reiserfs: fix deadlocks with quotas

The BKL push-down for reiserfs made lock recursion a special case that needs
to be handled explicitly. One of the cases that was unhandled is dropping
the quota during inode eviction. Both reiserfs_evict_inode and
reiserfs_write_dquot take the write lock, but when the journal lock is
taken it only drops one the references. The locking rules are that the journal
lock be acquired before the write lock so leaving the reference open leads
to a ABBA deadlock.

This patch pushes the unlock up before clear_inode and avoids the recursive
locking.

Another ABBA situation can occur when the write lock is dropped while reading
the bitmap buffer while in the quota code. When the lock is reacquired, it
will deadlock against dquot->dq_lock and dqopt->dqio_mutex in the dquot_acquire
path. It's safe to retain the lock across the read and should be cached under
write load.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/reiserfs/bitmap.c b/fs/reiserfs/bitmap.c
index 4c0c7d163d150c02535cffcad08a1aead02f53d2..a98b7740a0fcade0b894920154e65ecbe7987509 100644 (file)
--- a/fs/reiserfs/bitmap.c
+++ b/fs/reiserfs/bitmap.c
@@ -1334,9 +1334,7 @@ struct buffer_head *reiserfs_read_bitmap_block(struct super_block *sb,
        else if (bitmap == 0)
                block = (REISERFS_DISK_OFFSET_IN_BYTES >> sb->s_blocksize_bits) + 1;
 
-       reiserfs_write_unlock(sb);
        bh = sb_bread(sb, block);
-       reiserfs_write_lock(sb);
        if (bh == NULL)
                reiserfs_warning(sb, "sh-2029: %s: bitmap block (#%u) "
                                 "reading failed", __func__, block);

diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index a6d4268fb6c11798db5f8339bd14ab297cd9b21f..855da58db1456b94d43715bb4a28bbc5f982a8d7 100644 (file)
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -76,10 +76,10 @@ void reiserfs_evict_inode(struct inode *inode)
                ;
        }
       out:
+       reiserfs_write_unlock_once(inode->i_sb, depth);
        clear_inode(inode);     /* note this must go after the journal_end to prevent deadlock */
        dquot_drop(inode);
        inode->i_blocks = 0;
-       reiserfs_write_unlock_once(inode->i_sb, depth);
        return;
 
 no_delete: