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https://mirrors.bfsu.edu.cn/git/linux.git
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6d4831c283
Azurit reports large increases in system time after 2.6.36 when running
Apache. It was bisected down to a892e2d7dc
("vfs: use kmalloc()
to allocate fdmem if possible").
That patch caused the vfs to use kmalloc() for very large allocations and
this is causing excessive work (and presumably excessive reclaim) within
the page allocator.
Fix it by falling back to vmalloc() earlier - when the allocation attempt
would have been considered "costly" by reclaim.
Reported-by: azurIt <azurit@pobox.sk>
Tested-by: azurIt <azurit@pobox.sk>
Acked-by: Changli Gao <xiaosuo@gmail.com>
Cc: Americo Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
487 lines
12 KiB
C
487 lines
12 KiB
C
/*
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* linux/fs/file.c
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*
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* Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
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*
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* Manage the dynamic fd arrays in the process files_struct.
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/time.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/bitops.h>
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#include <linux/interrupt.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/workqueue.h>
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struct fdtable_defer {
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spinlock_t lock;
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struct work_struct wq;
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struct fdtable *next;
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};
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int sysctl_nr_open __read_mostly = 1024*1024;
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int sysctl_nr_open_min = BITS_PER_LONG;
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int sysctl_nr_open_max = 1024 * 1024; /* raised later */
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/*
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* We use this list to defer free fdtables that have vmalloced
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* sets/arrays. By keeping a per-cpu list, we avoid having to embed
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* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
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* this per-task structure.
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*/
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static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
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static void *alloc_fdmem(unsigned int size)
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{
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/*
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* Very large allocations can stress page reclaim, so fall back to
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* vmalloc() if the allocation size will be considered "large" by the VM.
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*/
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if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
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void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);
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if (data != NULL)
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return data;
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}
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return vmalloc(size);
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}
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static void free_fdmem(void *ptr)
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{
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is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);
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}
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static void __free_fdtable(struct fdtable *fdt)
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{
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free_fdmem(fdt->fd);
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free_fdmem(fdt->open_fds);
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kfree(fdt);
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}
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static void free_fdtable_work(struct work_struct *work)
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{
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struct fdtable_defer *f =
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container_of(work, struct fdtable_defer, wq);
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struct fdtable *fdt;
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spin_lock_bh(&f->lock);
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fdt = f->next;
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f->next = NULL;
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spin_unlock_bh(&f->lock);
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while(fdt) {
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struct fdtable *next = fdt->next;
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__free_fdtable(fdt);
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fdt = next;
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}
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}
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void free_fdtable_rcu(struct rcu_head *rcu)
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{
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struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
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struct fdtable_defer *fddef;
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BUG_ON(!fdt);
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if (fdt->max_fds <= NR_OPEN_DEFAULT) {
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/*
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* This fdtable is embedded in the files structure and that
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* structure itself is getting destroyed.
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*/
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kmem_cache_free(files_cachep,
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container_of(fdt, struct files_struct, fdtab));
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return;
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}
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if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
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kfree(fdt->fd);
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kfree(fdt->open_fds);
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kfree(fdt);
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} else {
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fddef = &get_cpu_var(fdtable_defer_list);
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spin_lock(&fddef->lock);
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fdt->next = fddef->next;
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fddef->next = fdt;
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/* vmallocs are handled from the workqueue context */
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schedule_work(&fddef->wq);
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spin_unlock(&fddef->lock);
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put_cpu_var(fdtable_defer_list);
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}
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}
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/*
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* Expand the fdset in the files_struct. Called with the files spinlock
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* held for write.
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*/
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static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
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{
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unsigned int cpy, set;
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BUG_ON(nfdt->max_fds < ofdt->max_fds);
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cpy = ofdt->max_fds * sizeof(struct file *);
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set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
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memcpy(nfdt->fd, ofdt->fd, cpy);
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memset((char *)(nfdt->fd) + cpy, 0, set);
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cpy = ofdt->max_fds / BITS_PER_BYTE;
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set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
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memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
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memset((char *)(nfdt->open_fds) + cpy, 0, set);
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memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
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memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
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}
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static struct fdtable * alloc_fdtable(unsigned int nr)
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{
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struct fdtable *fdt;
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char *data;
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/*
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* Figure out how many fds we actually want to support in this fdtable.
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* Allocation steps are keyed to the size of the fdarray, since it
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* grows far faster than any of the other dynamic data. We try to fit
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* the fdarray into comfortable page-tuned chunks: starting at 1024B
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* and growing in powers of two from there on.
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*/
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nr /= (1024 / sizeof(struct file *));
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nr = roundup_pow_of_two(nr + 1);
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nr *= (1024 / sizeof(struct file *));
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/*
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* Note that this can drive nr *below* what we had passed if sysctl_nr_open
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* had been set lower between the check in expand_files() and here. Deal
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* with that in caller, it's cheaper that way.
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*
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* We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
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* bitmaps handling below becomes unpleasant, to put it mildly...
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*/
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if (unlikely(nr > sysctl_nr_open))
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nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
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fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
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if (!fdt)
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goto out;
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fdt->max_fds = nr;
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data = alloc_fdmem(nr * sizeof(struct file *));
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if (!data)
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goto out_fdt;
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fdt->fd = (struct file **)data;
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data = alloc_fdmem(max_t(unsigned int,
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2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
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if (!data)
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goto out_arr;
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fdt->open_fds = (fd_set *)data;
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data += nr / BITS_PER_BYTE;
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fdt->close_on_exec = (fd_set *)data;
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fdt->next = NULL;
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return fdt;
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out_arr:
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free_fdmem(fdt->fd);
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out_fdt:
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kfree(fdt);
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out:
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return NULL;
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}
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/*
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* Expand the file descriptor table.
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* This function will allocate a new fdtable and both fd array and fdset, of
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* the given size.
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* Return <0 error code on error; 1 on successful completion.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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static int expand_fdtable(struct files_struct *files, int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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struct fdtable *new_fdt, *cur_fdt;
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spin_unlock(&files->file_lock);
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new_fdt = alloc_fdtable(nr);
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spin_lock(&files->file_lock);
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if (!new_fdt)
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return -ENOMEM;
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/*
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* extremely unlikely race - sysctl_nr_open decreased between the check in
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* caller and alloc_fdtable(). Cheaper to catch it here...
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*/
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if (unlikely(new_fdt->max_fds <= nr)) {
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__free_fdtable(new_fdt);
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return -EMFILE;
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}
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/*
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* Check again since another task may have expanded the fd table while
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* we dropped the lock
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*/
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cur_fdt = files_fdtable(files);
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if (nr >= cur_fdt->max_fds) {
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/* Continue as planned */
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copy_fdtable(new_fdt, cur_fdt);
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rcu_assign_pointer(files->fdt, new_fdt);
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if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
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free_fdtable(cur_fdt);
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} else {
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/* Somebody else expanded, so undo our attempt */
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__free_fdtable(new_fdt);
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}
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return 1;
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}
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/*
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* Expand files.
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* This function will expand the file structures, if the requested size exceeds
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* the current capacity and there is room for expansion.
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* Return <0 error code on error; 0 when nothing done; 1 when files were
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* expanded and execution may have blocked.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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int expand_files(struct files_struct *files, int nr)
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{
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struct fdtable *fdt;
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fdt = files_fdtable(files);
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/*
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* N.B. For clone tasks sharing a files structure, this test
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* will limit the total number of files that can be opened.
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*/
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if (nr >= rlimit(RLIMIT_NOFILE))
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return -EMFILE;
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/* Do we need to expand? */
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if (nr < fdt->max_fds)
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return 0;
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/* Can we expand? */
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if (nr >= sysctl_nr_open)
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return -EMFILE;
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/* All good, so we try */
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return expand_fdtable(files, nr);
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}
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static int count_open_files(struct fdtable *fdt)
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{
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int size = fdt->max_fds;
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int i;
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/* Find the last open fd */
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for (i = size/(8*sizeof(long)); i > 0; ) {
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if (fdt->open_fds->fds_bits[--i])
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break;
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}
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i = (i+1) * 8 * sizeof(long);
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return i;
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}
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/*
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* Allocate a new files structure and copy contents from the
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* passed in files structure.
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* errorp will be valid only when the returned files_struct is NULL.
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*/
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struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
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{
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struct files_struct *newf;
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struct file **old_fds, **new_fds;
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int open_files, size, i;
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struct fdtable *old_fdt, *new_fdt;
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*errorp = -ENOMEM;
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newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
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if (!newf)
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goto out;
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atomic_set(&newf->count, 1);
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spin_lock_init(&newf->file_lock);
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newf->next_fd = 0;
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new_fdt = &newf->fdtab;
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new_fdt->max_fds = NR_OPEN_DEFAULT;
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new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
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new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
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new_fdt->fd = &newf->fd_array[0];
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new_fdt->next = NULL;
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
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open_files = count_open_files(old_fdt);
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/*
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* Check whether we need to allocate a larger fd array and fd set.
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*/
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while (unlikely(open_files > new_fdt->max_fds)) {
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spin_unlock(&oldf->file_lock);
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if (new_fdt != &newf->fdtab)
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__free_fdtable(new_fdt);
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new_fdt = alloc_fdtable(open_files - 1);
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if (!new_fdt) {
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*errorp = -ENOMEM;
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goto out_release;
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}
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/* beyond sysctl_nr_open; nothing to do */
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if (unlikely(new_fdt->max_fds < open_files)) {
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__free_fdtable(new_fdt);
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*errorp = -EMFILE;
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goto out_release;
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}
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/*
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* Reacquire the oldf lock and a pointer to its fd table
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* who knows it may have a new bigger fd table. We need
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* the latest pointer.
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*/
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
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open_files = count_open_files(old_fdt);
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}
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old_fds = old_fdt->fd;
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new_fds = new_fdt->fd;
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memcpy(new_fdt->open_fds->fds_bits,
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old_fdt->open_fds->fds_bits, open_files/8);
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memcpy(new_fdt->close_on_exec->fds_bits,
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old_fdt->close_on_exec->fds_bits, open_files/8);
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for (i = open_files; i != 0; i--) {
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struct file *f = *old_fds++;
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if (f) {
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get_file(f);
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} else {
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/*
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* The fd may be claimed in the fd bitmap but not yet
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* instantiated in the files array if a sibling thread
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* is partway through open(). So make sure that this
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* fd is available to the new process.
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*/
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FD_CLR(open_files - i, new_fdt->open_fds);
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}
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rcu_assign_pointer(*new_fds++, f);
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}
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spin_unlock(&oldf->file_lock);
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/* compute the remainder to be cleared */
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size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
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/* This is long word aligned thus could use a optimized version */
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memset(new_fds, 0, size);
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if (new_fdt->max_fds > open_files) {
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int left = (new_fdt->max_fds-open_files)/8;
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int start = open_files / (8 * sizeof(unsigned long));
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memset(&new_fdt->open_fds->fds_bits[start], 0, left);
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memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
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}
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rcu_assign_pointer(newf->fdt, new_fdt);
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return newf;
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out_release:
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kmem_cache_free(files_cachep, newf);
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out:
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return NULL;
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}
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static void __devinit fdtable_defer_list_init(int cpu)
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{
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struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
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spin_lock_init(&fddef->lock);
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INIT_WORK(&fddef->wq, free_fdtable_work);
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fddef->next = NULL;
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}
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void __init files_defer_init(void)
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{
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int i;
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for_each_possible_cpu(i)
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fdtable_defer_list_init(i);
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sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
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-BITS_PER_LONG;
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}
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struct files_struct init_files = {
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.count = ATOMIC_INIT(1),
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.fdt = &init_files.fdtab,
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.fdtab = {
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.max_fds = NR_OPEN_DEFAULT,
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.fd = &init_files.fd_array[0],
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.close_on_exec = (fd_set *)&init_files.close_on_exec_init,
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.open_fds = (fd_set *)&init_files.open_fds_init,
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},
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.file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
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};
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/*
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* allocate a file descriptor, mark it busy.
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*/
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int alloc_fd(unsigned start, unsigned flags)
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{
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struct files_struct *files = current->files;
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unsigned int fd;
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int error;
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struct fdtable *fdt;
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spin_lock(&files->file_lock);
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repeat:
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fdt = files_fdtable(files);
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fd = start;
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if (fd < files->next_fd)
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fd = files->next_fd;
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if (fd < fdt->max_fds)
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fd = find_next_zero_bit(fdt->open_fds->fds_bits,
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fdt->max_fds, fd);
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error = expand_files(files, fd);
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if (error < 0)
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goto out;
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/*
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* If we needed to expand the fs array we
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* might have blocked - try again.
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*/
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if (error)
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goto repeat;
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if (start <= files->next_fd)
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files->next_fd = fd + 1;
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FD_SET(fd, fdt->open_fds);
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if (flags & O_CLOEXEC)
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FD_SET(fd, fdt->close_on_exec);
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else
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FD_CLR(fd, fdt->close_on_exec);
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error = fd;
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#if 1
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/* Sanity check */
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if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
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printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
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rcu_assign_pointer(fdt->fd[fd], NULL);
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}
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#endif
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out:
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spin_unlock(&files->file_lock);
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return error;
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}
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int get_unused_fd(void)
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{
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return alloc_fd(0, 0);
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}
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EXPORT_SYMBOL(get_unused_fd);
|