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[/] [test_project/] [trunk/] [linux_sd_driver/] [mm/] [mincore.c] - Blame information for rev 62

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1 62 marcus.erl
/*
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 *      linux/mm/mincore.c
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 *
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 * Copyright (C) 1994-2006  Linus Torvalds
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 */
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/*
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 * The mincore() system call.
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 */
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#include <linux/slab.h>
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#include <linux/pagemap.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/syscalls.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <asm/uaccess.h>
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#include <asm/pgtable.h>
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/*
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 * Later we can get more picky about what "in core" means precisely.
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 * For now, simply check to see if the page is in the page cache,
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 * and is up to date; i.e. that no page-in operation would be required
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 * at this time if an application were to map and access this page.
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 */
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static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
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{
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        unsigned char present = 0;
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        struct page *page;
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        /*
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         * When tmpfs swaps out a page from a file, any process mapping that
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         * file will not get a swp_entry_t in its pte, but rather it is like
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         * any other file mapping (ie. marked !present and faulted in with
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         * tmpfs's .nopage). So swapped out tmpfs mappings are tested here.
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         *
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         * However when tmpfs moves the page from pagecache and into swapcache,
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         * it is still in core, but the find_get_page below won't find it.
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         * No big deal, but make a note of it.
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         */
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        page = find_get_page(mapping, pgoff);
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        if (page) {
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                present = PageUptodate(page);
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                page_cache_release(page);
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        }
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        return present;
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}
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/*
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 * Do a chunk of "sys_mincore()". We've already checked
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 * all the arguments, we hold the mmap semaphore: we should
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 * just return the amount of info we're asked for.
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 */
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static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages)
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{
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        pgd_t *pgd;
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        pud_t *pud;
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        pmd_t *pmd;
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        pte_t *ptep;
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        spinlock_t *ptl;
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        unsigned long nr;
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        int i;
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        pgoff_t pgoff;
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        struct vm_area_struct *vma = find_vma(current->mm, addr);
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        /*
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         * find_vma() didn't find anything above us, or we're
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         * in an unmapped hole in the address space: ENOMEM.
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         */
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        if (!vma || addr < vma->vm_start)
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                return -ENOMEM;
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        /*
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         * Calculate how many pages there are left in the last level of the
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         * PTE array for our address.
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         */
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        nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1));
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        /*
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         * Don't overrun this vma
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         */
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        nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT);
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        /*
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         * Don't return more than the caller asked for
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         */
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        nr = min(nr, pages);
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        pgd = pgd_offset(vma->vm_mm, addr);
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        if (pgd_none_or_clear_bad(pgd))
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                goto none_mapped;
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        pud = pud_offset(pgd, addr);
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        if (pud_none_or_clear_bad(pud))
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                goto none_mapped;
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        pmd = pmd_offset(pud, addr);
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        if (pmd_none_or_clear_bad(pmd))
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                goto none_mapped;
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        ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
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        for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
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                unsigned char present;
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                pte_t pte = *ptep;
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                if (pte_present(pte)) {
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                        present = 1;
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                } else if (pte_none(pte)) {
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                        if (vma->vm_file) {
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                                pgoff = linear_page_index(vma, addr);
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                                present = mincore_page(vma->vm_file->f_mapping,
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                                                        pgoff);
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                        } else
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                                present = 0;
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                } else if (pte_file(pte)) {
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                        pgoff = pte_to_pgoff(pte);
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                        present = mincore_page(vma->vm_file->f_mapping, pgoff);
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                } else { /* pte is a swap entry */
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                        swp_entry_t entry = pte_to_swp_entry(pte);
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                        if (is_migration_entry(entry)) {
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                                /* migration entries are always uptodate */
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                                present = 1;
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                        } else {
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#ifdef CONFIG_SWAP
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                                pgoff = entry.val;
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                                present = mincore_page(&swapper_space, pgoff);
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#else
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                                WARN_ON(1);
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                                present = 1;
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#endif
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                        }
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                }
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                vec[i] = present;
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        }
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        pte_unmap_unlock(ptep-1, ptl);
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        return nr;
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none_mapped:
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        if (vma->vm_file) {
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                pgoff = linear_page_index(vma, addr);
146
                for (i = 0; i < nr; i++, pgoff++)
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                        vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
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        } else {
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                for (i = 0; i < nr; i++)
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                        vec[i] = 0;
151
        }
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153
        return nr;
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}
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/*
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 * The mincore(2) system call.
158
 *
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 * mincore() returns the memory residency status of the pages in the
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 * current process's address space specified by [addr, addr + len).
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 * The status is returned in a vector of bytes.  The least significant
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 * bit of each byte is 1 if the referenced page is in memory, otherwise
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 * it is zero.
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 *
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 * Because the status of a page can change after mincore() checks it
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 * but before it returns to the application, the returned vector may
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 * contain stale information.  Only locked pages are guaranteed to
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 * remain in memory.
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 *
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 * return values:
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 *  zero    - success
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 *  -EFAULT - vec points to an illegal address
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 *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
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 *  -ENOMEM - Addresses in the range [addr, addr + len] are
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 *              invalid for the address space of this process, or
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 *              specify one or more pages which are not currently
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 *              mapped
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 *  -EAGAIN - A kernel resource was temporarily unavailable.
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 */
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asmlinkage long sys_mincore(unsigned long start, size_t len,
181
        unsigned char __user * vec)
182
{
183
        long retval;
184
        unsigned long pages;
185
        unsigned char *tmp;
186
 
187
        /* Check the start address: needs to be page-aligned.. */
188
        if (start & ~PAGE_CACHE_MASK)
189
                return -EINVAL;
190
 
191
        /* ..and we need to be passed a valid user-space range */
192
        if (!access_ok(VERIFY_READ, (void __user *) start, len))
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                return -ENOMEM;
194
 
195
        /* This also avoids any overflows on PAGE_CACHE_ALIGN */
196
        pages = len >> PAGE_SHIFT;
197
        pages += (len & ~PAGE_MASK) != 0;
198
 
199
        if (!access_ok(VERIFY_WRITE, vec, pages))
200
                return -EFAULT;
201
 
202
        tmp = (void *) __get_free_page(GFP_USER);
203
        if (!tmp)
204
                return -EAGAIN;
205
 
206
        retval = 0;
207
        while (pages) {
208
                /*
209
                 * Do at most PAGE_SIZE entries per iteration, due to
210
                 * the temporary buffer size.
211
                 */
212
                down_read(&current->mm->mmap_sem);
213
                retval = do_mincore(start, tmp, min(pages, PAGE_SIZE));
214
                up_read(&current->mm->mmap_sem);
215
 
216
                if (retval <= 0)
217
                        break;
218
                if (copy_to_user(vec, tmp, retval)) {
219
                        retval = -EFAULT;
220
                        break;
221
                }
222
                pages -= retval;
223
                vec += retval;
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                start += retval << PAGE_SHIFT;
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                retval = 0;
226
        }
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        free_page((unsigned long) tmp);
228
        return retval;
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}

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