linux-kernel - [PATCH 4.10 18/69] CIFS: store results of cifs_reopen

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Date:   Wed, 19 Apr 2017 16:36:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Germano Percossi <germano.percossi@...rix.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>,
        Steve French <smfrench@...il.com>
Subject: [PATCH 4.10 18/69] CIFS: store results of cifs_reopen_file to avoid infinite wait

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Germano Percossi <germano.percossi@...rix.com>

commit 1fa839b4986d648b907d117275869a0e46c324b9 upstream.

This fixes Continuous Availability when errors during
file reopen are encountered.

cifs_user_readv and cifs_user_writev would wait for ever if
results of cifs_reopen_file are not stored and for later inspection.

In fact, results are checked and, in case of errors, a chain
of function calls leading to reads and writes to be scheduled in
a separate thread is skipped.
These threads will wake up the corresponding waiters once reads
and writes are done.

However, given the return value is not stored, when rc is checked
for errors a previous one (always zero) is inspected instead.
This leads to pending reads/writes added to the list, making
cifs_user_readv and cifs_user_writev wait for ever.

Signed-off-by: Germano Percossi <germano.percossi@...rix.com>
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Steve French <smfrench@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/cifs/file.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2597,7 +2597,7 @@ cifs_write_from_iter(loff_t offset, size
 		wdata->credits = credits;
 
 		if (!wdata->cfile->invalidHandle ||
-		    !cifs_reopen_file(wdata->cfile, false))
+		    !(rc = cifs_reopen_file(wdata->cfile, false)))
 			rc = server->ops->async_writev(wdata,
 					cifs_uncached_writedata_release);
 		if (rc) {
@@ -3002,7 +3002,7 @@ cifs_send_async_read(loff_t offset, size
 		rdata->credits = credits;
 
 		if (!rdata->cfile->invalidHandle ||
-		    !cifs_reopen_file(rdata->cfile, true))
+		    !(rc = cifs_reopen_file(rdata->cfile, true)))
 			rc = server->ops->async_readv(rdata);
 error:
 		if (rc) {
@@ -3577,7 +3577,7 @@ static int cifs_readpages(struct file *f
 		}
 
 		if (!rdata->cfile->invalidHandle ||
-		    !cifs_reopen_file(rdata->cfile, true))
+		    !(rc = cifs_reopen_file(rdata->cfile, true)))
 			rc = server->ops->async_readv(rdata);
 		if (rc) {
 			add_credits_and_wake_if(server, rdata->credits, 0);