linux-kernel - [PATCH] CIFS: Avoid returning EBUSY to upper layer VFS

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Date:   Thu,  6 Dec 2018 04:51:06 +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,
        Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Long Li <longli@...rosoft.com>
Subject: [PATCH] CIFS: Avoid returning EBUSY to upper layer VFS

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

EBUSY is not handled by VFS, and will be passed to user-mode. This is not
correct as we need to wait for more credits.

This patch also fixes a bug where rsize or wsize is used uninitialized when
the call to server->ops->wait_mtu_credits() fails.

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Long Li <longli@...rosoft.com>
---
 fs/cifs/file.c | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 74c33d5..c9bc56b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2541,14 +2541,13 @@ static int
 cifs_resend_wdata(struct cifs_writedata *wdata, struct list_head *wdata_list,
 	struct cifs_aio_ctx *ctx)
 {
-	int wait_retry = 0;
 	unsigned int wsize, credits;
 	int rc;
 	struct TCP_Server_Info *server =
 		tlink_tcon(wdata->cfile->tlink)->ses->server;
 
 	/*
-	 * Try to resend this wdata, waiting for credits up to 3 seconds.
+	 * Wait for credits to resend this wdata.
 	 * Note: we are attempting to resend the whole wdata not in segments
 	 */
 	do {
@@ -2556,19 +2555,13 @@ cifs_resend_wdata(struct cifs_writedata *wdata, struct list_head *wdata_list,
 			server, wdata->bytes, &wsize, &credits);
 
 		if (rc)
-			break;
+			goto out;
 
 		if (wsize < wdata->bytes) {
 			add_credits_and_wake_if(server, credits, 0);
 			msleep(1000);
-			wait_retry++;
 		}
-	} while (wsize < wdata->bytes && wait_retry < 3);
-
-	if (wsize < wdata->bytes) {
-		rc = -EBUSY;
-		goto out;
-	}
+	} while (wsize < wdata->bytes);
 
 	rc = -EAGAIN;
 	while (rc == -EAGAIN) {
@@ -3234,14 +3227,13 @@ static int cifs_resend_rdata(struct cifs_readdata *rdata,
 			struct list_head *rdata_list,
 			struct cifs_aio_ctx *ctx)
 {
-	int wait_retry = 0;
 	unsigned int rsize, credits;
 	int rc;
 	struct TCP_Server_Info *server =
 		tlink_tcon(rdata->cfile->tlink)->ses->server;
 
 	/*
-	 * Try to resend this rdata, waiting for credits up to 3 seconds.
+	 * Wait for credits to resend this rdata.
 	 * Note: we are attempting to resend the whole rdata not in segments
 	 */
 	do {
@@ -3249,24 +3241,13 @@ static int cifs_resend_rdata(struct cifs_readdata *rdata,
 						&rsize, &credits);
 
 		if (rc)
-			break;
+			goto out;
 
 		if (rsize < rdata->bytes) {
 			add_credits_and_wake_if(server, credits, 0);
 			msleep(1000);
-			wait_retry++;
 		}
-	} while (rsize < rdata->bytes && wait_retry < 3);
-
-	/*
-	 * If we can't find enough credits to send this rdata
-	 * release the rdata and return failure, this will pass
-	 * whatever I/O amount we have finished to VFS.
-	 */
-	if (rsize < rdata->bytes) {
-		rc = -EBUSY;
-		goto out;
-	}
+	} while (rsize < rdata->bytes);
 
 	rc = -EAGAIN;
 	while (rc == -EAGAIN) {
-- 
2.7.4