[PATCH AUTOSEL 5.6 264/606] gfs2: Grab glock reference sooner in gfs2_add_revoke

Sasha Levin
2020-06-09T00:22:23Z

From: Andreas Gruenbacher <agruenba@redhat.com>

[ Upstream commit f4e2f5e1a527ce58fc9f85145b03704779a3123e ]

This patch rearranges gfs2_add_revoke so that the extra glock
reference is added earlier on in the function to avoid races in which
the glock is freed before the new reference is taken.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/gfs2/log.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 60d911e293e6..2674feda1d7a 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -603,13 +603,13 @@ void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
struct buffer_head *bh = bd->bd_bh;
struct gfs2_glock *gl = bd->bd_gl;

+ sdp->sd_log_num_revoke++;
+ if (atomic_inc_return(&gl->gl_revokes) == 1)
+ gfs2_glock_hold(gl);
bh->b_private = NULL;
bd->bd_blkno = bh->b_blocknr;
gfs2_remove_from_ail(bd); /* drops ref on bh */
bd->bd_bh = NULL;
- sdp->sd_log_num_revoke++;
- if (atomic_inc_return(&gl->gl_revokes) == 1)
- gfs2_glock_hold(gl);
set_bit(GLF_LFLUSH, &gl->gl_flags);
list_add(&bd->bd_list, &sdp->sd_log_revokes);
}
--
2.25.1