[PATCH 14/49] ext4: Replace lock/unlock_super() with an explicit lock for the orphan list

Theodore Ts'o
2009-06-08T19:33:58Z

Use a separate lock to protect the orphan list, so we can stop
overloading the use of lock_super().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/ext4_sb.h | 1 +
fs/ext4/namei.c | 20 +++++++++++---------
fs/ext4/super.c | 1 +
3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h
index 57b71fe..4bda2f7 100644
--- a/fs/ext4/ext4_sb.h
+++ b/fs/ext4/ext4_sb.h
@@ -71,6 +71,7 @@ struct ext4_sb_info {
struct inode *s_journal_inode;
struct journal_s *s_journal;
struct list_head s_orphan;
+ struct mutex s_orphan_lock;
unsigned long s_commit_interval;
u32 s_max_batch_time;
u32 s_min_batch_time;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 22098e1..8018e49 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1997,7 +1997,7 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
if (!ext4_handle_valid(handle))
return 0;

- lock_super(sb);
+ mutex_lock(&EXT4_SB(sb)->s_orphan_lock);
if (!list_empty(&EXT4_I(inode)->i_orphan))
goto out_unlock;

@@ -2006,9 +2006,13 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)

/* @@@ FIXME: Observation from aviro:
* I think I can trigger J_ASSERT in ext4_orphan_add(). We block
- * here (on lock_super()), so race with ext4_link() which might bump
+ * here (on s_orphan_lock), so race with ext4_link() which might bump
* ->i_nlink. For, say it, character device. Not a regular file,
* not a directory, not a symlink and ->i_nlink > 0.
+ *
+ * tytso, 4/25/2009: I'm not sure how that could happen;
+ * shouldn't the fs core protect us from these sort of
+ * unlink()/link() races?
*/
J_ASSERT((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
S_ISLNK(inode->i_mode)) || inode->i_nlink == 0);
@@ -2045,7 +2049,7 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
jbd_debug(4, "orphan inode %lu will point to %d\n",
inode->i_ino, NEXT_ORPHAN(inode));
out_unlock:
- unlock_super(sb);
+ mutex_unlock(&EXT4_SB(sb)->s_orphan_lock);
ext4_std_error(inode->i_sb, err);
return err;
}
@@ -2066,11 +2070,9 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
if (!ext4_handle_valid(handle))
return 0;

- lock_super(inode->i_sb);
- if (list_empty(&ei->i_orphan)) {
- unlock_super(inode->i_sb);
- return 0;
- }
+ mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
+ if (list_empty(&ei->i_orphan))
+ goto out;

ino_next = NEXT_ORPHAN(inode);
prev = ei->i_orphan.prev;
@@ -2120,7 +2122,7 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
out_err:
ext4_std_error(inode->i_sb, err);
out:
- unlock_super(inode->i_sb);
+ mutex_unlock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
return err;

out_brelse:
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 45d0ada..7f43fde 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2645,6 +2645,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sb->dq_op = &ext4_quota_operations;
#endif
INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
+ mutex_init(&sbi->s_orphan_lock);

sb->s_root = NULL;

--
1.6.3.2.1.gb9f7d.dirty