diff options
| -rw-r--r-- | fs/fcntl.c | 102 |
1 files changed, 66 insertions, 36 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c index 2cf93ec40a6..97e01dc0d95 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -618,60 +618,90 @@ static DEFINE_RWLOCK(fasync_lock); static struct kmem_cache *fasync_cache __read_mostly; /* - * fasync_helper() is used by almost all character device drivers - * to set up the fasync queue. It returns negative on error, 0 if it did - * no changes and positive if it added/deleted the entry. + * Remove a fasync entry. If successfully removed, return + * positive and clear the FASYNC flag. If no entry exists, + * do nothing and return 0. + * + * NOTE! It is very important that the FASYNC flag always + * match the state "is the filp on a fasync list". + * + * We always take the 'filp->f_lock', in since fasync_lock + * needs to be irq-safe. */ -int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp) +static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp) { struct fasync_struct *fa, **fp; - struct fasync_struct *new = NULL; int result = 0; - if (on) { - new = kmem_cache_alloc(fasync_cache, GFP_KERNEL); - if (!new) - return -ENOMEM; + spin_lock(&filp->f_lock); + write_lock_irq(&fasync_lock); + for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) { + if (fa->fa_file != filp) + continue; + *fp = fa->fa_next; + kmem_cache_free(fasync_cache, fa); + filp->f_flags &= ~FASYNC; + result = 1; + break; } + write_unlock_irq(&fasync_lock); + spin_unlock(&filp->f_lock); + return result; +} + +/* + * Add a fasync entry. Return negative on error, positive if + * added, and zero if did nothing but change an existing one. + * + * NOTE! It is very important that the FASYNC flag always + * match the state "is the filp on a fasync list". + */ +static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp) +{ + struct fasync_struct *new, *fa, **fp; + int result = 0; + + new = kmem_cache_alloc(fasync_cache, GFP_KERNEL); + if (!new) + return -ENOMEM; - /* - * We need to take f_lock first since it's not an IRQ-safe - * lock. - */ spin_lock(&filp->f_lock); write_lock_irq(&fasync_lock); for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) { - if (fa->fa_file == filp) { - if(on) { - fa->fa_fd = fd; - kmem_cache_free(fasync_cache, new); - } else { - *fp = fa->fa_next; - kmem_cache_free(fasync_cache, fa); - result = 1; - } - goto out; - } + if (fa->fa_file != filp) + continue; + fa->fa_fd = fd; + kmem_cache_free(fasync_cache, new); + goto out; } - if (on) { - new->magic = FASYNC_MAGIC; - new->fa_file = filp; - new->fa_fd = fd; - new->fa_next = *fapp; - *fapp = new; - result = 1; - } + new->magic = FASYNC_MAGIC; + new->fa_file = filp; + new->fa_fd = fd; + new->fa_next = *fapp; + *fapp = new; + result = 1; + filp->f_flags |= FASYNC; + out: - if (on) - filp->f_flags |= FASYNC; - else - filp->f_flags &= ~FASYNC; write_unlock_irq(&fasync_lock); spin_unlock(&filp->f_lock); return result; } +/* + * fasync_helper() is used by almost all character device drivers + * to set up the fasync queue, and for regular files by the file + * lease code. It returns negative on error, 0 if it did no changes + * and positive if it added/deleted the entry. + */ +int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp) +{ + if (!on) + return fasync_remove_entry(filp, fapp); + return fasync_add_entry(fd, filp, fapp); +} + EXPORT_SYMBOL(fasync_helper); void __kill_fasync(struct fasync_struct *fa, int sig, int band) |