6.10-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
commit de40579b903883274fe203865f29d66b168b7236 upstream.
When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server.
If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting.
Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry.
The problem manifests as a warning looking something like:
WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30
Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
Fixes: 3ee1a1fc3981 ("cifs: Cut over to using netfslib") Cc: stable@vger.kernel.org Reported-by: Steve French smfrench@gmail.com Reviewed-by: Paulo Alcantara (Red Hat) pc@manguebit.com Acked-by: Tom Talpey tom@talpey.com Signed-off-by: David Howells dhowells@redhat.com cc: Jeff Layton jlayton@kernel.org cc: Aurelien Aptel aaptel@suse.com cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/client/smb2pdu.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c index 2ae2dbb6202b..bb84a89e5905 100644 --- a/fs/smb/client/smb2pdu.c +++ b/fs/smb/client/smb2pdu.c @@ -4859,9 +4859,6 @@ smb2_async_writev(struct cifs_io_subrequest *wdata) struct cifs_io_parms *io_parms = NULL; int credit_request;
- if (!wdata->server || test_bit(NETFS_SREQ_RETRYING, &wdata->subreq.flags)) - server = wdata->server = cifs_pick_channel(tcon->ses); - /* * in future we may get cifs_io_parms passed in from the caller, * but for now we construct it here...