[Cluster-devel] [PATCH 1/3] gfs2: Prevent double iput for journal on error

[Bob Peterson <rpeterso@redhat.com>]

When a gfs2 file system is withdrawn, it requests recovery from another
cluster node. To do that, it evicts its journal from memory, but it
keeps the journal entry queued to the journals queue, jindex_list. After
recovery it tries to grab a new inode for its (recovered) journal. If it
cannot, it skips further recovery but its evicted journal is still on
the jindex list, which means unmount will try to iput it a second time
after it's been evicted. This second iput causes vfs to complain and BUG
out:

kernel BUG at fs/inode.c:1680!

To prevent this, this patch takes steps to dequeue the journal
descriptor from the list when it cannot get a replacement inode. So
unmount won't find it on the list and try to iput it again.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
 fs/gfs2/util.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
index 8241029a2a5d..78cb12d0fba1 100644
--- a/fs/gfs2/util.c
+++ b/fs/gfs2/util.c
@@ -275,6 +275,17 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp)
 	if (IS_ERR(inode)) {
 		fs_warn(sdp, "Reprocessing of jid %d failed with %ld.\n",
 			sdp->sd_lockstruct.ls_jid, PTR_ERR(inode));
+		/*
+		 * We couldn't get a replacement inode for our journal but we
+		 * evicted the old one. So dequeue it from the journals queue,
+		 * jindex_list, so that unmount doesn't do iput on it twice.
+		 */
+		spin_lock(&sdp->sd_jindex_spin);
+		list_del(&sdp->sd_jdesc->jd_list);
+		sdp->sd_journals--;
+		spin_unlock(&sdp->sd_jindex_spin);
+		kfree(sdp->sd_jdesc);
+		sdp->sd_jdesc = NULL;
 		goto skip_recovery;
 	}
 	sdp->sd_jdesc->jd_inode = inode;
-- 
2.36.1