[PATCH] cifs: Detect errors in cifs_writepages when called during background write-back

The return code isn't checked in the case of cifs_writepages being
invoked as a result of pdflush and potentially other background
write-back. This results in data integrity problems when errors such as
a network break occur when CIFSSMBWrite2 is called.  The resulting error
isn't acted on.  This patch hangs on to the write-behind error so that it
is available for detection later on.

Signed-off-by: Peter Schwenke <[email protected]>
---
 fs/cifs/file.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 042b122..f1a5b1e 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1200,6 +1200,7 @@ static int cifs_writepages(struct address_space *mapping,
 	unsigned int bytes_to_write;
 	unsigned int bytes_written;
 	struct cifs_sb_info *cifs_sb;
+	struct cifsInodeInfo *cifs_inode = CIFS_I(mapping->host);
 	int done = 0;
 	pgoff_t end;
 	pgoff_t index;
@@ -1354,7 +1355,7 @@ retry:
 			 * CIFSSMBWrite2.  We can't rely on the last handle
 			 * we used to still be valid
 			 */
-			open_file = find_writable_file(CIFS_I(mapping->host));
+			open_file = find_writable_file(cifs_inode);
 			if (!open_file) {
 				cERROR(1, ("No writable handles for inode"));
 				rc = -EBADF;
@@ -1374,6 +1375,18 @@ retry:
 						set_bit(AS_ENOSPC, &mapping->flags);
 					else
 						set_bit(AS_EIO, &mapping->flags);
+					/*
+					 * The return code isn't checked in the
+					 * case of cifs_writepages being
+					 * invoked from background write outs
+					 * i.e. generic_sync_sb_inodes()
+					 */
+					if (wbc->sync_mode == WB_SYNC_NONE) {
+						if (rc == -ENOSPC)
+							cifs_inode->write_behind_rc =  rc;
+						else
+							cifs_inode->write_behind_rc =  -EIO;
+					}
 				} else {
 					cifs_stats_bytes_written(cifs_sb->tcon,
 								 bytes_written);
-- 
1.5.4.3