diff options
author | Alexander Aring <aahringo@redhat.com> | 2022-04-29 18:06:51 +0300 |
---|---|---|
committer | David Teigland <teigland@redhat.com> | 2022-05-02 19:15:59 +0300 |
commit | 1689c169134f4b5a39156122d799b7dca76d8ddb (patch) | |
tree | 2ae47cfaebf7accc7206d78bcc6985eb067fa624 /fs/dlm/lock.c | |
parent | e425ac99b1573692fc4bb5bda1040caccb127490 (diff) | |
download | linux-1689c169134f4b5a39156122d799b7dca76d8ddb.tar.xz |
dlm: fix missing lkb refcount handling
We always call hold_lkb(lkb) if we increment lkb->lkb_wait_count.
So, we always need to call unhold_lkb(lkb) if we decrement
lkb->lkb_wait_count. This patch will add missing unhold_lkb(lkb) if we
decrement lkb->lkb_wait_count. In case of setting lkb->lkb_wait_count to
zero we need to countdown until reaching zero and call unhold_lkb(lkb).
The waiters list unhold_lkb(lkb) can be removed because it's done for
the last lkb_wait_count decrement iteration as it's done in
_remove_from_waiters().
This issue was discovered by a dlm gfs2 test case which use excessively
dlm_unlock(LKF_CANCEL) feature. Probably the lkb->lkb_wait_count value
never reached above 1 if this feature isn't used and so it was not
discovered before.
The testcase ended in a rsb on the rsb keep data structure with a
refcount of 1 but no lkb was associated with it, which is itself
an invalid behaviour. A side effect of that was a condition in which
the dlm was sending remove messages in a looping behaviour. With this
patch that has not been reproduced.
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
Diffstat (limited to 'fs/dlm/lock.c')
-rw-r--r-- | fs/dlm/lock.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c index 1899bb266e2e..d19cfa03c9bb 100644 --- a/fs/dlm/lock.c +++ b/fs/dlm/lock.c @@ -1578,6 +1578,7 @@ static int _remove_from_waiters(struct dlm_lkb *lkb, int mstype, lkb->lkb_wait_type = 0; lkb->lkb_flags &= ~DLM_IFL_OVERLAP_CANCEL; lkb->lkb_wait_count--; + unhold_lkb(lkb); goto out_del; } @@ -1604,6 +1605,7 @@ static int _remove_from_waiters(struct dlm_lkb *lkb, int mstype, log_error(ls, "remwait error %x reply %d wait_type %d overlap", lkb->lkb_id, mstype, lkb->lkb_wait_type); lkb->lkb_wait_count--; + unhold_lkb(lkb); lkb->lkb_wait_type = 0; } @@ -5364,11 +5366,16 @@ int dlm_recover_waiters_post(struct dlm_ls *ls) lkb->lkb_flags &= ~DLM_IFL_OVERLAP_UNLOCK; lkb->lkb_flags &= ~DLM_IFL_OVERLAP_CANCEL; lkb->lkb_wait_type = 0; - lkb->lkb_wait_count = 0; + /* drop all wait_count references we still + * hold a reference for this iteration. + */ + while (lkb->lkb_wait_count) { + lkb->lkb_wait_count--; + unhold_lkb(lkb); + } mutex_lock(&ls->ls_waiters_mutex); list_del_init(&lkb->lkb_wait_reply); mutex_unlock(&ls->ls_waiters_mutex); - unhold_lkb(lkb); /* for waiters list */ if (oc || ou) { /* do an unlock or cancel instead of resending */ |