PageLocked(page)) BUG(); page->index = index; page_cache_get(page); spin_lock(&pagecache_lock); add_page_to_inode_queue(mapping, page); add_page_to_hash_queue(page, page_hash(mapping, index)); spin_unlock(&pagecache_lock); lru_cache_add(page); } /* * This adds a page to the page cache, starting out as locked, * owned by us, but unreferenced, not uptodate and with no errors. */ static inline void __add_to_page_cache(struct page * page, struct address_space *mapping, unsigned long offset, struct page **hash) { /* * Yes this is inefficient, however it is needed. The problem * is that we could be adding a page to the swap cache while * another CPU is also modifying page->flags, so the updates * really do need to be atomic. -- Rik */ ClearPageUptodate(page); ClearPageError(page); ClearPageDirty(page); ClearPageReferenced(page); ClearPageArch1(page); ClearPageChecked(page); LockPage(page); page_cache_get(page); page->index = offset; add_page_to_inode_queue(mapping, page); add_page_to_hash_queue(page, hash); } void add_to_page_cache(struct page * page, struct address_space * mapping, unsigned long offset) { spin_lock(&pagecache_lock); __add_to_page_cache(page, mapping, offset, page_hash(mapping, offset)); spin_unlock(&pagecache_lock); lru_cache_add(page); } int add_to_page_cache_unique(struct page * page, struct address_space *mapping, unsigned long offset, struct page **hash) { int err; struct page *alias; spin_lock(&pagecache_lock); alias = __find_page_nolock(mapping, offset, *hash); err = 1; if (!alias) { __add_to_page_cache(page,mapping,offset,hash); err = 0; } spin_unlock(&pagecache_lock); if (!err) lru_cache_add(page); return err; } /* * This adds the requested page to the page cache if it isn't already there, * and schedules an I/O to read in its contents from disk. */ static int FASTCALL(page_cache_read(struct file * file, unsigned long offset)); static int page_cache_read(struct file * file, unsigned long offset) { struct address_space *mapping = file->f_dentry->d_inode->i_mapping; struct page **hash = page_hash(mapping, offset); struct page *page; spin_lock(&pagecache_lock); page = __find_page_nolock(mapping, offset, *hash); spin_unlock(&pagecache_lock); if (page) return 0; page = page_cache_alloc(mapping); if (!page) return -ENOMEM; if (!add_to_page_cache_unique(page, mapping, offset, hash)) { int error = mapping->a_ops->readpage(file, page); page_cache_release(page); return error; } /* * We arrive here in the unlikely event that someone * raced with us and added our page to the cache first. */ page_cache_release(page); return 0; } /* * Read in an entire cluster at once. A cluster is usually a 64k- * aligned block that includes the page requested in "offset." */ static int FASTCALL(read_cluster_nonblocking(struct file * file, unsigned long offset, unsigned long filesize)); static int read_cluster_nonblocking(struct file * file, unsigned long offset, unsigned long filesize) { unsigned long pages = CLUSTER_PAGES; offset = CLUSTER_OFFSET(offset); while ((pages-- > 0) && (offset < filesize)) { int error = page_cache_read(file, offset); if (error < 0) return error; offset ++; } return 0; } /* * Knuth recommends primes in approximately golden ratio to the maximum * integer representable by a machine word for multiplicative hashing. * Chuck Lever verified the effectiveness of this technique: * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf * * These primes are chosen to be bit-sparse, that is operations on * them can use shifts and additions instead of multiplications for * machines where multiplications are slow. */ #if BITS_PER_LONG == 32 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */ #define GOLDEN_RATIO_PRIME 0x9e370001UL #elif BITS_PER_LONG == 64 /* 2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */ #define GOLDEN_RATIO_PRIME 0x9e37fffffffc0001UL #else #error Define GOLDEN_RATIO_PRIME for your wordsize. #endif /* * In order to wait for pages to become available there must be * waitqueues associated with pages. By using a hash table of * waitqueues where the bucket discipline is to maintain all * waiters on the same queue and wake all when any of the pages * become available, and for the woken contexts to check to be * sure the appropriate page became available, this saves space * at a cost of "thundering herd" phenomena during rare hash * collisions. */ static inline wait_queue_head_t *page_waitqueue(struct page *page) { const zone_t *zone = page_zone(page); wait_queue_head_t *wait = zone->wait_table; unsigned long hash = (unsigned long)page; #if BITS_PER_LONG == 64 /* Sigh, gcc can't optimise this alone like it does for 32 bits. */ unsigned long n = hash; n <<= 18; hash -= n; n <<= 33; hash -= n; n <<= 3; hash += n; n <<= 3; hash -= n; n <<= 4; hash += n; n <<= 2; hash += n; #else /* On some cpus multiply is faster, on others gcc will do shifts */ hash *= GOLDEN_RATIO_PRIME; #endif hash >>= zone->wait_table_shift; return &wait[hash]; } /* * This must be called after every submit_bh with end_io * callbacks that would result into the blkdev layer waking * up the page after a queue unplug. */ void wakeup_page_waiters(struct page * page) { wait_queue_head_t * head; head = page_waitqueue(page); if (waitqueue_active(head)) wake_up(head); } /* * Wait for a page to get unlocked. * * This must be called with the caller "holding" the page, * ie with increased "page->count" so that the page won't * go away during the wait.. * * The waiting strategy is to get on a waitqueue determined * by hashing. Waiters will then collide, and the newly woken * task must then determine whether it was woken for the page * it really wanted, and go back to sleep on the waitqueue if * that wasn't it. With the waitqueue semantics, it never leaves * the waitqueue unless it calls, so the loop moves forward one * iteration every time there is * (1) a collision * and * (2) one of the colliding pages is woken * * This is the thundering herd problem, but it is expected to * be very rare due to the few pages that are actually being * waited on at any given time and the quality of the hash function. */ void ___wait_on_page(struct page *page) { wait_queue_head_t *waitqueue = page_waitqueue(page); struct task_struct *tsk = current; DECLARE_WAITQUEUE(wait, tsk); add_wait_queue(waitqueue, &wait); do { set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (!PageLocked(page)) break; sync_page(page); schedule(); } while (PageLocked(page)); __set_task_state(tsk, TASK_RUNNING); remove_wait_queue(waitqueue, &wait); } /* * unlock_page() is the other half of the story just above * __wait_on_page(). Here a couple of quick checks are done * and a couple of flags are set on the page, and then all * of the waiters for all of the pages in the appropriate * wait queue are woken. */ void unlock_page(struct page *page) { wait_queue_head_t *waitqueue = page_waitqueue(page); ClearPageLaunder(page); smp_mb__before_clear_bit(); if (!test_and_clear_bit(PG_locked, &(page)->flags)) BUG(); smp_mb__after_clear_bit(); /* * Although the default semantics of wake_up() are * to wake all, here the specific function is used * to make it even more explicit that a number of * pages are being waited on here. */ if (waitqueue_active(waitqueue)) wake_up_all(waitqueue); } /* * Get a lock on the page, assuming we need to sleep * to get it.. */ static void __lock_page(struct page *page) { wait_queue_head_t *waitqueue = page_waitqueue(page); struct task_struct *tsk = current; DECLARE_WAITQUEUE(wait, tsk); add_wait_queue_exclusive(waitqueue, &wait); for (;;) { set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (PageLocked(page)) { sync_page(page); schedule(); } if (!TryLockPage(page)) break; } __set_task_state(tsk, TASK_RUNNING); remove_wait_queue(waitqueue, &wait); } /* * Get an exclusive lock on the page, optimistically * assuming it's not locked.. */ void lock_page(struct page *page) { if (TryLockPage(page)) __lock_page(page); } /* * a rather lightweight function, finding and getting a reference to a * hashed page atomically. */ struct page * __find_get_page(struct address_space *mapping, unsigned long offset, struct page **hash) { struct page *page; /* * We scan the hash list read-only. Addition to and removal from * the hash-list needs a held write-lock. */ spin_lock(&pagecache_lock); page = __find_page_nolock(mapping, offset, *hash); if (page) page_cache_get(page); spin_unlock(&pagecache_lock); return page; } /* * Same as above, but trylock it instead of incrementing the count. */ struct page *find_trylock_page(struct address_space *mapping, unsigned long offset) { struct page *page; struct page **hash = page_hash(mapping, offset); spin_lock(&pagecache_lock); page = __find_page_nolock(mapping, offset, *hash); if (page) { if (TryLockPage(page)) page = NULL; } spin_unlock(&pagecache_lock); return page; } /* * Must be called with the pagecache lock held, * will return with it held (but it may be dropped * during blocking operations.. */ static struct page * FASTCALL(__find_lock_page_helper(struct address_space *, unsigned long, struct page *)); static struct page * __find_lock_page_helper(struct address_space *mapping, unsigned long offset, struct page *hash) { struct page *page; /* * We scan the hash list read-only. Addition to and removal from * the hash-list needs a held write-lock. */ repeat: page = __find_page_nolock(mapping, offset, hash); if (page) { page_cache_get(page); if (TryLockPage(page)) { spin_unlock(&pagecache_lock); lock_page(page); spin_lock(&pagecache_lock); /* Has the page been re-allocated while we slept? */ if (page->mapping != mapping || page->index != offset) { UnlockPage(page); page_cache_release(page); goto repeat; } } } return page; } /* * Same as the above, but lock the page too, verifying that * it's still valid once we own it. */ struct page * __find_lock_page (struct address_space *mapping, unsigned long offset, struct page **hash) { struct page *page; spin_lock(&pagecache_lock); page = __find_lock_page_helper(mapping, offset, *hash); spin_unlock(&pagecache_lock); return page; } /* * Same as above, but create the page if required.. */ struct page * find_or_create_page(struct address_space *mapping, unsigned long index, unsigned int gfp_mask) { struct page *page; struct page **hash = page_hash(mapping, index); spin_lock(&pagecache_lock); page = __find_lock_page_helper(mapping, index, *hash); spin_unlock(&pagecache_lock); if (!page) { struct page *newpage = alloc_page(gfp_mask); if (newpage) { spin_lock(&pagecache_lock); page = __find_lock_page_helper(mapping, index, *hash); if (likely(!page)) { page = newpage; __add_to_page_cache(page, mapping, index, hash); newpage = NULL; } spin_unlock(&pagecache_lock); if (newpage == NULL) lru_cache_add(page); else page_cache_release(newpage); } } return page; } /* * Same as grab_cache_page, but do not wait if the page is unavailable. * This is intended for speculative data generators, where the data can * be regenerated if the page couldn't be grabbed. This routine should * be safe to call while holding the lock for another page. */ struct page *grab_cache_page_nowait(struct address_space *mapping, unsigned long index) { struct page *page, **hash; hash = page_hash(mapping, index); page = __find_get_page(mapping, index, hash); if ( page ) { if ( !TryLockPage(page) ) { /* Page found and locked */ /* This test is overly paranoid, but what the heck... */ if ( unlikely(page->mapping != mapping || page->index != index) ) { /* Someone reallocated this page under us. */ UnlockPage(page); page_cache_release(page); return NULL; } else { return page; } } else { /* Page locked by someone else */ page_cache_release(page); return NULL; } } page = page_cache_alloc(mapping); if ( unlikely(!page) ) return NULL; /* Failed to allocate a page */ if ( unlikely(add_to_page_cache_unique(page, mapping, index, hash)) ) { /* Someone else grabbed the page already. */ page_cache_release(page); return NULL; } return page; } #if 0 #define PROFILE_READAHEAD #define DEBUG_READAHEAD #endif /* * Read-ahead profiling information * -------------------------------- * Every PROFILE_MAXREADCOUNT, the following information is written * to the syslog: * Percentage of asynchronous read-ahead. * Average of read-ahead fields context value. * If DEBUG_READAHEAD is defined, a snapshot of these fields is written * to the syslog. */ #ifdef PROFILE_READAHEAD #define PROFILE_MAXREADCOUNT 1000 static unsigned long total_reada; static unsigned long total_async; static unsigned long total_ramax; static unsigned long total_ralen; static unsigned long total_rawin; static void profile_readahead(int async, struct file *filp) { unsigned long flags; ++total_reada; if (async) ++total_async; total_ramax += filp->f_ramax; total_ralen += filp->f_ralen; total_rawin += filp->f_rawin; if (total_reada > PROFILE_MAXREADCOUNT) { save_flags(flags); cli(); if (!(total_reada > PROFILE_MAXREADCOUNT)) { restore_flags(flags); return; } printk("Readahead average: max=%ld, len=%ld, win=%ld, async=%ld%%\n", total_ramax/total_reada, total_ralen/total_reada, total_rawin/total_reada, (total_async*100)/total_reada); #ifdef DEBUG_READAHEAD printk("Readahead snapshot: max=%ld, len=%ld, win=%ld, raend=%Ld\n", filp->f_ramax, filp->f_ralen, filp->f_rawin, filp->f_raend); #endif total_reada = 0; total_async = 0; total_ramax = 0; total_ralen = 0; total_rawin = 0; restore_flags(flags); } } #endif /* defined PROFILE_READAHEAD */ /* * Read-ahead context: * ------------------- * The read ahead context fields of the "struct file" are the following: * - f_raend : position of the first byte after the last page we tried to * read ahead. * - f_ramax : current read-ahead maximum size. * - f_ralen : length of the current IO read block we tried to read-ahead. * - f_rawin : length of the current read-ahead window. * if last read-ahead was synchronous then * f_rawin = f_ralen * otherwise (was asynchronous) * f_rawin = previous value of f_ralen + f_ralen * * Read-ahead limits: * ------------------ * MIN_READAHEAD : minimum read-ahead size when read-ahead. * MAX_READAHEAD : maximum read-ahead size when read-ahead. * * Synchronous read-ahead benefits: * -------------------------------- * Using reasonable IO xfer length from peripheral devices increase system * performances. * Reasonable means, in this context, not too large but not too small. * The actual maximum value is: * MAX_READAHEAD + PAGE_CACHE_SIZE = 76k is CONFIG_READA_SMALL is undefined * and 32K if defined (4K page size assumed). * * Asynchronous read-ahead benefits: * --------------------------------- * Overlapping next read request and user process execution increase system * performance. * * Read-ahead risks: * ----------------- * We have to guess which further data are needed by the user process. * If these data are often not really needed, it's bad for system * performances. * However, we know that files are often accessed sequentially by * application programs and it seems that it is possible to have some good * strategy in that guessing. * We only try to read-ahead files that seems to be read sequentially. * * Asynchronous read-ahead risks: * ------------------------------ * In order to maximize overlapping, we must start some asynchronous read * request from the device, as soon as possible. * We must be very careful about: * - The number of effective pending IO read requests. * ONE seems to be the only reasonable value. * - The total memory pool usage for the file access stream. * This maximum memory usage is implicitly 2 IO read chunks: * 2*(MAX_READAHEAD + PAGE_CACHE_SIZE) = 156K if CONFIG_READA_SMALL is undefined, * 64k if defined (4K page size assumed). */ static inline int get_max_readahead(struct inode * inode) { if (!inode->i_dev || !max_readahead[MAJOR(inode->i_dev)]) return vm_max_readahead; return max_readahead[MAJOR(inode->i_dev)][MINOR(inode->i_dev)]; } static void generic_file_readahead(int reada_ok, struct file * filp, struct inode * inode, struct page * page) { unsigned long end_index; unsigned long index = page->index; unsigned long max_ahead, ahead; unsigned long raend; int max_readahead = get_max_readahead(inode); end_index = inode->i_size >> PAGE_CACHE_SHIFT; raend = filp->f_raend; max_ahead = 0; /* * The current page is locked. * If the current position is inside the previous read IO request, do not * try to reread previously read ahead pages. * Otherwise decide or not to read ahead some pages synchronously. * If we are not going to read ahead, set the read ahead context for this * page only. */ if (PageLocked(page)) { if (!filp->f_ralen || index >= raend || index + filp->f_rawin < raend) { raend = index; if (raend < end_index) max_ahead = filp->f_ramax; filp->f_rawin = 0; filp->f_ralen = 1; if (!max_ahead) { filp->f_raend = index + filp->f_ralen; filp->f_rawin += filp->f_ralen; } } } /* * The current page is not locked. * If we were reading ahead and, * if the current max read ahead size is not zero and, * if the current position is inside the last read-ahead IO request, * it is the moment to try to read ahead asynchronously. * We will later force unplug device in order to force asynchronous read IO. */ else if (reada_ok && filp->f_ramax && raend >= 1 && index <= raend && index + filp->f_ralen >= raend) { /* * Add ONE page to max_ahead in order to try to have about the same IO max size * as synchronous read-ahead (MAX_READAHEAD + 1)*PAGE_CACHE_SIZE. * Compute the position of the last page we have tried to read in order to * begin to read ahead just at the next page. */ raend -= 1; if (raend < end_index) max_ahead = filp->f_ramax + 1; if (max_ahead) { filp->f_rawin = filp->f_ralen; filp->f_ralen = 0; reada_ok = 2; } } /* * Try to read ahead pages. * We hope that ll_rw_blk() plug/unplug, coalescence, requests sort and the * scheduler, will work enough for us to avoid too bad actuals IO requests. */ ahead = 0; while (ahead < max_ahead) { unsigned long ra_index = raend + ahead + 1; if (ra_index >= end_index) break; if (page_cache_read(filp, ra_index) < 0) break; ahead++; } /* * If we tried to read ahead some pages, * If we tried to read ahead asynchronously, * Try to force unplug of the device in order to start an asynchronous * read IO request. * Update the read-ahead context. * Store the length of the current read-ahead window. * Double the current max read ahead size. * That heuristic avoid to do some large IO for files that are not really * accessed sequentially. */ if (ahead) { filp->f_ralen += ahead; filp->f_rawin += filp->f_ralen; filp->f_raend = raend + ahead + 1; filp->f_ramax += filp->f_ramax; if (filp->f_ramax > max_readahead) filp->f_ramax = max_readahead; #ifdef PROFILE_READAHEAD profile_readahead((reada_ok == 2), filp); #endif } return; } /* * Mark a page as having seen activity. * * If it was already so marked, move it to the active queue and drop * the referenced bit. Otherwise, just mark it for future action.. */ void mark_page_accessed(struct page *page) { if (!PageActive(page) && PageReferenced(page)) { activate_page(page); ClearPageReferenced(page); } else SetPageReferenced(page); } /* * This is a generic file read routine, and uses the * inode->i_op->readpage() function for the actual low-level * stuff. * * This is really ugly. But the goto's actually try to clarify some * of the logic when it comes to error handling etc. */ void do_generic_file_read(struct file * filp, loff_t *ppos, read_descriptor_t * desc, read_actor_t actor) { struct address_space *mapping = filp->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; unsigned long index, offset; struct page *cached_page; int reada_ok; int error; int max_readahead = get_max_readahead(inode); cached_page = NULL; index = *ppos >> PAGE_CACHE_SHIFT; offset = *ppos & ~PAGE_CACHE_MASK; /* * If the current position is outside the previous read-ahead window, * we reset the current read-ahead context and set read ahead max to zero * (will be set to just needed value later), * otherwise, we assume that the file accesses are sequential enough to * continue read-ahead. */ if (index > filp->f_raend || index + filp->f_rawin < filp->f_raend) { reada_ok = 0; filp->f_raend = 0; filp->f_ralen = 0; filp->f_ramax = 0; filp->f_rawin = 0; } else { reada_ok = 1; } /* * Adjust the current value of read-ahead max. * If the read operation stay in the first half page, force no readahead. * Otherwise try to increase read ahead max just enough to do the read request. * Then, at least MIN_READAHEAD if read ahead is ok, * and at most MAX_READAHEAD in all cases. */ if (!index && offset + desc->count <= (PAGE_CACHE_SIZE >> 1)) { filp->f_ramax = 0; } else { unsigned long needed; needed = ((offset + desc->count) >> PAGE_CACHE_SHIFT) + 1; if (filp->f_ramax < needed) filp->f_ramax = needed; if (reada_ok && filp->f_ramax < vm_min_readahead) filp->f_ramax = vm_min_readahead; if (filp->f_ramax > max_readahead) filp->f_ramax = max_readahead; } for (;;) { struct page *page, **hash; unsigned long end_index, nr, ret; end_index = inode->i_size >> PAGE_CACHE_SHIFT; if (index > end_index) break; nr = PAGE_CACHE_SIZE; if (index == end_index) { nr = inode->i_size & ~PAGE_CACHE_MASK; if (nr <= offset) break; } nr = nr - offset; /* * Try to find the data in the page cache.. */ hash = page_hash(mapping, index); spin_lock(&pagecache_lock); page = __find_page_nolock(mapping, index, *hash); if (!page) goto no_cached_page; found_page: page_cache_get(page); spin_unlock(&pagecache_lock); if (!Page_Uptodate(page)) goto page_not_up_to_date; generic_file_readahead(reada_ok, filp, inode, page); page_ok: /* If users can be writing to this page using arbitrary * virtual addresses, take care about potential aliasing * before reading the page on the kernel side. */ if (mapping->i_mmap_shared != NULL) flush_dcache_page(page); /* * Mark the page accessed if we read the * beginning or we just did an lseek. */ if (!offset || !filp->f_reada) mark_page_accessed(page); /* * Ok, we have the page, and it's up-to-date, so * now we can copy it to user space... * * The actor routine returns how many bytes were actually used.. * NOTE! This may not be the same as how much of a user buffer * we filled up (we may be padding etc), so we can only update * "pos" here (the actor routine has to update the user buffer * pointers and the remaining count). */ ret = actor(desc, page, offset, nr); offset += ret; index += offset >> PAGE_CACHE_SHIFT; offset &= ~PAGE_CACHE_MASK; page_cache_release(page); if (ret == nr && desc->count) continue; break; /* * Ok, the page was not immediately readable, so let's try to read ahead while we're at it.. */ page_not_up_to_date: generic_file_readahead(reada_ok, filp, inode, page); if (Page_Uptodate(page)) goto page_ok; /* Get exclusive access to the page ... */ lock_page(page); /* Did it get unhashed before we got the lock? */ if (!page->mapping) { UnlockPage(page); page_cache_release(page); continue; } /* Did somebody else fill it already? */ if (Page_Uptodate(page)) { UnlockPage(page); goto page_ok; } readpage: /* ... and start the actual read. The read will unlock the page. */ error = mapping->a_ops->readpage(filp, page); if (!error) { if (Page_Uptodate(page)) goto page_ok; /* Again, try some read-ahead while waiting for the page to finish.. */ generic_file_readahead(reada_ok, filp, inode, page); wait_on_page(page); if (Page_Uptodate(page)) goto page_ok; error = -EIO; } /* UHHUH! A synchronous read error occurred. Report it */ desc->error = error; page_cache_release(page); break; no_cached_page: /* * Ok, it wasn't cached, so we need to create a new * page.. * * We get here with the page cache lock held. */ if (!cached_page) { spin_unlock(&pagecache_lock); cached_page = page_cache_alloc(mapping); if (!cached_page) { desc->error = -ENOMEM; break; } /* * Somebody may have added the page while we * dropped the page cache lock. Check for that. */ spin_lock(&pagecache_lock); page = __find_page_nolock(mapping, index, *hash); if (page) goto found_page; } /* * Ok, add the new page to the hash-queues... */ page = cached_page; __add_to_page_cache(page, mapping, index, hash); spin_unlock(&pagecache_lock); lru_cache_add(page); cached_page = NULL; goto readpage; } *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset; filp->f_reada = 1; if (cached_page) page_cache_release(cached_page); UPDATE_ATIME(inode); } static inline int have_mapping_directIO(struct address_space * mapping) { return mapping->a_ops->direct_IO || mapping->a_ops->direct_fileIO; } /* Switch between old and new directIO formats */ static inline int do_call_directIO(int rw, struct file *filp, struct kiobuf *iobuf, unsigned long offset, int blocksize) { struct address_space * mapping = filp->f_dentry->d_inode->i_mapping; if (mapping->a_ops->direct_fileIO) return mapping->a_ops->direct_fileIO(rw, filp, iobuf, offset, blocksize); return mapping->a_ops->direct_IO(rw, mapping->host, iobuf, offset, blocksize); } /* * i_sem and i_alloc_sem should be held already. i_sem may be dropped * later once we've mapped the new IO. i_alloc_sem is kept until the IO * completes. */ static ssize_t generic_file_direct_IO(int rw, struct file * filp, char * buf, size_t count, loff_t offset) { ssize_t retval; int new_iobuf, chunk_size, blocksize_mask, blocksize, blocksize_bits, iosize, progress; struct kiobuf * iobuf; struct address_space * mapping = filp->f_dentry->d_inode->i_mapping; struct inode * inode = mapping->host; loff_t size = inode->i_size; new_iobuf = 0; iobuf = filp->f_iobuf; if (test_and_set_bit(0, &filp->f_iobuf_lock)) { /* * A parallel read/write is using the preallocated iobuf * so just run slow and allocate a new one. */ retval = alloc_kiovec(1, &iobuf); if (retval) goto out; new_iobuf = 1; } blocksize = 1 << inode->i_blkbits; blocksize_bits = inode->i_blkbits; blocksize_mask = blocksize - 1; chunk_size = KIO_MAX_ATOMIC_IO << 10; retval = -EINVAL; if ((offset & blocksize_mask) || (count & blocksize_mask) || ((unsigned long) buf & blocksize_mask)) goto out_free; if (!have_mapping_directIO(mapping)) goto out_free; if ((rw == READ) && (offset + count > size)) count = size - offset; /* * Flush to disk exclusively the _data_, metadata must remain * completly asynchronous or performance will go to /dev/null. */ retval = filemap_fdatasync(mapping); if (retval == 0) retval = fsync_inode_data_buffers(inode); if (retval == 0) retval = filemap_fdatawait(mapping); if (retval < 0) goto out_free; progress = retval = 0; while (count > 0) { iosize = count; if (iosize > chunk_size) iosize = chunk_size; retval = map_user_kiobuf(rw, iobuf, (unsigned long) buf, iosize); if (retval) break; retval = do_call_directIO(rw, filp, iobuf, (offset+progress) >> blocksize_bits, blocksize); if (rw == READ && retval > 0) mark_dirty_kiobuf(iobuf, retval); if (retval >= 0) { count -= retval; buf += retval; /* warning: weird semantics here, we're reporting a read behind the end of the file */ progress += retval; } unmap_kiobuf(iobuf); if (retval != iosize) break; } if (progress) retval = progress; out_free: if (!new_iobuf) clear_bit(0, &filp->f_iobuf_lock); else free_kiovec(1, &iobuf); out: return retval; } int file_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size) { char *kaddr; unsigned long left, count = desc->count; if (size > count) size = count; kaddr = kmap(page); left = __copy_to_user(desc->buf, kaddr + offset, size); kunmap(page); if (left) { size -= left; desc->error = -EFAULT; } desc->count = count - size; desc->written += size; desc->buf += size; return size; } inline ssize_t do_generic_direct_read(struct file * filp, char * buf, size_t count, loff_t *ppos) { ssize_t retval; loff_t pos = *ppos; retval = generic_file_direct_IO(READ, filp, buf, count, pos); if (retval > 0) *ppos = pos + retval; return retval; } /* * This is the "read()" routine for all filesystems * that can use the page cache directly. */ ssize_t generic_file_read(struct file * filp, char * buf, size_t count, loff_t *ppos) { ssize_t retval; if ((ssize_t) count < 0) return -EINVAL; if (filp->f_flags & O_DIRECT) goto o_direct; retval = -EFAULT; if (access_ok(VERIFY_WRITE, buf, count)) { retval = 0; if (count) { read_descriptor_t desc; desc.written = 0; desc.count = count; desc.buf = buf; desc.error = 0; do_generic_file_read(filp, ppos, &desc, file_read_actor); retval = desc.written; if (!retval) retval = desc.error; } } out: return retval; o_direct: { loff_t size; struct address_space *mapping = filp->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; retval = 0; if (!count) goto out; /* skip atime */ down_read(&inode->i_alloc_sem); down(&inode->i_sem); size = inode->i_size; if (*ppos < size) retval = do_generic_direct_read(filp, buf, count, ppos); up(&inode->i_sem); up_read(&inode->i_alloc_sem); UPDATE_ATIME(filp->f_dentry->d_inode); goto out; } } static int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset , unsigned long size) { ssize_t written; unsigned long count = desc->count; struct file *file = (struct file *) desc->buf; if (size > count) size = count; if (file->f_op->sendpage) { written = file->f_op->sendpage(file, page, offset, size, &file->f_pos, size<count); } else { char *kaddr; mm_segment_t old_fs; old_fs = get_fs(); set_fs(KERNEL_DS); kaddr = kmap(page); written = file->f_op->write(file, kaddr + offset, size, &file->f_pos); kunmap(page); set_fs(old_fs); } if (written < 0) { desc->error = written; written = 0; } desc->count = count - written; desc->written += written; return written; } static ssize_t common_sendfile(int out_fd, int in_fd, loff_t *offset, size_t count) { ssize_t retval; struct file * in_file, * out_file; struct inode * in_inode, * out_inode; /* * Get input file, and verify that it is ok.. */ retval = -EBADF; in_file = fget(in_fd); if (!in_file) goto out; if (!(in_file->f_mode & FMODE_READ)) goto fput_in; retval = -EINVAL; in_inode = in_file->f_dentry->d_inode; if (!in_inode) goto fput_in; if (!in_inode->i_mapping->a_ops->readpage) goto fput_in; retval = locks_verify_area(FLOCK_VERIFY_READ, in_inode, in_file, in_file->f_pos, count); if (retval) goto fput_in; /* * Get output file, and verify that it is ok.. */ retval = -EBADF; out_file = fget(out_fd); if (!out_file) goto fput_in; if (!(out_file->f_mode & FMODE_WRITE)) goto fput_out; retval = -EINVAL; if (!out_file->f_op || !out_file->f_op->write) goto fput_out; out_inode = out_file->f_dentry->d_inode; retval = locks_verify_area(FLOCK_VERIFY_WRITE, out_inode, out_file, out_file->f_pos, count); if (retval) goto fput_out; retval = 0; if (count) { read_descriptor_t desc; if (!offset) offset = &in_file->f_pos; desc.written = 0; desc.count = count; desc.buf = (char *) out_file; desc.error = 0; do_generic_file_read(in_file, offset, &desc, file_send_actor); retval = desc.written; if (!retval) retval = desc.error; } fput_out: fput(out_file); fput_in: fput(in_file); out: return retval; } asmlinkage ssize_t sys_sendfile(int out_fd, int in_fd, off_t *offset, size_t count) { loff_t pos, *ppos = NULL; ssize_t ret; if (offset) { off_t off; if (unlikely(get_user(off, offset))) return -EFAULT; pos = off; ppos = &pos; } ret = common_sendfile(out_fd, in_fd, ppos, count); if (offset) put_user((off_t)pos, offset); return ret; } asmlinkage ssize_t sys_sendfile64(int out_fd, int in_fd, loff_t *offset, size_t count) { loff_t pos, *ppos = NULL; ssize_t ret; if (offset) { if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t)))) return -EFAULT; ppos = &pos; } ret = common_sendfile(out_fd, in_fd, ppos, count); if (offset) put_user(pos, offset); return ret; } static ssize_t do_readahead(struct file *file, unsigned long index, unsigned long nr) { struct address_space *mapping = file->f_dentry->d_inode->i_mapping; unsigned long max; if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) return -EINVAL; /* Limit it to the size of the file.. */ max = (mapping->host->i_size + ~PAGE_CACHE_MASK) >> PAGE_CACHE_SHIFT; if (index > max) return 0; max -= index; if (nr > max) nr = max; /* And limit it to a sane percentage of the inactive list.. */ max = (nr_free_pages() + nr_inactive_pages) / 2; if (nr > max) nr = max; while (nr) { page_cache_read(file, index); index++; nr--; } return 0; } asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count) { ssize_t ret; struct file *file; ret = -EBADF; file = fget(fd); if (file) { if (file->f_mode & FMODE_READ) { unsigned long start = offset >> PAGE_CACHE_SHIFT; unsigned long len = (count + ((long)offset & ~PAGE_CACHE_MASK)) >> PAGE_CACHE_SHIFT; ret = do_readahead(file, start, len); } fput(file); } return ret; } /* * Read-ahead and flush behind for MADV_SEQUENTIAL areas. Since we are * sure this is sequential access, we don't need a flexible read-ahead * window size -- we can always use a large fixed size window. */ static void nopage_sequential_readahead(struct vm_area_struct * vma, unsigned long pgoff, unsigned long filesize) { unsigned long ra_window; ra_window = get_max_readahead(vma->vm_file->f_dentry->d_inode); ra_window = CLUSTER_OFFSET(ra_window + CLUSTER_PAGES - 1); /* vm_raend is zero if we haven't read ahead in this area yet. */ if (vma->vm_raend == 0) vma->vm_raend = vma->vm_pgoff + ra_window; /* * If we've just faulted the page half-way through our window, * then schedule reads for the next window, and release the * pages in the previous window. */ if ((pgoff + (ra_window >> 1)) == vma->vm_raend) { unsigned long start = vma->vm_pgoff + vma->vm_raend; unsigned long end = start + ra_window; if (end > ((vma->vm_end >> PAGE_SHIFT) + vma->vm_pgoff)) end = (vma->vm_end >> PAGE_SHIFT) + vma->vm_pgoff; if (start > end) return; while ((start < end) && (start < filesize)) { if (read_cluster_nonblocking(vma->vm_file, start, filesize) < 0) break; start += CLUSTER_PAGES; } run_task_queue(&tq_disk); /* if we're far enough past the beginning of this area, recycle pages that are in the previous window. */ if (vma->vm_raend > (vma->vm_pgoff + ra_window + ra_window)) { unsigned long window = ra_window << PAGE_SHIFT; end = vma->vm_start + (vma->vm_raend << PAGE_SHIFT); end -= window + window; filemap_sync(vma, end - window, window, MS_INVALIDATE); } vma->vm_raend += ra_window; } return; } /* * filemap_nopage() is invoked via the vma operations vector for a * mapped memory region to read in file data during a page fault. * * The goto's are kind of ugly, but this streamlines the normal case of having * it in the page cache, and handles the special cases reasonably without * having a lot of duplicated code. */ struct page * filemap_nopage(struct vm_area_struct * area, unsigned long address, int unused) { int error; struct file *file = area->vm_file; struct address_space *mapping = file->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; struct page *page, **hash; unsigned long size, pgoff, endoff; pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff; endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff; retry_all: /* * An external ptracer can access pages that normally aren't * accessible.. */ size = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if ((pgoff >= size) && (area->vm_mm == current->mm)) return NULL; /* The "size" of the file, as far as mmap is concerned, isn't bigger than the mapping */ if (size > endoff) size = endoff; /* * Do we have something in the page cache already? */ hash = page_hash(mapping, pgoff); retry_find: page = __find_get_page(mapping, pgoff, hash); if (!page) goto no_cached_page; /* * Ok, found a page in the page cache, now we need to check * that it's up-to-date. */ if (!Page_Uptodate(page)) goto page_not_uptodate; success: /* * Try read-ahead for sequential areas. */ if (VM_SequentialReadHint(area)) nopage_sequential_readahead(area, pgoff, size); /* * Found the page and have a reference on it, need to check sharing * and possibly copy it over to another page.. */ mark_page_accessed(page); flush_page_to_ram(page); return page; no_cached_page: /* * If the requested offset is within our file, try to read a whole * cluster of pages at once. * * Otherwise, we're off the end of a privately mapped file, * so we need to map a zero page. */ if ((pgoff < size) && !VM_RandomReadHint(area)) error = read_cluster_nonblocking(file, pgoff, size); else error = page_cache_read(file, pgoff); /* * The page we want has now been added to the page cache. * In the unlikely event that someone removed it in the * meantime, we'll just come back here and read it again. */ if (error >= 0) goto retry_find; /* * An error return from page_cache_read can result if the * system is low on memory, or a problem occurs while trying * to schedule I/O. */ if (error == -ENOMEM) return NOPAGE_OOM; return NULL; page_not_uptodate: lock_page(page); /* Did it get unhashed while we waited for it? */ if (!page->mapping) { UnlockPage(page); page_cache_release(page); goto retry_all; } /* Did somebody else get it up-to-date? */ if (Page_Uptodate(page)) { UnlockPage(page); goto success; } if (!mapping->a_ops->readpage(file, page)) { wait_on_page(page); if (Page_Uptodate(page)) goto success; } /* * Umm, take care of errors if the page isn't up-to-date. * Try to re-read it _once_. We do this synchronously, * because there really aren't any performance issues here * and we need to check for errors. */ lock_page(page); /* Somebody truncated the page on us? */ if (!page->mapping) { UnlockPage(page); page_cache_release(page); goto retry_all; } /* Somebody else successfully read it in? */ if (Page_Uptodate(page)) { UnlockPage(page); goto success; } ClearPageError(page); if (!mapping->a_ops->readpage(file, page)) { wait_on_page(page); if (Page_Uptodate(page)) goto success; } /* * Things didn't work out. Return zero to tell the * mm layer so, possibly freeing the page cache page first. */ page_cache_release(page); return NULL; } /* Called with mm->page_table_lock held to protect against other * threads/the swapper from ripping pte's out from under us. */ static inline int filemap_sync_pte(pte_t * ptep, struct vm_area_struct *vma, unsigned long address, unsigned int flags) { pte_t pte = *ptep; if (pte_present(pte)) { struct page *page = pte_page(pte); if (VALID_PAGE(page) && !PageReserved(page) && ptep_test_and_clear_dirty(ptep)) { flush_tlb_page(vma, address); set_page_dirty(page); } } return 0; } static inline int filemap_sync_pte_range(pmd_t * pmd, unsigned long address, unsigned long size, struct vm_area_struct *vma, unsigned long offset, unsigned int flags) { pte_t * pte; unsigned long end; int error; if (pmd_none(*pmd)) return 0; if (pmd_bad(*pmd)) { pmd_ERROR(*pmd); pmd_clear(pmd); return 0; } pte = pte_offset(pmd, address); offset += address & PMD_MASK; address &= ~PMD_MASK; end = address + size; if (end > PMD_SIZE) end = PMD_SIZE; error = 0; do { error |= filemap_sync_pte(pte, vma, address + offset, flags); address += PAGE_SIZE; pte++; } while (address && (address < end)); return error; } static inline int filemap_sync_pmd_range(pgd_t * pgd, unsigned long address, unsigned long size, struct vm_area_struct *vma, unsigned int flags) { pmd_t * pmd; unsigned long offset, end; int error; if (pgd_none(*pgd)) return 0; if (pgd_bad(*pgd)) { pgd_ERROR(*pgd); pgd_clear(pgd); return 0; } pmd = pmd_offset(pgd, address); offset = address & PGDIR_MASK; address &= ~PGDIR_MASK; end = address + size; if (end > PGDIR_SIZE) end = PGDIR_SIZE; error = 0; do { error |= filemap_sync_pte_range(pmd, address, end - address, vma, offset, flags); address = (address + PMD_SIZE) & PMD_MASK; pmd++; } while (address && (address < end)); return error; } int filemap_sync(struct vm_area_struct * vma, unsigned long address, size_t size, unsigned int flags) { pgd_t * dir; unsigned long end = address + size; int error = 0; /* Aquire the lock early; it may be possible to avoid dropping * and reaquiring it repeatedly. */ spin_lock(&vma->vm_mm->page_table_lock); dir = pgd_offset(vma->vm_mm, address); flush_cache_range(vma->vm_mm, end - size, end); if (address >= end) BUG(); do { error |= filemap_sync_pmd_range(dir, address, end - address, vma, flags); address = (address + PGDIR_SIZE) & PGDIR_MASK; dir++; } while (address && (address < end)); flush_tlb_range(vma->vm_mm, end - size, end); spin_unlock(&vma->vm_mm->page_table_lock); return error; } static struct vm_operations_struct generic_file_vm_ops = { nopage: filemap_nopage, }; /* This is used for a general mmap of a disk file */ int generic_file_mmap(struct file * file, struct vm_area_struct * vma) { struct address_space *mapping = file->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) { if (!mapping->a_ops->writepage) return -EINVAL; } if (!mapping->a_ops->readpage) return -ENOEXEC; UPDATE_ATIME(inode); vma->vm_ops = &generic_file_vm_ops; return 0; } /* * The msync() system call. */ /* * MS_SYNC syncs the entire file - including mappings. * * MS_ASYNC initiates writeout of just the dirty mapped data. * This provides no guarantee of file integrity - things like indirect * blocks may not have started writeout. MS_ASYNC is primarily useful * where the application knows that it has finished with the data and * wishes to intelligently schedule its own I/O traffic. */ static int msync_interval(struct vm_area_struct * vma, unsigned long start, unsigned long end, int flags) { int ret = 0; struct file * file = vma->vm_file; if ( (flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED) ) return -EBUSY; if (file && (vma->vm_flags & VM_SHARED)) { ret = filemap_sync(vma, start, end-start, flags); if (!ret && (flags & (MS_SYNC|MS_ASYNC))) { struct inode * inode = file->f_dentry->d_inode; down(&inode->i_sem); ret = filemap_fdatasync(inode->i_mapping); if (flags & MS_SYNC) { int err; if (file->f_op && file->f_op->fsync) { err = file->f_op->fsync(file, file->f_dentry, 1); if (err && !ret) ret = err; } err = filemap_fdatawait(inode->i_mapping); if (err && !ret) ret = err; } up(&inode->i_sem); } } return ret; } asmlinkage long sys_msync(unsigned long start, size_t len, int flags) { unsigned long end; struct vm_area_struct * vma; int unmapped_error, error = -EINVAL; down_read(¤t->mm->mmap_sem); if (start & ~PAGE_MASK) goto out; len = (len + ~PAGE_MASK) & PAGE_MASK; end = start + len; if (end < start) goto out; if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) goto out; if ((flags & MS_ASYNC) && (flags & MS_SYNC)) goto out; error = 0; if (end == start) goto out; /* * If the interval [start,end) covers some unmapped address ranges, * just ignore them, but return -ENOMEM at the end. */ vma = find_vma(current->mm, start); unmapped_error = 0; for (;;) { /* Still start < end. */ error = -ENOMEM; if (!vma) goto out; /* Here start < vma->vm_end. */ if (start < vma->vm_start) { unmapped_error = -ENOMEM; start = vma->vm_start; } /* Here vma->vm_start <= start < vma->vm_end. */ if (end <= vma->vm_end) { if (start < end) { error = msync_interval(vma, start, end, flags); if (error) goto out; } error = unmapped_error; goto out; } /* Here vma->vm_start <= start < vma->vm_end < end. */ error = msync_interval(vma, start, vma->vm_end, flags); if (error) goto out; start = vma->vm_end; vma = vma->vm_next; } out: up_read(¤t->mm->mmap_sem); return error; } static inline void setup_read_behavior(struct vm_area_struct * vma, int behavior) { VM_ClearReadHint(vma); switch(behavior) { case MADV_SEQUENTIAL: vma->vm_flags |= VM_SEQ_READ; break; case MADV_RANDOM: vma->vm_flags |= VM_RAND_READ; break; default: break; } return; } static long madvise_fixup_start(struct vm_area_struct * vma, unsigned long end, int behavior) { struct vm_area_struct * n; struct mm_struct * mm = vma->vm_mm; n = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (!n) return -EAGAIN; *n = *vma; n->vm_end = end; setup_read_behavior(n, behavior); n->vm_raend = 0; if (n->vm_file) get_file(n->vm_file); if (n->vm_ops && n->vm_ops->open) n->vm_ops->open(n); vma->vm_pgoff += (end - vma->vm_start) >> PAGE_SHIFT; lock_vma_mappings(vma); spin_lock(&mm->page_table_lock); vma->vm_start = end; __insert_vm_struct(mm, n); spin_unlock(&mm->page_table_lock); unlock_vma_mappings(vma); return 0; } static long madvise_fixup_end(struct vm_area_struct * vma, unsigned long start, int behavior) { struct vm_area_struct * n; struct mm_struct * mm = vma->vm_mm; n = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (!n) return -EAGAIN; *n = *vma; n->vm_start = start; n->vm_pgoff += (n->vm_start - vma->vm_start) >> PAGE_SHIFT; setup_read_behavior(n, behavior); n->vm_raend = 0; if (n->vm_file) get_file(n->vm_file); if (n->vm_ops && n->vm_ops->open) n->vm_ops->open(n); lock_vma_mappings(vma); spin_lock(&mm->page_table_lock); vma->vm_end = start; __insert_vm_struct(mm, n); spin_unlock(&mm->page_table_lock); unlock_vma_mappings(vma); return 0; } static long madvise_fixup_middle(struct vm_area_struct * vma, unsigned long start, unsigned long end, int behavior) { struct vm_area_struct * left, * right; struct mm_struct * mm = vma->vm_mm; left = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (!left) return -EAGAIN; right = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (!right) { kmem_cache_free(vm_area_cachep, left); return -EAGAIN; } *left = *vma; *right = *vma; left->vm_end = start; right->vm_start = end; right->vm_pgoff += (right->vm_start - left->vm_start) >> PAGE_SHIFT; left->vm_raend = 0; right->vm_raend = 0; if (vma->vm_file) atomic_add(2, &vma->vm_file->f_count); if (vma->vm_ops && vma->vm_ops->open) { vma->vm_ops->open(left); vma->vm_ops->open(right); } vma->vm_pgoff += (start - vma->vm_start) >> PAGE_SHIFT; vma->vm_raend = 0; lock_vma_mappings(vma); spin_lock(&mm->page_table_lock); vma->vm_start = start; vma->vm_end = end; setup_read_behavior(vma, behavior); __insert_vm_struct(mm, left); __insert_vm_struct(mm, right); spin_unlock(&mm->page_table_lock); unlock_vma_mappings(vma); return 0; } /* * We can potentially split a vm area into separate * areas, each area with its own behavior. */ static long madvise_behavior(struct vm_area_struct * vma, unsigned long start, unsigned long end, int behavior) { int error = 0; /* This caps the number of vma's this process can own */ if (vma->vm_mm->map_count > max_map_count) return -ENOMEM; if (start == vma->vm_start) { if (end == vma->vm_end) { setup_read_behavior(vma, behavior); vma->vm_raend = 0; } else error = madvise_fixup_start(vma, end, behavior); } else { if (end == vma->vm_end) error = madvise_fixup_end(vma, start, behavior); else error = madvise_fixup_middle(vma, start, end, behavior); } return error; } /* * Schedule all required I/O operations, then run the disk queue * to make sure they are started. Do not wait for completion. */ static long madvise_willneed(struct vm_area_struct * vma, unsigned long start, unsigned long end) { long error = -EBADF; struct file * file; struct inode * inode; unsigned long size, rlim_rss; /* Doesn't work if there's no mapped file. */ if (!vma->vm_file) return error; file = vma->vm_file; inode = file->f_dentry->d_inode; if (!inode->i_mapping->a_ops->readpage) return error; size = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end; end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; /* Make sure this doesn't exceed the process's max rss. */ error = -EIO; rlim_rss = current->rlim ? current->rlim[RLIMIT_RSS].rlim_cur : LONG_MAX; /* default: see resource.h */ if ((vma->vm_mm->rss + (end - start)) > rlim_rss) return error; /* round to cluster boundaries if this isn't a "random" area. */ if (!VM_RandomReadHint(vma)) { start = CLUSTER_OFFSET(start); end = CLUSTER_OFFSET(end + CLUSTER_PAGES - 1); while ((start < end) && (start < size)) { error = read_cluster_nonblocking(file, start, size); start += CLUSTER_PAGES; if (error < 0) break; } } else { while ((start < end) && (start < size)) { error = page_cache_read(file, start); start++; if (error < 0) break; } } /* Don't wait for someone else to push these requests. */ run_task_queue(&tq_disk); return error; } /* * Application no longer needs these pages. If the pages are dirty, * it's OK to just throw them away. The app will be more careful about * data it wants to keep. Be sure to free swap resources too. The * zap_page_range call sets things up for refill_inactive to actually free * these pages later if no one else has touched them in the meantime, * although we could add these pages to a global reuse list for * refill_inactive to pick up before reclaiming other pages. * * NB: This interface discards data rather than pushes it out to swap, * as some implementations do. This has performance implications for * applications like large transactional databases which want to discard * pages in anonymous maps after committing to backing store the data * that was kept in them. There is no reason to write this data out to * the swap area if the application is discarding it. * * An interface that causes the system to free clean pages and flush * dirty pages is already available as msync(MS_INVALIDATE). */ static long madvise_dontneed(struct vm_area_struct * vma, unsigned long start, unsigned long end) { if (vma->vm_flags & VM_LOCKED) return -EINVAL; zap_page_range(vma->vm_mm, start, end - start); return 0; } static long madvise_vma(struct vm_area_struct * vma, unsigned long start, unsigned long end, int behavior) { long error = -EBADF; switch (behavior) { case MADV_NORMAL: case MADV_SEQUENTIAL: case MADV_RANDOM: error = madvise_behavior(vma, start, end, behavior); break; case MADV_WILLNEED: error = madvise_willneed(vma, start, end); break; case MADV_DONTNEED: error = madvise_dontneed(vma, start, end); break; default: error = -EINVAL; break; } return error; } /* * The madvise(2) system call. * * Applications can use madvise() to advise the kernel how it should * handle paging I/O in this VM area. The idea is to help the kernel * use appropriate read-ahead and caching techniques. The information * provided is advisory only, and can be safely disregarded by the * kernel without affecting the correct operation of the application. * * behavior values: * MADV_NORMAL - the default behavior is to read clusters. This * results in some read-ahead and read-behind. * MADV_RANDOM - the system should read the minimum amount of data * on any access, since it is unlikely that the appli- * cation will need more than what it asks for. * MADV_SEQUENTIAL - pages in the given range will probably be accessed * once, so they can be aggressively read ahead, and * can be freed soon after they are accessed. * MADV_WILLNEED - the application is notifying the system to read * some pages ahead. * MADV_DONTNEED - the application is finished with the given range, * so the kernel can free resources associated with it. * * return values: * zero - success * -EINVAL - start + len < 0, start is not page-aligned, * "behavior" is not a valid value, or application * is attempting to release locked or shared pages. * -ENOMEM - addresses in the specified range are not currently * mapped, or are outside the AS of the process. * -EIO - an I/O error occurred while paging in data. * -EBADF - map exists, but area maps something that isn't a file. * -EAGAIN - a kernel resource was temporarily unavailable. */ asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior) { unsigned long end; struct vm_area_struct * vma; int unmapped_error = 0; int error = -EINVAL; down_write(¤t->mm->mmap_sem); if (start & ~PAGE_MASK) goto out; len = (len + ~PAGE_MASK) & PAGE_MASK; end = start + len; if (end < start) goto out; error = 0; if (end == start) goto out; /* * If the interval [start,end) covers some unmapped address * ranges, just ignore them, but return -ENOMEM at the end. */ vma = find_vma(current->mm, start); for (;;) { /* Still start < end. */ error = -ENOMEM; if (!vma) goto out; /* Here start < vma->vm_end. */ if (start < vma->vm_start) { unmapped_error = -ENOMEM; start = vma->vm_start; } /* Here vma->vm_start <= start < vma->vm_end. */ if (end <= vma->vm_end) { if (start < end) { error = madvise_vma(vma, start, end, behavior); if (error) goto out; } error = unmapped_error; goto out; } /* Here vma->vm_start <= start < vma->vm_end < end. */ error = madvise_vma(vma, start, vma->vm_end, behavior); if (error) goto out; start = vma->vm_end; vma = vma->vm_next; } out: up_write(¤t->mm->mmap_sem); return error; } /* * Later we can get more picky about what "in core" means precisely. * For now, simply check to see if the page is in the page cache, * and is up to date; i.e. that no page-in operation would be required * at this time if an application were to map and access this page. */ static unsigned char mincore_page(struct vm_area_struct * vma, unsigned long pgoff) { unsigned char present = 0; struct address_space * as = vma->vm_file->f_dentry->d_inode->i_mapping; struct page * page, ** hash = page_hash(as, pgoff); spin_lock(&pagecache_lock); page = __find_page_nolock(as, pgoff, *hash); if ((page) && (Page_Uptodate(page))) present = 1; spin_unlock(&pagecache_lock); return present; } static long mincore_vma(struct vm_area_struct * vma, unsigned long start, unsigned long end, unsigned char * vec) { long error, i, remaining; unsigned char * tmp; error = -ENOMEM; if (!vma->vm_file) return error; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end; end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; error = -EAGAIN; tmp = (unsigned char *) __get_free_page(GFP_KERNEL); if (!tmp) return error; /* (end - start) is # of pages, and also # of bytes in "vec */ remaining = (end - start), error = 0; for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) { int j = 0; long thispiece = (remaining < PAGE_SIZE) ? remaining : PAGE_SIZE; while (j < thispiece) tmp[j++] = mincore_page(vma, start++); if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) { error = -EFAULT; break; } } free_page((unsigned long) tmp); return error; } /* * The mincore(2) system call. * * mincore() returns the memory residency status of the pages in the * current process's address space specified by [addr, addr + len). * The status is returned in a vector of bytes. The least significant * bit of each byte is 1 if the referenced page is in memory, otherwise * it is zero. * * Because the status of a page can change after mincore() checks it * but before it returns to the application, the returned vector may * contain stale information. Only locked pages are guaranteed to * remain in memory. * * return values: * zero - success * -EFAULT - vec points to an illegal address * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE, * or len has a nonpositive value * -ENOMEM - Addresses in the range [addr, addr + len] are * invalid for the address space of this process, or * specify one or more pages which are not currently * mapped * -EAGAIN - A kernel resource was temporarily unavailable. */ asmlinkage long sys_mincore(unsigned long start, size_t len, unsigned char * vec) { int index = 0; unsigned long end; struct vm_area_struct * vma; int unmapped_error = 0; long error = -EINVAL; down_read(¤t->mm->mmap_sem); if (start & ~PAGE_CACHE_MASK) goto out; len = (len + ~PAGE_CACHE_MASK) & PAGE_CACHE_MASK; end = start + len; if (end < start) goto out; error = 0; if (end == start) goto out; /* * If the interval [start,end) covers some unmapped address * ranges, just ignore them, but return -ENOMEM at the end. */ vma = find_vma(current->mm, start); for (;;) { /* Still start < end. */ error = -ENOMEM; if (!vma) goto out; /* Here start < vma->vm_end. */ if (start < vma->vm_start) { unmapped_error = -ENOMEM; start = vma->vm_start; } /* Here vma->vm_start <= start < vma->vm_end. */ if (end <= vma->vm_end) { if (start < end) { error = mincore_vma(vma, start, end, &vec[index]); if (error) goto out; } error = unmapped_error; goto out; } /* Here vma->vm_start <= start < vma->vm_end < end. */ error = mincore_vma(vma, start, vma->vm_end, &vec[index]); if (error) goto out; index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT; start = vma->vm_end; vma = vma->vm_next; } out: up_read(¤t->mm->mmap_sem); return error; } static inline struct page *__read_cache_page(struct address_space *mapping, unsigned long index, int (*filler)(void *,struct page*), void *data) { struct page **hash = page_hash(mapping, index); struct page *page, *cached_page = NULL; int err; repeat: page = __find_get_page(mapping, index, hash); if (!page) { if (!cached_page) { cached_page = page_cache_alloc(mapping); if (!cached_page) return ERR_PTR(-ENOMEM); } page = cached_page; if (add_to_page_cache_unique(page, mapping, index, hash)) goto repeat; cached_page = NULL; err = filler(data, page); if (err < 0) { page_cache_release(page); page = ERR_PTR(err); } } if (cached_page) page_cache_release(cached_page); return page; } /* * Read into the page cache. If a page already exists, * and Page_Uptodate() is not set, try to fill the page. */ struct page *read_cache_page(struct address_space *mapping, unsigned long index, int (*filler)(void *,struct page*), void *data) { struct page *page; int err; retry: page = __read_cache_page(mapping, index, filler, data); if (IS_ERR(page)) goto out; mark_page_accessed(page); if (Page_Uptodate(page)) goto out; lock_page(page); if (!page->mapping) { UnlockPage(page); page_cache_release(page); goto retry; } if (Page_Uptodate(page)) { UnlockPage(page); goto out; } err = filler(data, page); if (err < 0) { page_cache_release(page); page = ERR_PTR(err); } out: return page; } static inline struct page * __grab_cache_page(struct address_space *mapping, unsigned long index, struct page **cached_page) { struct page *page, **hash = page_hash(mapping, index); repeat: page = __find_lock_page(mapping, index, hash); if (!page) { if (!*cached_page) { *cached_page = page_cache_alloc(mapping); if (!*cached_page) return NULL; } page = *cached_page; if (add_to_page_cache_unique(page, mapping, index, hash)) goto repeat; *cached_page = NULL; } return page; } inline void remove_suid(struct inode *inode) { unsigned int mode; /* set S_IGID if S_IXGRP is set, and always set S_ISUID */ mode = (inode->i_mode & S_IXGRP)*(S_ISGID/S_IXGRP) | S_ISUID; /* was any of the uid bits set? */ mode &= inode->i_mode; if (mode && !capable(CAP_FSETID)) { inode->i_mode &= ~mode; mark_inode_dirty(inode); } } /* * precheck_file_write(): * Check the conditions on a file descriptor prior to beginning a write * on it. Contains the common precheck code for both buffered and direct * IO. */ int precheck_file_write(struct file *file, struct inode *inode, size_t *count, loff_t *ppos) { ssize_t err; unsigned long limit = current->rlim[RLIMIT_FSIZE].rlim_cur; loff_t pos = *ppos; err = -EINVAL; if (pos < 0) goto out; err = file->f_error; if (err) { file->f_error = 0; goto out; } /* FIXME: this is for backwards compatibility with 2.4 */ if (!S_ISBLK(inode->i_mode) && (file->f_flags & O_APPEND)) *ppos = pos = inode->i_size; /* * Check whether we've reached the file size limit. */ err = -EFBIG; if (!S_ISBLK(inode->i_mode) && limit != RLIM_INFINITY) { if (pos >= limit) { send_sig(SIGXFSZ, current, 0); goto out; } if (pos > 0xFFFFFFFFULL || *count > limit - (u32)pos) { /* send_sig(SIGXFSZ, current, 0); */ *count = limit - (u32)pos; } } /* * LFS rule */ if ( pos + *count > MAX_NON_LFS && !(file->f_flags&O_LARGEFILE)) { if (pos >= MAX_NON_LFS) { send_sig(SIGXFSZ, current, 0); goto out; } if (*count > MAX_NON_LFS - (u32)pos) { /* send_sig(SIGXFSZ, current, 0); */ *count = MAX_NON_LFS - (u32)pos; } } /* * Are we about to exceed the fs block limit ? * * If we have written data it becomes a short write * If we have exceeded without writing data we send * a signal and give them an EFBIG. * * Linus frestrict idea will clean these up nicely.. */ if (!S_ISBLK(inode->i_mode)) { if (pos >= inode->i_sb->s_maxbytes) { if (*count || pos > inode->i_sb->s_maxbytes) { send_sig(SIGXFSZ, current, 0); err = -EFBIG; goto out; } /* zero-length writes at ->s_maxbytes are OK */ } if (pos + *count > inode->i_sb->s_maxbytes) *count = inode->i_sb->s_maxbytes - pos; } else { if (is_read_only(inode->i_rdev)) { err = -EPERM; goto out; } if (pos >= inode->i_size) { if (*count || pos > inode->i_size) { err = -ENOSPC; goto out; } } if (pos + *count > inode->i_size) *count = inode->i_size - pos; } err = 0; out: return err; } /* * Write to a file through the page cache. * * We currently put everything into the page cache prior to writing it. * This is not a problem when writing full pages. With partial pages, * however, we first have to read the data into the cache, then * dirty the page, and finally schedule it for writing. Alternatively, we * could write-through just the portion of data that would go into that * page, but that would kill performance for applications that write data * line by line, and it's prone to race conditions. * * Note that this routine doesn't try to keep track of dirty pages. Each * file system has to do this all by itself, unfortunately. * okir@monad.swb.de */ ssize_t do_generic_file_write(struct file *file,const char *buf,size_t count, loff_t *ppos) { struct address_space *mapping = file->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; loff_t pos; struct page *page, *cached_page; ssize_t written; long status = 0; ssize_t err; unsigned bytes; cached_page = NULL; pos = *ppos; written = 0; err = precheck_file_write(file, inode, &count, &pos); if (err != 0 || count == 0) goto out; remove_suid(inode); inode->i_ctime = inode->i_mtime = CURRENT_TIME; mark_inode_dirty_sync(inode); do { unsigned long index, offset; long page_fault; char *kaddr; /* * Try to find the page in the cache. If it isn't there, * allocate a free page. */ offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */ index = pos >> PAGE_CACHE_SHIFT; bytes = PAGE_CACHE_SIZE - offset; if (bytes > count) bytes = count; /* * Bring in the user page that we will copy from _first_. * Otherwise there's a nasty deadlock on copying from the * same page as we're writing to, without it being marked * up-to-date. */ { volatile unsigned char dummy; __get_user(dummy, buf); __get_user(dummy, buf+bytes-1); } status = -ENOMEM; /* we'll assign it later anyway */ page = __grab_cache_page(mapping, index, &cached_page); if (!page) break; /* We have exclusive IO access to the page.. */ if (!PageLocked(page)) { PAGE_BUG(page); } kaddr = kmap(page); status = mapping->a_ops->prepare_write(file, page, offset, offset+bytes); if (status) goto sync_failure; page_fault = __copy_from_user(kaddr+offset, buf, bytes); flush_dcache_page(page); status = mapping->a_ops->commit_write(file, page, offset, offset+bytes); if (page_fault) goto fail_write; if (!status) status = bytes; if (status >= 0) { written += status; count -= status; pos += status; buf += status; } unlock: kunmap(page); /* Mark it unlocked again and drop the page.. */ SetPageReferenced(page); UnlockPage(page); page_cache_release(page); if (status < 0) break; } while (count); done: *ppos = pos; if (cached_page) page_cache_release(cached_page); /* For now, when the user asks for O_SYNC, we'll actually * provide O_DSYNC. */ if (status >= 0) { if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) status = generic_osync_inode(inode, OSYNC_METADATA|OSYNC_DATA); } err = written ? written : status; out: return err; fail_write: status = -EFAULT; goto unlock; sync_failure: /* * If blocksize < pagesize, prepare_write() may have instantiated a * few blocks outside i_size. Trim these off again. */ kunmap(page); UnlockPage(page); page_cache_release(page); if (pos + bytes > inode->i_size) vmtruncate(inode, inode->i_size); goto done; } ssize_t do_generic_direct_write(struct file *file,const char *buf,size_t count, loff_t *ppos) { struct address_space *mapping = file->f_dentry->d_inode->i_mapping; struct inode *inode = mapping->host; loff_t pos; ssize_t written; long status = 0; ssize_t err; pos = *ppos; written = 0; err = precheck_file_write(file, inode, &count, &pos); if (err != 0 || count == 0) goto out; if (!(file->f_flags & O_DIRECT)) BUG(); remove_suid(inode); inode->i_ctime = inode->i_mtime = CURRENT_TIME; mark_inode_dirty_sync(inode); written = generic_file_direct_IO(WRITE, file, (char *) buf, count, pos); if (written > 0) { loff_t end = pos + written; if (end > inode->i_size && !S_ISBLK(inode->i_mode)) { inode->i_size = end; mark_inode_dirty(inode); } *ppos = end; invalidate_inode_pages2(mapping); } /* * Sync the fs metadata but not the minor inode changes and * of course not the data as we did direct DMA for the IO. */ if (written >= 0 && (file->f_flags & O_SYNC)) status = generic_osync_inode(inode, OSYNC_METADATA); err = written ? written : status; out: return err; } static int do_odirect_fallback(struct file *file, struct inode *inode, const char *buf, size_t count, loff_t *ppos) { ssize_t ret; int err; down(&inode->i_sem); ret = do_generic_file_write(file, buf, count, ppos); if (ret > 0) { err = do_fdatasync(file); if (err) ret = err; } up(&inode->i_sem); return ret; } ssize_t generic_file_write(struct file *file,const char *buf,size_t count, loff_t *ppos) { struct inode *inode = file->f_dentry->d_inode->i_mapping->host; ssize_t err; if ((ssize_t) count < 0) return -EINVAL; if (!access_ok(VERIFY_READ, buf, count)) return -EFAULT; if (file->f_flags & O_DIRECT) { /* do_generic_direct_write may drop i_sem during the actual IO */ down_read(&inode->i_alloc_sem); down(&inode->i_sem); err = do_generic_direct_write(file, buf, count, ppos); up(&inode->i_sem); up_read(&inode->i_alloc_sem); if (unlikely(err == -ENOTBLK)) err = do_odirect_fallback(file, inode, buf, count, ppos); } else { down(&inode->i_sem); err = do_generic_file_write(file, buf, count, ppos); up(&inode->i_sem); } return err; } void __init page_cache_init(unsigned long mempages) { unsigned long htable_size, order; htable_size = mempages; htable_size *= sizeof(struct page *); for(order = 0; (PAGE_SIZE << order) < htable_size; order++) ; do { unsigned long tmp = (PAGE_SIZE << order) / sizeof(struct page *); page_hash_bits = 0; while((tmp >>= 1UL) != 0UL) page_hash_bits++; page_hash_table = (struct page **) __get_free_pages(GFP_ATOMIC, order); } while(page_hash_table == NULL && --order > 0); printk("Page-cache hash table entries: %d (order: %ld, %ld bytes)\n", (1 << page_hash_bits), order, (PAGE_SIZE << order)); if (!page_hash_table) panic("Failed to allocate page hash table\n"); memset((void *)page_hash_table, 0, PAGE_HASH_SIZE * sizeof(struct page *)); }