diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/fs-writeback.c | 6 | ||||
| -rw-r--r-- | fs/internal.h | 2 | ||||
| -rw-r--r-- | fs/super.c | 40 |
3 files changed, 22 insertions, 26 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 073657f755d4..e907052eeadb 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -769,9 +769,9 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb, struct inode *inode = wb_inode(wb->b_io.prev); struct super_block *sb = inode->i_sb; - if (!grab_super_passive(sb)) { + if (!trylock_super(sb)) { /* - * grab_super_passive() may fail consistently due to + * trylock_super() may fail consistently due to * s_umount being grabbed by someone else. Don't use * requeue_io() to avoid busy retrying the inode/sb. */ @@ -779,7 +779,7 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb, continue; } wrote += writeback_sb_inodes(sb, wb, work); - drop_super(sb); + up_read(&sb->s_umount); /* refer to the same tests at the end of writeback_sb_inodes */ if (wrote) { diff --git a/fs/internal.h b/fs/internal.h index 30459dab409d..01dce1d1476b 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -84,7 +84,7 @@ extern struct file *get_empty_filp(void); * super.c */ extern int do_remount_sb(struct super_block *, int, void *, int); -extern bool grab_super_passive(struct super_block *sb); +extern bool trylock_super(struct super_block *sb); extern struct dentry *mount_fs(struct file_system_type *, int, const char *, void *); extern struct super_block *user_get_super(dev_t); diff --git a/fs/super.c b/fs/super.c index 65a53efc1cf4..2b7dc90ccdbb 100644 --- a/fs/super.c +++ b/fs/super.c @@ -71,7 +71,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, if (!(sc->gfp_mask & __GFP_FS)) return SHRINK_STOP; - if (!grab_super_passive(sb)) + if (!trylock_super(sb)) return SHRINK_STOP; if (sb->s_op->nr_cached_objects) @@ -105,7 +105,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, freed += sb->s_op->free_cached_objects(sb, sc); } - drop_super(sb); + up_read(&sb->s_umount); return freed; } @@ -118,7 +118,7 @@ static unsigned long super_cache_count(struct shrinker *shrink, sb = container_of(shrink, struct super_block, s_shrink); /* - * Don't call grab_super_passive as it is a potential + * Don't call trylock_super as it is a potential * scalability bottleneck. The counts could get updated * between super_cache_count and super_cache_scan anyway. * Call to super_cache_count with shrinker_rwsem held @@ -348,35 +348,31 @@ static int grab_super(struct super_block *s) __releases(sb_lock) } /* - * grab_super_passive - acquire a passive reference + * trylock_super - try to grab ->s_umount shared * @sb: reference we are trying to grab * - * Tries to acquire a passive reference. This is used in places where we + * Try to prevent fs shutdown. This is used in places where we * cannot take an active reference but we need to ensure that the - * superblock does not go away while we are working on it. It returns - * false if a reference was not gained, and returns true with the s_umount - * lock held in read mode if a reference is gained. On successful return, - * the caller must drop the s_umount lock and the passive reference when - * done. + * filesystem is not shut down while we are working on it. It returns + * false if we cannot acquire s_umount or if we lose the race and + * filesystem already got into shutdown, and returns true with the s_umount + * lock held in read mode in case of success. On successful return, + * the caller must drop the s_umount lock when done. + * + * Note that unlike get_super() et.al. this one does *not* bump ->s_count. + * The reason why it's safe is that we are OK with doing trylock instead + * of down_read(). There's a couple of places that are OK with that, but + * it's very much not a general-purpose interface. */ -bool grab_super_passive(struct super_block *sb) +bool trylock_super(struct super_block *sb) { - spin_lock(&sb_lock); - if (hlist_unhashed(&sb->s_instances)) { - spin_unlock(&sb_lock); - return false; - } - - sb->s_count++; - spin_unlock(&sb_lock); - if (down_read_trylock(&sb->s_umount)) { - if (sb->s_root && (sb->s_flags & MS_BORN)) + if (!hlist_unhashed(&sb->s_instances) && + sb->s_root && (sb->s_flags & MS_BORN)) return true; up_read(&sb->s_umount); } - put_super(sb); return false; } |