FAILED: patch "[PATCH] nfsd: fix delegation_blocked() to block correctly for at" failed to apply to 4.19-stable tree

FAILED: patch "[PATCH] nfsd: fix delegation_blocked() to block correctly for at" failed to apply to 4.19-stable tree

[gregkh]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 45bb63ed20e02ae146336412889fe5450316a84f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024100729-trident-control-06ad@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

45bb63ed20e0 ("nfsd: fix delegation_blocked() to block correctly for at least 30 seconds")
b3f255ef6bff ("nfsd: use ktime_get_seconds() for timestamps")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 45bb63ed20e02ae146336412889fe5450316a84f Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 9 Sep 2024 15:06:36 +1000
Subject: [PATCH] nfsd: fix delegation_blocked() to block correctly for at
 least 30 seconds

The pair of bloom filtered used by delegation_blocked() was intended to
block delegations on given filehandles for between 30 and 60 seconds.  A
new filehandle would be recorded in the "new" bit set.  That would then
be switch to the "old" bit set between 0 and 30 seconds later, and it
would remain as the "old" bit set for 30 seconds.

Unfortunately the code intended to clear the old bit set once it reached
30 seconds old, preparing it to be the next new bit set, instead cleared
the *new* bit set before switching it to be the old bit set.  This means
that the "old" bit set is always empty and delegations are blocked
between 0 and 30 seconds.

This patch updates bd->new before clearing the set with that index,
instead of afterwards.

Reported-by: Olga Kornievskaia <okorniev@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 6282cd565553 ("NFSD: Don't hand out delegations for 30 seconds after recalling them.")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index cb5a9ab451c5..ac1859c7cc9d 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1078,7 +1078,8 @@ static void nfs4_free_deleg(struct nfs4_stid *stid)
  * When a delegation is recalled, the filehandle is stored in the "new"
  * filter.
  * Every 30 seconds we swap the filters and clear the "new" one,
- * unless both are empty of course.
+ * unless both are empty of course.  This results in delegations for a
+ * given filehandle being blocked for between 30 and 60 seconds.
  *
  * Each filter is 256 bits.  We hash the filehandle to 32bit and use the
  * low 3 bytes as hash-table indices.
@@ -1107,9 +1108,9 @@ static int delegation_blocked(struct knfsd_fh *fh)
 		if (ktime_get_seconds() - bd->swap_time > 30) {
 			bd->entries -= bd->old_entries;
 			bd->old_entries = bd->entries;
+			bd->new = 1-bd->new;
 			memset(bd->set[bd->new], 0,
 			       sizeof(bd->set[0]));
-			bd->new = 1-bd->new;
 			bd->swap_time = ktime_get_seconds();
 		}
 		spin_unlock(&blocked_delegations_lock);