ext4: Replace lock/unlock_super() with an explicit lock for the orphan list

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>

3 files changed, 13 insertions, 9 deletions

diff --git a/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h
index 57b71fefbccf..4bda2f75d426 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 22098e1cd085..8018e49a7287 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 45d0ada9bfce..7f43fde9554b 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;