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| author | Andreas Gruenbacher <agruenba@redhat.com> | 2023-08-30 22:09:36 +0200 |
|---|---|---|
| committer | Andreas Gruenbacher <agruenba@redhat.com> | 2023-09-05 15:58:17 +0200 |
| commit | e3da6be3d70449a1f14c99f13cc1eb453a2be4ea (patch) | |
| tree | 8fd68f3768e75c0f0c48f29602bfefd76647e2fd | |
| parent | fe0690f0a6f190a9ec0736c01ddeba7a729cf30d (diff) | |
| download | linux-e3da6be3d70449a1f14c99f13cc1eb453a2be4ea.tar.gz | |
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>
| -rw-r--r-- | fs/gfs2/util.c | 24 |
1 files changed, 12 insertions, 12 deletions
diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c index 65a3c7b1a51e93..da29fafb62728a 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); |