diff options
| -rw-r--r-- | fs/notify/inotify/inotify.c | 32 | ||||
| -rw-r--r-- | fs/super.c | 28 | ||||
| -rw-r--r-- | include/linux/fs.h | 1 |
3 files changed, 24 insertions, 37 deletions
diff --git a/fs/notify/inotify/inotify.c b/fs/notify/inotify/inotify.c index 40b1cf914cc..441ef136af2 100644 --- a/fs/notify/inotify/inotify.c +++ b/fs/notify/inotify/inotify.c @@ -110,14 +110,10 @@ EXPORT_SYMBOL_GPL(get_inotify_watch); int pin_inotify_watch(struct inotify_watch *watch) { struct super_block *sb = watch->inode->i_sb; - spin_lock(&sb_lock); - if (sb->s_count >= S_BIAS) { - atomic_inc(&sb->s_active); - spin_unlock(&sb_lock); + if (atomic_inc_not_zero(&sb->s_active)) { atomic_inc(&watch->count); return 1; } - spin_unlock(&sb_lock); return 0; } @@ -518,16 +514,16 @@ EXPORT_SYMBOL_GPL(inotify_init_watch); * ->s_umount, which will almost certainly wait until the superblock is shut * down and the watch in question is pining for fjords. That's fine, but * there is a problem - we might have hit the window between ->s_active - * getting to 0 / ->s_count - below S_BIAS (i.e. the moment when superblock - * is past the point of no return and is heading for shutdown) and the - * moment when deactivate_super() acquires ->s_umount. We could just do - * drop_super() yield() and retry, but that's rather antisocial and this - * stuff is luser-triggerable. OTOH, having grabbed ->s_umount and having - * found that we'd got there first (i.e. that ->s_root is non-NULL) we know - * that we won't race with inotify_umount_inodes(). So we could grab a - * reference to watch and do the rest as above, just with drop_super() instead - * of deactivate_super(), right? Wrong. We had to drop ih->mutex before we - * could grab ->s_umount. So the watch could've been gone already. + * getting to 0 (i.e. the moment when superblock is past the point of no return + * and is heading for shutdown) and the moment when deactivate_super() acquires + * ->s_umount. We could just do drop_super() yield() and retry, but that's + * rather antisocial and this stuff is luser-triggerable. OTOH, having grabbed + * ->s_umount and having found that we'd got there first (i.e. that ->s_root is + * non-NULL) we know that we won't race with inotify_umount_inodes(). So we + * could grab a reference to watch and do the rest as above, just with + * drop_super() instead of deactivate_super(), right? Wrong. We had to drop + * ih->mutex before we could grab ->s_umount. So the watch could've been gone + * already. * * That still can be dealt with - we need to save watch->wd, do idr_find() * and compare its result with our pointer. If they match, we either have @@ -565,14 +561,12 @@ static int pin_to_kill(struct inotify_handle *ih, struct inotify_watch *watch) struct super_block *sb = watch->inode->i_sb; s32 wd = watch->wd; - spin_lock(&sb_lock); - if (sb->s_count >= S_BIAS) { - atomic_inc(&sb->s_active); - spin_unlock(&sb_lock); + if (atomic_inc_not_zero(&sb->s_active)) { get_inotify_watch(watch); mutex_unlock(&ih->mutex); return 1; /* the best outcome */ } + spin_lock(&sb_lock); sb->s_count++; spin_unlock(&sb_lock); mutex_unlock(&ih->mutex); /* can't grab ->s_umount under it */ diff --git a/fs/super.c b/fs/super.c index d8c8b1d2d01..bc734f8b3e1 100644 --- a/fs/super.c +++ b/fs/super.c @@ -93,7 +93,7 @@ static struct super_block *alloc_super(struct file_system_type *type) * subclass. */ down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); - s->s_count = S_BIAS; + s->s_count = 1; atomic_set(&s->s_active, 1); mutex_init(&s->s_vfs_rename_mutex); mutex_init(&s->s_dquot.dqio_mutex); @@ -189,9 +189,7 @@ void put_super(struct super_block *sb) void deactivate_super(struct super_block *s) { struct file_system_type *fs = s->s_type; - if (atomic_dec_and_lock(&s->s_active, &sb_lock)) { - s->s_count -= S_BIAS-1; - spin_unlock(&sb_lock); + if (atomic_dec_and_test(&s->s_active)) { vfs_dq_off(s, 0); down_write(&s->s_umount); fs->kill_sb(s); @@ -216,9 +214,7 @@ EXPORT_SYMBOL(deactivate_super); void deactivate_locked_super(struct super_block *s) { struct file_system_type *fs = s->s_type; - if (atomic_dec_and_lock(&s->s_active, &sb_lock)) { - s->s_count -= S_BIAS-1; - spin_unlock(&sb_lock); + if (atomic_dec_and_test(&s->s_active)) { vfs_dq_off(s, 0); fs->kill_sb(s); put_filesystem(fs); @@ -243,21 +239,19 @@ EXPORT_SYMBOL(deactivate_locked_super); */ static int grab_super(struct super_block *s) __releases(sb_lock) { + if (atomic_inc_not_zero(&s->s_active)) { + spin_unlock(&sb_lock); + down_write(&s->s_umount); + return 1; + } + /* it's going away */ s->s_count++; spin_unlock(&sb_lock); + /* usually that'll be enough for it to die... */ down_write(&s->s_umount); - if (s->s_root) { - spin_lock(&sb_lock); - if (s->s_count > S_BIAS) { - atomic_inc(&s->s_active); - s->s_count--; - spin_unlock(&sb_lock); - return 1; - } - spin_unlock(&sb_lock); - } up_write(&s->s_umount); put_super(s); + /* ... but in case it wasn't, let's at least yield() */ yield(); return 0; } diff --git a/include/linux/fs.h b/include/linux/fs.h index d13a6b83ad0..62f84d955b8 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1314,7 +1314,6 @@ extern int send_sigurg(struct fown_struct *fown); extern struct list_head super_blocks; extern spinlock_t sb_lock; -#define S_BIAS (1<<30) struct super_block { struct list_head s_list; /* Keep this first */ dev_t s_dev; /* search index; _not_ kdev_t */ |