diff options
Diffstat (limited to 'fs/file.c')
| -rw-r--r-- | fs/file.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/fs/file.c b/fs/file.c new file mode 100644 index 000000000000..92b5f25985d2 --- /dev/null +++ b/fs/file.c @@ -0,0 +1,254 @@ +/* + * 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> + + +/* + * Allocate an fd array, using kmalloc or vmalloc. + * Note: the array isn't cleared at allocation time. + */ +struct file ** alloc_fd_array(int num) +{ + struct file **new_fds; + int size = num * sizeof(struct file *); + + if (size <= PAGE_SIZE) + new_fds = (struct file **) kmalloc(size, GFP_KERNEL); + else + new_fds = (struct file **) vmalloc(size); + return new_fds; +} + +void free_fd_array(struct file **array, int num) +{ + int size = num * sizeof(struct file *); + + if (!array) { + printk (KERN_ERR "free_fd_array: array = 0 (num = %d)\n", num); + return; + } + + if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */ + return; + else if (size <= PAGE_SIZE) + kfree(array); + else + vfree(array); +} + +/* + * Expand the fd array in the files_struct. Called with the files + * spinlock held for write. + */ + +static int expand_fd_array(struct files_struct *files, int nr) + __releases(files->file_lock) + __acquires(files->file_lock) +{ + struct file **new_fds; + int error, nfds; + + + error = -EMFILE; + if (files->max_fds >= NR_OPEN || nr >= NR_OPEN) + goto out; + + nfds = files->max_fds; + spin_unlock(&files->file_lock); + + /* + * Expand to the max in easy steps, and keep expanding it until + * we have enough for the requested fd array size. + */ + + do { +#if NR_OPEN_DEFAULT < 256 + if (nfds < 256) + nfds = 256; + else +#endif + if (nfds < (PAGE_SIZE / sizeof(struct file *))) + nfds = PAGE_SIZE / sizeof(struct file *); + else { + nfds = nfds * 2; + if (nfds > NR_OPEN) + nfds = NR_OPEN; + } + } while (nfds <= nr); + + error = -ENOMEM; + new_fds = alloc_fd_array(nfds); + spin_lock(&files->file_lock); + if (!new_fds) + goto out; + + /* Copy the existing array and install the new pointer */ + + if (nfds > files->max_fds) { + struct file **old_fds; + int i; + + old_fds = xchg(&files->fd, new_fds); + i = xchg(&files->max_fds, nfds); + + /* Don't copy/clear the array if we are creating a new + fd array for fork() */ + if (i) { + memcpy(new_fds, old_fds, i * sizeof(struct file *)); + /* clear the remainder of the array */ + memset(&new_fds[i], 0, + (nfds-i) * sizeof(struct file *)); + + spin_unlock(&files->file_lock); + free_fd_array(old_fds, i); + spin_lock(&files->file_lock); + } + } else { + /* Somebody expanded the array while we slept ... */ + spin_unlock(&files->file_lock); + free_fd_array(new_fds, nfds); + spin_lock(&files->file_lock); + } + error = 0; +out: + return error; +} + +/* + * Allocate an fdset array, using kmalloc or vmalloc. + * Note: the array isn't cleared at allocation time. + */ +fd_set * alloc_fdset(int num) +{ + fd_set *new_fdset; + int size = num / 8; + + if (size <= PAGE_SIZE) + new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL); + else + new_fdset = (fd_set *) vmalloc(size); + return new_fdset; +} + +void free_fdset(fd_set *array, int num) +{ + int size = num / 8; + + if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */ + return; + else if (size <= PAGE_SIZE) + kfree(array); + else + vfree(array); +} + +/* + * Expand the fdset in the files_struct. Called with the files spinlock + * held for write. + */ +static int expand_fdset(struct files_struct *files, int nr) + __releases(file->file_lock) + __acquires(file->file_lock) +{ + fd_set *new_openset = NULL, *new_execset = NULL; + int error, nfds = 0; + + error = -EMFILE; + if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN) + goto out; + + nfds = files->max_fdset; + spin_unlock(&files->file_lock); + + /* Expand to the max in easy steps */ + do { + if (nfds < (PAGE_SIZE * 8)) + nfds = PAGE_SIZE * 8; + else { + nfds = nfds * 2; + if (nfds > NR_OPEN) + nfds = NR_OPEN; + } + } while (nfds <= nr); + + error = -ENOMEM; + new_openset = alloc_fdset(nfds); + new_execset = alloc_fdset(nfds); + spin_lock(&files->file_lock); + if (!new_openset || !new_execset) + goto out; + + error = 0; + + /* Copy the existing tables and install the new pointers */ + if (nfds > files->max_fdset) { + int i = files->max_fdset / (sizeof(unsigned long) * 8); + int count = (nfds - files->max_fdset) / 8; + + /* + * Don't copy the entire array if the current fdset is + * not yet initialised. + */ + if (i) { + memcpy (new_openset, files->open_fds, files->max_fdset/8); + memcpy (new_execset, files->close_on_exec, files->max_fdset/8); + memset (&new_openset->fds_bits[i], 0, count); + memset (&new_execset->fds_bits[i], 0, count); + } + + nfds = xchg(&files->max_fdset, nfds); + new_openset = xchg(&files->open_fds, new_openset); + new_execset = xchg(&files->close_on_exec, new_execset); + spin_unlock(&files->file_lock); + free_fdset (new_openset, nfds); + free_fdset (new_execset, nfds); + spin_lock(&files->file_lock); + return 0; + } + /* Somebody expanded the array while we slept ... */ + +out: + spin_unlock(&files->file_lock); + if (new_openset) + free_fdset(new_openset, nfds); + if (new_execset) + free_fdset(new_execset, nfds); + spin_lock(&files->file_lock); + return error; +} + +/* + * Expand files. + * Return <0 on error; 0 nothing done; 1 files expanded, we may have blocked. + * Should be called with the files->file_lock spinlock held for write. + */ +int expand_files(struct files_struct *files, int nr) +{ + int err, expand = 0; + + if (nr >= files->max_fdset) { + expand = 1; + if ((err = expand_fdset(files, nr))) + goto out; + } + if (nr >= files->max_fds) { + expand = 1; + if ((err = expand_fd_array(files, nr))) + goto out; + } + err = expand; +out: + return err; +} |