[PATCH 6.0 065/124] afs: Fix fileserver probe RTT handling

Greg Kroah-Hartman
2022-12-05T19:26:53Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit ca57f02295f188d6c65ec02202402979880fa6d8 ]

The fileserver probing code attempts to work out the best fileserver to
use for a volume by retrieving the RTT calculated by AF_RXRPC for the
probe call sent to each server and comparing them. Sometimes, however,
no RTT estimate is available and rxrpc_kernel_get_srtt() returns false,
leading good fileservers to be given an RTT of UINT_MAX and thus causing
the rotation algorithm to ignore them.

Fix afs_select_fileserver() to ignore rxrpc_kernel_get_srtt()'s return
value and just take the estimated RTT it provides - which will be capped
at 1 second.

Fixes: 1d4adfaf6574 ("rxrpc: Make rxrpc_kernel_get_srtt() indicate validity")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/166965503999.3392585.13954054113218099395.stgit@warthog.procyon.org.uk/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/afs/fs_probe.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c
index c0031a3ab42f..3ac5fcf98d0d 100644
--- a/fs/afs/fs_probe.c
+++ b/fs/afs/fs_probe.c
@@ -167,8 +167,8 @@ void afs_fileserver_probe_result(struct afs_call *call)
clear_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
}

- if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
- rtt_us < server->probe.rtt) {
+ rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us);
+ if (rtt_us < server->probe.rtt) {
server->probe.rtt = rtt_us;
server->rtt = rtt_us;
alist->preferred = index;
--
2.35.1