writeback: Fix lock imbalance in writeback_sb_inodes()
Fix bug introduced by 169ebd90. We have to have wb_list_lock locked when
restarting writeback loop after having waited for inode writeback.
Bug description by Ted Tso:
I can reproduce this fairly easily by using ext4 w/o a journal, running
under KVM with 1024megs memory, with fsstress (xfstests #13):
[ 45.153294] =====================================
[ 45.154784] [ BUG: bad unlock balance detected! ]
[ 45.155591] 3.5.0-rc1-00002-gb22b1f1 #124 Not tainted
[ 45.155591] -------------------------------------
[ 45.155591] flush-254:16/2499 is trying to release lock (&(&wb->list_lock)->rlock) at:
[ 45.155591] [<c022c3da>] writeback_sb_inodes+0x160/0x327
[ 45.155591] but there are no more locks to release!
Reported-by: Theodore Ts'o <tytso@mit.edu>
Tested-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8d2fb8c..41a3ccf 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -664,6 +664,7 @@
/* Wait for I_SYNC. This function drops i_lock... */
inode_sleep_on_writeback(inode);
/* Inode may be gone, start again */
+ spin_lock(&wb->list_lock);
continue;
}
inode->i_state |= I_SYNC;