diff options
Diffstat (limited to 'linux/fs/file.c')
| -rw-r--r-- | linux/fs/file.c | 914 |
1 files changed, 914 insertions, 0 deletions
diff --git a/linux/fs/file.c b/linux/fs/file.c new file mode 100644 index 00000000..93c5f89c --- /dev/null +++ b/linux/fs/file.c @@ -0,0 +1,914 @@ +/* + * 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/syscalls.h> +#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> + +int sysctl_nr_open __read_mostly = 1024*1024; +int sysctl_nr_open_min = BITS_PER_LONG; +/* our max() is unusable in constant expressions ;-/ */ +#define __const_max(x, y) ((x) < (y) ? (x) : (y)) +int sysctl_nr_open_max = __const_max(INT_MAX, ~(size_t)0/sizeof(void *)) & + -BITS_PER_LONG; + +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|__GFP_NORETRY); + if (data != NULL) + return data; + } + return vmalloc(size); +} + +static void __free_fdtable(struct fdtable *fdt) +{ + kvfree(fdt->fd); + kvfree(fdt->open_fds); + kfree(fdt); +} + +static void free_fdtable_rcu(struct rcu_head *rcu) +{ + __free_fdtable(container_of(rcu, struct fdtable, rcu)); +} + +/* + * 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; + + return fdt; + +out_arr: + kvfree(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 != &files->fdtab) + call_rcu(&cur_fdt->rcu, free_fdtable_rcu); + } 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. + */ +static 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 >= sysctl_nr_open) + return -EMFILE; + + /* All good, so we try */ + return expand_fdtable(files, nr); +} + +static inline void __set_close_on_exec(int fd, struct fdtable *fdt) +{ + __set_bit(fd, fdt->close_on_exec); +} + +static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) +{ + __clear_bit(fd, fdt->close_on_exec); +} + +static inline void __set_open_fd(int fd, struct fdtable *fdt) +{ + __set_bit(fd, fdt->open_fds); +} + +static inline void __clear_open_fd(int fd, struct fdtable *fdt) +{ + __clear_bit(fd, fdt->open_fds); +} + +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]; + + 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 struct fdtable *close_files(struct files_struct * files) +{ + /* + * It is safe to dereference the fd table without RCU or + * ->file_lock because this is the last reference to the + * files structure. + */ + struct fdtable *fdt = rcu_dereference_raw(files->fdt); + int i, j = 0; + + for (;;) { + unsigned long set; + i = j * BITS_PER_LONG; + if (i >= fdt->max_fds) + break; + set = fdt->open_fds[j++]; + while (set) { + if (set & 1) { + struct file * file = xchg(&fdt->fd[i], NULL); + if (file) { + filp_close(file, files); + cond_resched_rcu_qs(); + } + } + i++; + set >>= 1; + } + } + + return fdt; +} + +struct files_struct *get_files_struct(struct task_struct *task) +{ + struct files_struct *files; + + task_lock(task); + files = task->files; + if (files) + atomic_inc(&files->count); + task_unlock(task); + + return files; +} + +void put_files_struct(struct files_struct *files) +{ + if (atomic_dec_and_test(&files->count)) { + struct fdtable *fdt = close_files(files); + + /* free the arrays if they are not embedded */ + if (fdt != &files->fdtab) + __free_fdtable(fdt); + kmem_cache_free(files_cachep, files); + } +} + +void reset_files_struct(struct files_struct *files) +{ + struct task_struct *tsk = current; + struct files_struct *old; + + old = tsk->files; + task_lock(tsk); + tsk->files = files; + task_unlock(tsk); + put_files_struct(old); +} + +void exit_files(struct task_struct *tsk) +{ + struct files_struct * files = tsk->files; + + if (files) { + task_lock(tsk); + tsk->files = NULL; + task_unlock(tsk); + put_files_struct(files); + } +} + +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_files.file_lock), +}; + +/* + * allocate a file descriptor, mark it busy. + */ +int __alloc_fd(struct files_struct *files, + unsigned start, unsigned end, unsigned flags) +{ + 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); + + /* + * N.B. For clone tasks sharing a files structure, this test + * will limit the total number of files that can be opened. + */ + error = -EMFILE; + if (fd >= end) + goto out; + + 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_access_pointer(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; +} + +static int alloc_fd(unsigned start, unsigned flags) +{ + return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); +} + +int get_unused_fd_flags(unsigned flags) +{ + return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); +} +EXPORT_SYMBOL(get_unused_fd_flags); + +static void __put_unused_fd(struct files_struct *files, unsigned int fd) +{ + struct fdtable *fdt = files_fdtable(files); + __clear_open_fd(fd, fdt); + if (fd < files->next_fd) + files->next_fd = fd; +} + +void put_unused_fd(unsigned int fd) +{ + struct files_struct *files = current->files; + spin_lock(&files->file_lock); + __put_unused_fd(files, fd); + spin_unlock(&files->file_lock); +} + +EXPORT_SYMBOL(put_unused_fd); + +/* + * Install a file pointer in the fd array. + * + * The VFS is full of places where we drop the files lock between + * setting the open_fds bitmap and installing the file in the file + * array. At any such point, we are vulnerable to a dup2() race + * installing a file in the array before us. We need to detect this and + * fput() the struct file we are about to overwrite in this case. + * + * It should never happen - if we allow dup2() do it, _really_ bad things + * will follow. + * + * NOTE: __fd_install() variant is really, really low-level; don't + * use it unless you are forced to by truly lousy API shoved down + * your throat. 'files' *MUST* be either current->files or obtained + * by get_files_struct(current) done by whoever had given it to you, + * or really bad things will happen. Normally you want to use + * fd_install() instead. + */ + +void __fd_install(struct files_struct *files, unsigned int fd, + struct file *file) +{ + struct fdtable *fdt; + spin_lock(&files->file_lock); + fdt = files_fdtable(files); + BUG_ON(fdt->fd[fd] != NULL); + rcu_assign_pointer(fdt->fd[fd], file); + spin_unlock(&files->file_lock); +} + +void fd_install(unsigned int fd, struct file *file) +{ + __fd_install(current->files, fd, file); +} + +EXPORT_SYMBOL(fd_install); + +/* + * The same warnings as for __alloc_fd()/__fd_install() apply here... + */ +int __close_fd(struct files_struct *files, unsigned fd) +{ + struct file *file; + struct fdtable *fdt; + + spin_lock(&files->file_lock); + fdt = files_fdtable(files); + if (fd >= fdt->max_fds) + goto out_unlock; + file = fdt->fd[fd]; + if (!file) + goto out_unlock; + rcu_assign_pointer(fdt->fd[fd], NULL); + __clear_close_on_exec(fd, fdt); + __put_unused_fd(files, fd); + spin_unlock(&files->file_lock); + return filp_close(file, files); + +out_unlock: + spin_unlock(&files->file_lock); + return -EBADF; +} + +void do_close_on_exec(struct files_struct *files) +{ + unsigned i; + struct fdtable *fdt; + + /* exec unshares first */ + spin_lock(&files->file_lock); + for (i = 0; ; i++) { + unsigned long set; + unsigned fd = i * BITS_PER_LONG; + fdt = files_fdtable(files); + if (fd >= fdt->max_fds) + break; + set = fdt->close_on_exec[i]; + if (!set) + continue; + fdt->close_on_exec[i] = 0; + for ( ; set ; fd++, set >>= 1) { + struct file *file; + if (!(set & 1)) + continue; + file = fdt->fd[fd]; + if (!file) + continue; + rcu_assign_pointer(fdt->fd[fd], NULL); + __put_unused_fd(files, fd); + spin_unlock(&files->file_lock); + filp_close(file, files); + cond_resched(); + spin_lock(&files->file_lock); + } + + } + spin_unlock(&files->file_lock); +} + +static struct file *__fget(unsigned int fd, fmode_t mask) +{ + struct files_struct *files = current->files; + struct file *file; + + rcu_read_lock(); + file = fcheck_files(files, fd); + if (file) { + /* File object ref couldn't be taken */ + if ((file->f_mode & mask) || !get_file_rcu(file)) + file = NULL; + } + rcu_read_unlock(); + + return file; +} + +struct file *fget(unsigned int fd) +{ + return __fget(fd, FMODE_PATH); +} +EXPORT_SYMBOL(fget); + +struct file *fget_raw(unsigned int fd) +{ + return __fget(fd, 0); +} +EXPORT_SYMBOL(fget_raw); + +/* + * Lightweight file lookup - no refcnt increment if fd table isn't shared. + * + * You can use this instead of fget if you satisfy all of the following + * conditions: + * 1) You must call fput_light before exiting the syscall and returning control + * to userspace (i.e. you cannot remember the returned struct file * after + * returning to userspace). + * 2) You must not call filp_close on the returned struct file * in between + * calls to fget_light and fput_light. + * 3) You must not clone the current task in between the calls to fget_light + * and fput_light. + * + * The fput_needed flag returned by fget_light should be passed to the + * corresponding fput_light. + */ +static unsigned long __fget_light(unsigned int fd, fmode_t mask) +{ + struct files_struct *files = current->files; + struct file *file; + + if (atomic_read(&files->count) == 1) { + file = __fcheck_files(files, fd); + if (!file || unlikely(file->f_mode & mask)) + return 0; + return (unsigned long)file; + } else { + file = __fget(fd, mask); + if (!file) + return 0; + return FDPUT_FPUT | (unsigned long)file; + } +} +unsigned long __fdget(unsigned int fd) +{ + return __fget_light(fd, FMODE_PATH); +} +EXPORT_SYMBOL(__fdget); + +unsigned long __fdget_raw(unsigned int fd) +{ + return __fget_light(fd, 0); +} + +unsigned long __fdget_pos(unsigned int fd) +{ + unsigned long v = __fdget(fd); + struct file *file = (struct file *)(v & ~3); + + if (file && (file->f_mode & FMODE_ATOMIC_POS)) { + if (file_count(file) > 1) { + v |= FDPUT_POS_UNLOCK; + mutex_lock(&file->f_pos_lock); + } + } + return v; +} + +/* + * We only lock f_pos if we have threads or if the file might be + * shared with another process. In both cases we'll have an elevated + * file count (done either by fdget() or by fork()). + */ + +void set_close_on_exec(unsigned int fd, int flag) +{ + struct files_struct *files = current->files; + struct fdtable *fdt; + spin_lock(&files->file_lock); + fdt = files_fdtable(files); + if (flag) + __set_close_on_exec(fd, fdt); + else + __clear_close_on_exec(fd, fdt); + spin_unlock(&files->file_lock); +} + +bool get_close_on_exec(unsigned int fd) +{ + struct files_struct *files = current->files; + struct fdtable *fdt; + bool res; + rcu_read_lock(); + fdt = files_fdtable(files); + res = close_on_exec(fd, fdt); + rcu_read_unlock(); + return res; +} + +static int do_dup2(struct files_struct *files, + struct file *file, unsigned fd, unsigned flags) +__releases(&files->file_lock) +{ + struct file *tofree; + struct fdtable *fdt; + + /* + * We need to detect attempts to do dup2() over allocated but still + * not finished descriptor. NB: OpenBSD avoids that at the price of + * extra work in their equivalent of fget() - they insert struct + * file immediately after grabbing descriptor, mark it larval if + * more work (e.g. actual opening) is needed and make sure that + * fget() treats larval files as absent. Potentially interesting, + * but while extra work in fget() is trivial, locking implications + * and amount of surgery on open()-related paths in VFS are not. + * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" + * deadlocks in rather amusing ways, AFAICS. All of that is out of + * scope of POSIX or SUS, since neither considers shared descriptor + * tables and this condition does not arise without those. + */ + fdt = files_fdtable(files); + tofree = fdt->fd[fd]; + if (!tofree && fd_is_open(fd, fdt)) + goto Ebusy; + get_file(file); + rcu_assign_pointer(fdt->fd[fd], file); + __set_open_fd(fd, fdt); + if (flags & O_CLOEXEC) + __set_close_on_exec(fd, fdt); + else + __clear_close_on_exec(fd, fdt); + spin_unlock(&files->file_lock); + + if (tofree) + filp_close(tofree, files); + + return fd; + +Ebusy: + spin_unlock(&files->file_lock); + return -EBUSY; +} + +int replace_fd(unsigned fd, struct file *file, unsigned flags) +{ + int err; + struct files_struct *files = current->files; + + if (!file) + return __close_fd(files, fd); + + if (fd >= rlimit(RLIMIT_NOFILE)) + return -EBADF; + + spin_lock(&files->file_lock); + err = expand_files(files, fd); + if (unlikely(err < 0)) + goto out_unlock; + return do_dup2(files, file, fd, flags); + +out_unlock: + spin_unlock(&files->file_lock); + return err; +} + +SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) +{ + int err = -EBADF; + struct file *file; + struct files_struct *files = current->files; + + if ((flags & ~O_CLOEXEC) != 0) + return -EINVAL; + + if (unlikely(oldfd == newfd)) + return -EINVAL; + + if (newfd >= rlimit(RLIMIT_NOFILE)) + return -EBADF; + + spin_lock(&files->file_lock); + err = expand_files(files, newfd); + file = fcheck(oldfd); + if (unlikely(!file)) + goto Ebadf; + if (unlikely(err < 0)) { + if (err == -EMFILE) + goto Ebadf; + goto out_unlock; + } + return do_dup2(files, file, newfd, flags); + +Ebadf: + err = -EBADF; +out_unlock: + spin_unlock(&files->file_lock); + return err; +} + +SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) +{ + if (unlikely(newfd == oldfd)) { /* corner case */ + struct files_struct *files = current->files; + int retval = oldfd; + + rcu_read_lock(); + if (!fcheck_files(files, oldfd)) + retval = -EBADF; + rcu_read_unlock(); + return retval; + } + return sys_dup3(oldfd, newfd, 0); +} + +SYSCALL_DEFINE1(dup, unsigned int, fildes) +{ + int ret = -EBADF; + struct file *file = fget_raw(fildes); + + if (file) { + ret = get_unused_fd_flags(0); + if (ret >= 0) + fd_install(ret, file); + else + fput(file); + } + return ret; +} + +int f_dupfd(unsigned int from, struct file *file, unsigned flags) +{ + int err; + if (from >= rlimit(RLIMIT_NOFILE)) + return -EINVAL; + err = alloc_fd(from, flags); + if (err >= 0) { + get_file(file); + fd_install(err, file); + } + return err; +} + +int iterate_fd(struct files_struct *files, unsigned n, + int (*f)(const void *, struct file *, unsigned), + const void *p) +{ + struct fdtable *fdt; + int res = 0; + if (!files) + return 0; + spin_lock(&files->file_lock); + for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { + struct file *file; + file = rcu_dereference_check_fdtable(files, fdt->fd[n]); + if (!file) + continue; + res = f(p, file, n); + if (res) + break; + } + spin_unlock(&files->file_lock); + return res; +} +EXPORT_SYMBOL(iterate_fd); |