summaryrefslogtreecommitdiff
path: root/fs
diff options
context:
space:
mode:
authorAndreas Gruenbacher <agruenba@redhat.com>2023-08-30 23:09:36 +0300
committerAndreas Gruenbacher <agruenba@redhat.com>2023-09-05 16:58:17 +0300
commite3da6be3d70449a1f14c99f13cc1eb453a2be4ea (patch)
tree8fd68f3768e75c0f0c48f29602bfefd76647e2fd /fs
parentfe0690f0a6f190a9ec0736c01ddeba7a729cf30d (diff)
downloadlinux-e3da6be3d70449a1f14c99f13cc1eb453a2be4ea.tar.xz
gfs2: Fix withdraw race
Function gfs2_withdraw() tries to synchronize concurrent callers by atomically setting the SDF_WITHDRAWN flag in the first caller, setting the SDF_WITHDRAW_IN_PROG flag to indicate that a withdraw is in progress, performing the actual withdraw, and clearing the SDF_WITHDRAW_IN_PROG flag when done. All other callers wait for the SDF_WITHDRAW_IN_PROG flag to be cleared before returning. This leaves a small window in which callers can find the SDF_WITHDRAWN flag set before the SDF_WITHDRAW_IN_PROG flag has been set, causing them to return prematurely, before the withdraw has been completed. Fix that by setting the SDF_WITHDRAWN and SDF_WITHDRAW_IN_PROG flags atomically. Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/gfs2/util.c24
1 files changed, 12 insertions, 12 deletions
diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
index 65a3c7b1a51e..da29fafb6272 100644
--- a/fs/gfs2/util.c
+++ b/fs/gfs2/util.c
@@ -323,19 +323,19 @@ int gfs2_withdraw(struct gfs2_sbd *sdp)
struct lm_lockstruct *ls = &sdp->sd_lockstruct;
const struct lm_lockops *lm = ls->ls_ops;
- if (sdp->sd_args.ar_errors == GFS2_ERRORS_WITHDRAW &&
- test_and_set_bit(SDF_WITHDRAWN, &sdp->sd_flags)) {
- if (!test_bit(SDF_WITHDRAW_IN_PROG, &sdp->sd_flags))
- return -1;
-
- wait_on_bit(&sdp->sd_flags, SDF_WITHDRAW_IN_PROG,
- TASK_UNINTERRUPTIBLE);
- return -1;
- }
-
- set_bit(SDF_WITHDRAW_IN_PROG, &sdp->sd_flags);
-
if (sdp->sd_args.ar_errors == GFS2_ERRORS_WITHDRAW) {
+ unsigned long old = READ_ONCE(sdp->sd_flags), new;
+
+ do {
+ if (old & BIT(SDF_WITHDRAWN)) {
+ wait_on_bit(&sdp->sd_flags,
+ SDF_WITHDRAW_IN_PROG,
+ TASK_UNINTERRUPTIBLE);
+ return -1;
+ }
+ new = old | BIT(SDF_WITHDRAWN) | BIT(SDF_WITHDRAW_IN_PROG);
+ } while (unlikely(!try_cmpxchg(&sdp->sd_flags, &old, new)));
+
fs_err(sdp, "about to withdraw this file system\n");
BUG_ON(sdp->sd_args.ar_debug);