From: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Date: Wed, 7 Jul 2021 19:16:00 +0000 (-0400)
Subject: LU-14733 o2iblnd: Move racy NULL assignment
X-Git-Tag: 2.14.53~54
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=023113fb8946f3565529e7327fdcd90ab9db3ba3;hp=7ac839837c1c6cd1ff629c7898349db8cc55891d

LU-14733 o2iblnd: Move racy NULL assignment

kiblnd_fmr_pool_unmap() can race map and subsequent processing
because of this flaw in unmap:

	if (frd) {
		frd->frd_valid = false;
		spin_lock(&fps->fps_lock);
		list_add_tail(&frd->frd_list, &fpo->fast_reg.fpo_pool_list);
		spin_unlock(&fps->fps_lock);
		fmr->fmr_frd = NULL;
	}

The fmr can be pulled off the list in kiblnd_fmr_pool_unmap() on
another CPU an fmr_frd could be in a state of flux and
potentially be seen incorrectly later on as the kib_tx is processed.

Fix my moving the fmr_frd assignment to before the fmr is added to the
list.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Change-Id: Ibddf132a363ecfe9db3cc06287cec873c021d2fb
Reviewed-on: https://review.whamcloud.com/44189
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lnet/klnds/o2iblnd/o2iblnd.c b/lnet/klnds/o2iblnd/o2iblnd.c
index b28c5b2..f3028b4 100644
--- a/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/lnet/klnds/o2iblnd/o2iblnd.c
@@ -1751,10 +1751,10 @@ kiblnd_fmr_pool_unmap(struct kib_fmr *fmr, int status)
 
 		if (frd) {
 			frd->frd_valid = false;
+			fmr->fmr_frd = NULL;
 			spin_lock(&fps->fps_lock);
 			list_add_tail(&frd->frd_list, &fpo->fast_reg.fpo_pool_list);
 			spin_unlock(&fps->fps_lock);
-			fmr->fmr_frd = NULL;
 		}
 	}
 	fmr->fmr_pool = NULL;