diff options
Diffstat (limited to 'fs/file.c')
-rw-r--r-- | fs/file.c | 484 |
1 files changed, 484 insertions, 0 deletions
diff --git a/fs/file.c b/fs/file.c new file mode 100644 index 00000000..ba3f6053 --- /dev/null +++ b/fs/file.c @@ -0,0 +1,484 @@ +/* + * 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/export.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/mmzone.h> +#include <linux/time.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/vmalloc.h> +#include <linux/file.h> +#include <linux/fdtable.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; +}; + +int sysctl_nr_open __read_mostly = 1024*1024; +int sysctl_nr_open_min = BITS_PER_LONG; +int sysctl_nr_open_max = 1024 * 1024; /* raised later */ + +/* + * 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 void *alloc_fdmem(size_t size) +{ + /* + * Very large allocations can stress page reclaim, so fall back to + * vmalloc() if the allocation size will be considered "large" by the VM. + */ + if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { + void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); + if (data != NULL) + return data; + } + return vmalloc(size); +} + +static void free_fdmem(void *ptr) +{ + is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); +} + +static void __free_fdtable(struct fdtable *fdt) +{ + free_fdmem(fdt->fd); + free_fdmem(fdt->open_fds); + kfree(fdt); +} + +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; + + __free_fdtable(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 (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) { + 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); + + 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; + void *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 *)); + /* + * Note that this can drive nr *below* what we had passed if sysctl_nr_open + * had been set lower between the check in expand_files() and here. Deal + * with that in caller, it's cheaper that way. + * + * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise + * bitmaps handling below becomes unpleasant, to put it mildly... + */ + if (unlikely(nr > sysctl_nr_open)) + nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; + + 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 = data; + + data = alloc_fdmem(max_t(size_t, + 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); + if (!data) + goto out_arr; + fdt->open_fds = data; + data += nr / BITS_PER_BYTE; + fdt->close_on_exec = data; + fdt->next = NULL; + + return fdt; + +out_arr: + free_fdmem(fdt->fd); +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; + /* + * extremely unlikely race - sysctl_nr_open decreased between the check in + * caller and alloc_fdtable(). Cheaper to catch it here... + */ + if (unlikely(new_fdt->max_fds <= nr)) { + __free_fdtable(new_fdt); + return -EMFILE; + } + /* + * 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_fdtable(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); + + /* + * N.B. For clone tasks sharing a files structure, this test + * will limit the total number of files that can be opened. + */ + if (nr >= rlimit(RLIMIT_NOFILE)) + return -EMFILE; + + /* Do we need to expand? */ + if (nr < fdt->max_fds) + return 0; + + /* Can we expand? */ + if (nr >= sysctl_nr_open) + return -EMFILE; + + /* All good, so we try */ + return expand_fdtable(files, nr); +} + +static int count_open_files(struct fdtable *fdt) +{ + int size = fdt->max_fds; + int i; + + /* Find the last open fd */ + for (i = size / BITS_PER_LONG; i > 0; ) { + if (fdt->open_fds[--i]) + break; + } + i = (i + 1) * BITS_PER_LONG; + return i; +} + +/* + * Allocate a new files structure and copy contents from the + * passed in files structure. + * errorp will be valid only when the returned files_struct is NULL. + */ +struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) +{ + struct files_struct *newf; + struct file **old_fds, **new_fds; + int open_files, size, i; + struct fdtable *old_fdt, *new_fdt; + + *errorp = -ENOMEM; + newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); + if (!newf) + goto out; + + atomic_set(&newf->count, 1); + + spin_lock_init(&newf->file_lock); + newf->next_fd = 0; + new_fdt = &newf->fdtab; + new_fdt->max_fds = NR_OPEN_DEFAULT; + new_fdt->close_on_exec = newf->close_on_exec_init; + new_fdt->open_fds = newf->open_fds_init; + new_fdt->fd = &newf->fd_array[0]; + new_fdt->next = NULL; + + spin_lock(&oldf->file_lock); + old_fdt = files_fdtable(oldf); + open_files = count_open_files(old_fdt); + + /* + * Check whether we need to allocate a larger fd array and fd set. + */ + while (unlikely(open_files > new_fdt->max_fds)) { + spin_unlock(&oldf->file_lock); + + if (new_fdt != &newf->fdtab) + __free_fdtable(new_fdt); + + new_fdt = alloc_fdtable(open_files - 1); + if (!new_fdt) { + *errorp = -ENOMEM; + goto out_release; + } + + /* beyond sysctl_nr_open; nothing to do */ + if (unlikely(new_fdt->max_fds < open_files)) { + __free_fdtable(new_fdt); + *errorp = -EMFILE; + goto out_release; + } + + /* + * Reacquire the oldf lock and a pointer to its fd table + * who knows it may have a new bigger fd table. We need + * the latest pointer. + */ + spin_lock(&oldf->file_lock); + old_fdt = files_fdtable(oldf); + open_files = count_open_files(old_fdt); + } + + old_fds = old_fdt->fd; + new_fds = new_fdt->fd; + + memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); + memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); + + for (i = open_files; i != 0; i--) { + struct file *f = *old_fds++; + if (f) { + get_file(f); + } else { + /* + * The fd may be claimed in the fd bitmap but not yet + * instantiated in the files array if a sibling thread + * is partway through open(). So make sure that this + * fd is available to the new process. + */ + __clear_open_fd(open_files - i, new_fdt); + } + rcu_assign_pointer(*new_fds++, f); + } + spin_unlock(&oldf->file_lock); + + /* compute the remainder to be cleared */ + size = (new_fdt->max_fds - open_files) * sizeof(struct file *); + + /* This is long word aligned thus could use a optimized version */ + memset(new_fds, 0, size); + + if (new_fdt->max_fds > open_files) { + int left = (new_fdt->max_fds - open_files) / 8; + int start = open_files / BITS_PER_LONG; + + memset(&new_fdt->open_fds[start], 0, left); + memset(&new_fdt->close_on_exec[start], 0, left); + } + + rcu_assign_pointer(newf->fdt, new_fdt); + + return newf; + +out_release: + kmem_cache_free(files_cachep, newf); +out: + return NULL; +} + +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); + sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) & + -BITS_PER_LONG; +} + +struct files_struct init_files = { + .count = ATOMIC_INIT(1), + .fdt = &init_files.fdtab, + .fdtab = { + .max_fds = NR_OPEN_DEFAULT, + .fd = &init_files.fd_array[0], + .close_on_exec = init_files.close_on_exec_init, + .open_fds = init_files.open_fds_init, + }, + .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock), +}; + +/* + * allocate a file descriptor, mark it busy. + */ +int alloc_fd(unsigned start, unsigned flags) +{ + struct files_struct *files = current->files; + unsigned int fd; + int error; + struct fdtable *fdt; + + spin_lock(&files->file_lock); +repeat: + fdt = files_fdtable(files); + fd = start; + if (fd < files->next_fd) + fd = files->next_fd; + + if (fd < fdt->max_fds) + fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); + + error = expand_files(files, fd); + if (error < 0) + goto out; + + /* + * If we needed to expand the fs array we + * might have blocked - try again. + */ + if (error) + goto repeat; + + if (start <= files->next_fd) + files->next_fd = fd + 1; + + __set_open_fd(fd, fdt); + if (flags & O_CLOEXEC) + __set_close_on_exec(fd, fdt); + else + __clear_close_on_exec(fd, fdt); + error = fd; +#if 1 + /* Sanity check */ + if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { + printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); + rcu_assign_pointer(fdt->fd[fd], NULL); + } +#endif + +out: + spin_unlock(&files->file_lock); + return error; +} + +int get_unused_fd(void) +{ + return alloc_fd(0, 0); +} +EXPORT_SYMBOL(get_unused_fd); |