[Cluster-devel] [GFS2 PATCH] gfs2: Don't freeze the file system during unmount

[Bob Peterson]

Hi,

GFS2's freeze/thaw mechanism uses a special freeze glock to control its
operation. It does this with a sync glock operation (glops.c) called
freeze_go_sync. When the freeze glock is demoted (glock's do_xmote) the
glops function causes the file system to be frozen. This is intended. However,
GFS2's mount and unmount processes also hold the freeze glock to prevent other
processes, perhaps on different cluster nodes, from mounting the frozen file
system in read-write mode.

Before this patch, there was no check in freeze_go_sync for whether a freeze
in intended or whether the glock demote was caused by a normal unmount.
So it was trying to freeze the file system it's trying to unmount, which
ends up in a deadlock.

This patch adds an additional check to freeze_go_sync so that demotes of the
freeze glock are ignored if they come from the unmount process.

Signed-off-by: Bob Peterson <rpeterso at redhat.com>
---
 fs/gfs2/glops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index e2cfc00ab936..3faa421568b0 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -582,7 +582,8 @@ static int freeze_go_sync(struct gfs2_glock *gl)
 	 * Once thawed, the work func acquires the freeze glock in
 	 * SH and everybody goes back to thawed.
 	 */
-	if (gl->gl_state == LM_ST_SHARED && !gfs2_withdrawn(sdp)) {
+	if (gl->gl_state == LM_ST_SHARED && !gfs2_withdrawn(sdp) &&
+	    !test_bit(SDF_NORECOVERY, &sdp->sd_flags)) {
 		atomic_set(&sdp->sd_freeze_state, SFS_STARTING_FREEZE);
 		error = freeze_super(sdp->sd_vfs);
 		if (error) {