diff mbox series

[5/8] afs: Fix possible infinite loop with unresponsive servers

Message ID 20240923150756.902363-6-dhowells@redhat.com
State New
Headers show
Series netfs, afs, cifs: Miscellaneous fixes/changes | expand

Commit Message

David Howells Sept. 23, 2024, 3:07 p.m. UTC 
From: Marc Dionne <marc.dionne@auristor.com>

A return code of 0 from afs_wait_for_one_fs_probe is an indication
that the endpoint state attached to the operation is stale and has
been superseded.  In that case the iteration needs to be restarted
so that the newer probe result state gets used.

Failure to do so can result in an tight infinite loop around the
iterate_address label, where all addresses are thought to be responsive
and have been tried, with nothing to refresh the endpoint state.

Fixes: 495f2ae9e355 ("afs: Fix fileserver rotation")
Reported-by: Markus Suvanto <markus.suvanto@gmail.com>
Link: https://lists.infradead.org/pipermail/linux-afs/2024-July/008628.html
cc: linux-afs@lists.infradead.org
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20240906134019.131553-1-marc.dionne@auristor.com/
---
 fs/afs/fs_probe.c |  4 ++--
 fs/afs/rotate.c   | 11 ++++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

Comments

Christian Brauner Sept. 27, 2024, 8:05 a.m. UTC | #1 
On Mon, 23 Sep 2024 16:07:49 +0100, David Howells wrote:
> A return code of 0 from afs_wait_for_one_fs_probe is an indication
> that the endpoint state attached to the operation is stale and has
> been superseded.  In that case the iteration needs to be restarted
> so that the newer probe result state gets used.
> 
> Failure to do so can result in an tight infinite loop around the
> iterate_address label, where all addresses are thought to be responsive
> and have been tried, with nothing to refresh the endpoint state.
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[5/8] afs: Fix possible infinite loop with unresponsive servers
      https://git.kernel.org/vfs/vfs/c/6e45740867ee
diff mbox series

Patch

diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c
index 580de4adaaf6..b516d05b0fef 100644
--- a/fs/afs/fs_probe.c
+++ b/fs/afs/fs_probe.c
@@ -506,10 +506,10 @@  int afs_wait_for_one_fs_probe(struct afs_server *server, struct afs_endpoint_sta
 	finish_wait(&server->probe_wq, &wait);
 
 dont_wait:
-	if (estate->responsive_set & ~exclude)
-		return 1;
 	if (test_bit(AFS_ESTATE_SUPERSEDED, &estate->flags))
 		return 0;
+	if (estate->responsive_set & ~exclude)
+		return 1;
 	if (is_intr && signal_pending(current))
 		return -ERESTARTSYS;
 	if (timo == 0)
diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
index ed09d4d4c211..d612983d6f38 100644
--- a/fs/afs/rotate.c
+++ b/fs/afs/rotate.c
@@ -632,8 +632,10 @@  bool afs_select_fileserver(struct afs_operation *op)
 wait_for_more_probe_results:
 	error = afs_wait_for_one_fs_probe(op->server, op->estate, op->addr_tried,
 					  !(op->flags & AFS_OPERATION_UNINTR));
-	if (!error)
+	if (error == 1)
 		goto iterate_address;
+	if (!error)
+		goto restart_from_beginning;
 
 	/* We've now had a failure to respond on all of a server's addresses -
 	 * immediately probe them again and consider retrying the server.
@@ -644,10 +646,13 @@  bool afs_select_fileserver(struct afs_operation *op)
 		error = afs_wait_for_one_fs_probe(op->server, op->estate, op->addr_tried,
 						  !(op->flags & AFS_OPERATION_UNINTR));
 		switch (error) {
-		case 0:
+		case 1:
 			op->flags &= ~AFS_OPERATION_RETRY_SERVER;
-			trace_afs_rotate(op, afs_rotate_trace_retry_server, 0);
+			trace_afs_rotate(op, afs_rotate_trace_retry_server, 1);
 			goto retry_server;
+		case 0:
+			trace_afs_rotate(op, afs_rotate_trace_retry_server, 0);
+			goto restart_from_beginning;
 		case -ERESTARTSYS:
 			afs_op_set_error(op, error);
 			goto failed;