Re: [Bug 18632] "INFO: task" dpkg "blocked for more than 120 seconds.

[Christoph Hellwig <hch@infradead.org>]

Here is a patch that removes the XFS-internal writing of data in sync
and instead trusts the VFS code to get it right, and also does the
ioend_wait under a lock, to protect against new pending I/Os showing up.

It passed a single xfsqa run so far, so at least it won't blow up
completely.

Can you check if that helps with your livelock test case?  (And yes, I
should go and try it myself.  Will do as soon as I'll get a bit more
time).


Index: xfs/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_super.c	2011-06-09 14:17:06.952532698 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_super.c	2011-06-09 14:17:36.742531190 +0200
@@ -991,7 +991,7 @@ xfs_fs_write_inode(
 		 * ->sync_fs call do that for thus, which reduces the number
 		 * of synchronous log foces dramatically.
 		 */
-		xfs_ioend_wait(ip);
+//		xfs_ioend_wait(ip);
 		xfs_ilock(ip, XFS_ILOCK_SHARED);
 		if (ip->i_update_core) {
 			error = xfs_log_inode(ip);
Index: xfs/fs/xfs/linux-2.6/xfs_sync.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_sync.c	2011-06-09 14:16:59.575866405 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_sync.c	2011-06-09 14:22:31.675849591 +0200
@@ -215,6 +215,19 @@ xfs_inode_ag_iterator(
 }
 
 STATIC int
+xfs_wait_ioend_cb(
+	struct xfs_inode	*ip,
+	struct xfs_perag	*pag,
+	int			flags)
+{
+	xfs_ilock(ip, XFS_IOLOCK_SHARED);
+	xfs_ioend_wait(ip);
+	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+
+	return 0;
+}
+
+STATIC int
 xfs_sync_inode_data(
 	struct xfs_inode	*ip,
 	struct xfs_perag	*pag,
@@ -359,14 +372,14 @@ xfs_quiesce_data(
 {
 	int			error, error2 = 0;
 
-	/* push non-blocking */
-	xfs_sync_data(mp, 0);
-	xfs_qm_sync(mp, SYNC_TRYLOCK);
-
-	/* push and block till complete */
-	xfs_sync_data(mp, SYNC_WAIT);
 	xfs_qm_sync(mp, SYNC_WAIT);
 
+	error = xfs_inode_ag_iterator(mp, xfs_wait_ioend_cb, 0);
+	if (error)
+		return XFS_ERROR(error);
+
+	xfs_log_force(mp, XFS_LOG_SYNC);
+
 	/* write superblock and hoover up shutdown errors */
 	error = xfs_sync_fsdata(mp);