diff options
Diffstat (limited to 'fs/super.c')
| -rw-r--r-- | fs/super.c | 33 |
1 files changed, 33 insertions, 0 deletions
@@ -243,6 +243,39 @@ static int grab_super(struct super_block *s) __releases(sb_lock) } /* + * grab_super_passive - acquire a passive reference + * @s: reference we are trying to grab + * + * Tries to acquire a passive reference. 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. + */ +bool grab_super_passive(struct super_block *sb) +{ + spin_lock(&sb_lock); + if (list_empty(&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) + return true; + up_read(&sb->s_umount); + } + + put_super(sb); + return false; +} + +/* * Superblock locking. We really ought to get rid of these two. */ void lock_super(struct super_block * sb) |
