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/*

 *  linux/fs/file.c

 *

 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes

 *

 *  Manage the dynamic fd arrays in the process files_struct.

 */

#include <linux/fs.h>

#include <linux/mm.h>

#include <linux/time.h>

#include <linux/slab.h>

#include <linux/vmalloc.h>

#include <linux/file.h>

#include <linux/bitops.h>

#include <linux/interrupt.h>

#include <linux/spinlock.h>

#include <linux/rcupdate.h>

#include <linux/workqueue.h>

struct fdtable_defer {

        spinlock_t lock;

        struct work_struct wq;

        struct fdtable *next;

};

/*

 * We use this list to defer free fdtables that have vmalloced

 * sets/arrays. By keeping a per-cpu list, we avoid having to embed

 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in

 * this per-task structure.

 */

static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);

static inline void * alloc_fdmem(unsigned int size)

{

        if (size <= PAGE_SIZE)

                return kmalloc(size, GFP_KERNEL);

        else

                return vmalloc(size);

}

static inline void free_fdarr(struct fdtable *fdt)

{

        if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *)))

                kfree(fdt->fd);

        else

                vfree(fdt->fd);

}

static inline void free_fdset(struct fdtable *fdt)

{

        if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2))

                kfree(fdt->open_fds);

        else

                vfree(fdt->open_fds);

}

static void free_fdtable_work(struct work_struct *work)

{

        struct fdtable_defer *f =

                container_of(work, struct fdtable_defer, wq);

        struct fdtable *fdt;

        spin_lock_bh(&f->lock);

        fdt = f->next;

        f->next = NULL;

        spin_unlock_bh(&f->lock);

        while(fdt) {

                struct fdtable *next = fdt->next;

                vfree(fdt->fd);

                free_fdset(fdt);

                kfree(fdt);

                fdt = next;

        }

}

void free_fdtable_rcu(struct rcu_head *rcu)

{

        struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);

        struct fdtable_defer *fddef;

        BUG_ON(!fdt);

        if (fdt->max_fds <= NR_OPEN_DEFAULT) {

                /*

                 * This fdtable is embedded in the files structure and that

                 * structure itself is getting destroyed.

                 */

                kmem_cache_free(files_cachep,

                                container_of(fdt, struct files_struct, fdtab));

                return;

        }

        if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) {

                kfree(fdt->fd);

                kfree(fdt->open_fds);

                kfree(fdt);

        } else {

                fddef = &get_cpu_var(fdtable_defer_list);

                spin_lock(&fddef->lock);

                fdt->next = fddef->next;

                fddef->next = fdt;

                /* vmallocs are handled from the workqueue context */

                schedule_work(&fddef->wq);

                spin_unlock(&fddef->lock);

                put_cpu_var(fdtable_defer_list);

        }

}

/*

 * Expand the fdset in the files_struct.  Called with the files spinlock

 * held for write.

 */

static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)

{

        unsigned int cpy, set;

        BUG_ON(nfdt->max_fds < ofdt->max_fds);

        if (ofdt->max_fds == 0)

                return;

        cpy = ofdt->max_fds * sizeof(struct file *);

        set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);

        memcpy(nfdt->fd, ofdt->fd, cpy);

        memset((char *)(nfdt->fd) + cpy, 0, set);

        cpy = ofdt->max_fds / BITS_PER_BYTE;

        set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;

        memcpy(nfdt->open_fds, ofdt->open_fds, cpy);

        memset((char *)(nfdt->open_fds) + cpy, 0, set);

        memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);

        memset((char *)(nfdt->close_on_exec) + cpy, 0, set);

}

static struct fdtable * alloc_fdtable(unsigned int nr)

{

        struct fdtable *fdt;

        char *data;

        /*

         * Figure out how many fds we actually want to support in this fdtable.

         * Allocation steps are keyed to the size of the fdarray, since it

         * grows far faster than any of the other dynamic data. We try to fit

         * the fdarray into comfortable page-tuned chunks: starting at 1024B

         * and growing in powers of two from there on.

         */

        nr /= (1024 / sizeof(struct file *));

        nr = roundup_pow_of_two(nr + 1);

        nr *= (1024 / sizeof(struct file *));

        if (nr > NR_OPEN)

                nr = NR_OPEN;

        fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);

        if (!fdt)

                goto out;

        fdt->max_fds = nr;

        data = alloc_fdmem(nr * sizeof(struct file *));

        if (!data)

                goto out_fdt;

        fdt->fd = (struct file **)data;

        data = alloc_fdmem(max_t(unsigned int,

                                 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));

        if (!data)

                goto out_arr;

        fdt->open_fds = (fd_set *)data;

        data += nr / BITS_PER_BYTE;

        fdt->close_on_exec = (fd_set *)data;

        INIT_RCU_HEAD(&fdt->rcu);

        fdt->next = NULL;

        return fdt;

out_arr:

        free_fdarr(fdt);

out_fdt:

        kfree(fdt);

out:

        return NULL;

}

/*

 * Expand the file descriptor table.

 * This function will allocate a new fdtable and both fd array and fdset, of

 * the given size.

 * Return <0 error code on error; 1 on successful completion.

 * The files->file_lock should be held on entry, and will be held on exit.

 */

static int expand_fdtable(struct files_struct *files, int nr)

        __releases(files->file_lock)

        __acquires(files->file_lock)

{

        struct fdtable *new_fdt, *cur_fdt;

        spin_unlock(&files->file_lock);

        new_fdt = alloc_fdtable(nr);

        spin_lock(&files->file_lock);

        if (!new_fdt)

                return -ENOMEM;

        /*

         * Check again since another task may have expanded the fd table while

         * we dropped the lock

         */

        cur_fdt = files_fdtable(files);

        if (nr >= cur_fdt->max_fds) {

                /* Continue as planned */

                copy_fdtable(new_fdt, cur_fdt);

                rcu_assign_pointer(files->fdt, new_fdt);

                if (cur_fdt->max_fds > NR_OPEN_DEFAULT)

                        free_fdtable(cur_fdt);

        } else {

                /* Somebody else expanded, so undo our attempt */

                free_fdarr(new_fdt);

                free_fdset(new_fdt);

                kfree(new_fdt);

        }

        return 1;

}

/*

 * Expand files.

 * This function will expand the file structures, if the requested size exceeds

 * the current capacity and there is room for expansion.

 * Return <0 error code on error; 0 when nothing done; 1 when files were

 * expanded and execution may have blocked.

 * The files->file_lock should be held on entry, and will be held on exit.

 */

int expand_files(struct files_struct *files, int nr)

{

        struct fdtable *fdt;

        fdt = files_fdtable(files);

        /* Do we need to expand? */

        if (nr < fdt->max_fds)

                return 0;

        /* Can we expand? */

        if (nr >= NR_OPEN)

                return -EMFILE;

        /* All good, so we try */

        return expand_fdtable(files, nr);

}

static void __devinit fdtable_defer_list_init(int cpu)

{

        struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);

        spin_lock_init(&fddef->lock);

        INIT_WORK(&fddef->wq, free_fdtable_work);

        fddef->next = NULL;

}

void __init files_defer_init(void)

{

        int i;

        for_each_possible_cpu(i)

                fdtable_defer_list_init(i);

}