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To: Steve French <sfrench@samba.org>, Paulo Alcantara <pc@manguebit.com>
cc: dhowells@redhat.com, Shyam Prasad N <nspmangalore@gmail.com>,
    Rohith Surabattula <rohiths.msft@gmail.com>,
    Jeff Layton <jlayton@kernel.org>, linux-cifs@vger.kernel.org,
    netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org,
    linux-kernel@vger.kernel.org
Subject: [RFC PATCH] cifs: Fix credit handling in cifs_io_subrequest cleanup
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From: David Howells <dhowells@redhat.com>
Date: Wed, 22 May 2024 23:59:02 +0100
Message-ID: <469451.1716418742@warthog.procyon.org.uk>

    =

When a cifs_io_subrequest (wrapping a netfs_io_subrequest) is cleaned up i=
n
cifs_free_subrequest(), it releases any credits that are left in
rdata->credits.  However, this is a problem because smb2_writev_callback()
calls add_credits() to add the new credits from the response header
CreditRequest to the available pool.

This can cause a warning to be emitted in smb2_add_credits() as
server->in_flight gets doubly decremented and a later operation sees it
having prematurely reached 0.

Fix this by clearing the credit count after actually issuing the request o=
n
the assumption that we've given the credits back to the server (it will
give us new credits in the reply).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/smb/client/file.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 9d5c2440abfc..73e2765c4d2f 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -110,6 +110,7 @@ static void cifs_issue_write(struct netfs_io_subreques=
t *subreq)
 		goto fail;
 =

 	wdata->server->ops->async_writev(wdata);
+	wdata->credits.value =3D 0;
 out:
 	return;
 =

@@ -205,10 +206,12 @@ static void cifs_req_issue_read(struct netfs_io_subr=
equest *subreq)
 =

 	rc =3D adjust_credits(rdata->server, &rdata->credits, rdata->subreq.len)=
;
 	if (!rc) {
-		if (rdata->req->cfile->invalidHandle)
+		if (rdata->req->cfile->invalidHandle) {
 			rc =3D -EAGAIN;
-		else
+		} else {
 			rc =3D rdata->server->ops->async_readv(rdata);
+			rdata->credits.value =3D 0;
+		}
 	}
 =

 out: