linux-kernel - [PATCH 1/2] CIFS: Fix a bug with re-sending wdata when transport returning -EAGAIN

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Message-Id: <20190302025146.2935-1-longli@linuxonhyperv.com>
Date:   Sat,  2 Mar 2019 02:51:45 +0000
From:   Long Li <longli@...uxonhyperv.com>
To:     Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org
Cc:     Long Li <longli@...rosoft.com>
Subject: [PATCH 1/2] CIFS: Fix a bug with re-sending wdata when transport returning -EAGAIN

From: Long Li <longli@...rosoft.com>

When sending a wdata, transport may return -EAGAIN. In this case
we should re-obtain credits because the session may have been
reconnected.

Signed-off-by: Long Li <longli@...rosoft.com>
---
 fs/cifs/file.c | 61 +++++++++++++++++++++++++-------------------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 9b53f33137b3..08e73759d6ec 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2620,43 +2620,44 @@ cifs_resend_wdata(struct cifs_writedata *wdata, struct list_head *wdata_list,
 	struct TCP_Server_Info *server =
 		tlink_tcon(wdata->cfile->tlink)->ses->server;
 
-	/*
-	 * Wait for credits to resend this wdata.
-	 * Note: we are attempting to resend the whole wdata not in segments
-	 */
 	do {
-		rc = server->ops->wait_mtu_credits(server, wdata->bytes, &wsize,
-						   &credits);
-
-		if (rc)
-			goto out;
-
-		if (wsize < wdata->bytes) {
-			add_credits_and_wake_if(server, &credits, 0);
-			msleep(1000);
-		}
-	} while (wsize < wdata->bytes);
+		/*
+		 * Wait for credits to resend this wdata.
+		 * Note: we are attempting to resend the whole wdata not in
+		 * segments
+		 */
+		do {
+			rc = server->ops->wait_mtu_credits(server, wdata->bytes,
+						&wsize, &credits);
+			if (rc)
+				goto fail;
+
+			if (wsize < wdata->bytes) {
+				add_credits_and_wake_if(server, &credits, 0);
+				msleep(1000);
+			}
+		} while (wsize < wdata->bytes);
 
-	wdata->credits = credits;
-	rc = -EAGAIN;
-	while (rc == -EAGAIN) {
+		wdata->credits = credits;
 		rc = 0;
 		if (wdata->cfile->invalidHandle)
 			rc = cifs_reopen_file(wdata->cfile, false);
 		if (!rc)
 			rc = server->ops->async_writev(wdata,
-					cifs_uncached_writedata_release);
-	}
+				cifs_uncached_writedata_release);
 
-	if (!rc) {
-		list_add_tail(&wdata->list, wdata_list);
-		return 0;
-	}
+		/* If the write was successfully sent, we are done */
+		if (!rc) {
+			list_add_tail(&wdata->list, wdata_list);
+			return 0;
+		}
 
-	add_credits_and_wake_if(server, &wdata->credits, 0);
-out:
-	kref_put(&wdata->refcount, cifs_uncached_writedata_release);
+		/* Roll back credits and retry if needed */
+		add_credits_and_wake_if(server, &wdata->credits, 0);
+	} while (rc == -EAGAIN);
 
+fail:
+	kref_put(&wdata->refcount, cifs_uncached_writedata_release);
 	return rc;
 }
 
@@ -2884,12 +2885,12 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx)
 						wdata->bytes, &tmp_from,
 						ctx->cfile, cifs_sb, &tmp_list,
 						ctx);
+
+					kref_put(&wdata->refcount,
+						cifs_uncached_writedata_release);
 				}
 
 				list_splice(&tmp_list, &ctx->list);
-
-				kref_put(&wdata->refcount,
-					 cifs_uncached_writedata_release);
 				goto restart_loop;
 			}
 		}
-- 
2.17.1