[PATCH AUTOSEL 5.4 15/16] gfs2: read-only mounts should grab the sd_freeze_gl glock

Sasha Levin
2020-07-08T15:42:03Z

From: Bob Peterson <rpeterso@redhat.com>

[ Upstream commit b780cc615ba4795a7ef0e93b19424828a5ad456a ]

Before this patch, only read-write mounts would grab the freeze
glock in read-only mode, as part of gfs2_make_fs_rw. So the freeze
glock was never initialized. That meant requests to freeze, which
request the glock in EX, were granted without any state transition.
That meant you could mount a gfs2 file system, which is currently
frozen on a different cluster node, in read-only mode.

This patch makes read-only mounts lock the freeze glock in SH mode,
which will block for file systems that are frozen on another node.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/gfs2/ops_fstype.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index c26c864590cc3..e0c55765b06d2 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1168,7 +1168,17 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
goto fail_per_node;
}

- if (!sb_rdonly(sb)) {
+ if (sb_rdonly(sb)) {
+ struct gfs2_holder freeze_gh;
+
+ error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED,
+ GL_EXACT, &freeze_gh);
+ if (error) {
+ fs_err(sdp, "can't make FS RO: %d\n", error);
+ goto fail_per_node;
+ }
+ gfs2_glock_dq_uninit(&freeze_gh);
+ } else {
error = gfs2_make_fs_rw(sdp);
if (error) {
fs_err(sdp, "can't make FS RW: %d\n", error);
--
2.25.1