[PATCH] cifs: flush all dirty pages to server before read/write

[Kinglong Mee <kinglongmee@gmail.com>]

Testing with ltp, fsx-linux fail as,

# mount -t cifs -ocache=none,nobrl,guest //cifsserverip/test /mnt/cifs/
# dd if=/dev/zero of=/mnt/cifs//junkfile bs=8192 count=19200 conv=block
# ./testcases/bin/fsx-linux -l 500000 -r 4096 -t 4096 -w 4096 -N 10000 /mnt/cifs/junkfile
skipping zero size read
truncating to largest ever: 0x2c000
READ BAD DATA: offset = 0x1c000, size = 0x9cc0
OFFSET	GOOD	BAD	RANGE
0x1c000	0x09d2	000000	0x22ed
operation# (mod 256) for the bad dataunknown, check HOLE and EXTEND ops
LOG DUMP (10 total operations):
1: 1649662377.404010 SKIPPED (no operation)
2: 1649662377.413729 WRITE    0x3000 thru 0xdece (0xaecf bytes) HOLE
3: 1649662377.424961 WRITE    0x19000 thru 0x1b410 (0x2411 bytes) HOLE
4: 1649662377.435135 TRUNCATE UP	from 0x1b411 to 0x2c000	******WWWW
5: 1649662377.487010 MAPWRITE 0x5000 thru 0x13077 (0xe078 bytes)
6: 1649662377.495006 MAPREAD  0x8000 thru 0xe16c (0x616d bytes)
7: 1649662377.500638 MAPREAD  0x1e000 thru 0x2054d (0x254e bytes)	***RRRR***
8: 1649662377.506165 WRITE    0x76000 thru 0x7993f (0x3940 bytes) HOLE
9: 1649662377.516674 MAPWRITE 0x1a000 thru 0x1e2fe (0x42ff bytes)	******WWWW
10: 1649662377.535312 READ     0x1c000 thru 0x25cbf (0x9cc0 bytes)	***RRRR***
Correct content saved for comparison
(maybe hexdump "/mnt/cifs/junkfile" vs "/mnt/cifs/junkfile.fsxgood")

Those data written at MAPWRITE is not flush to smb server, 
but the fallowing read gets data from the backend. 

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
---
 fs/cifs/file.c  | 22 ++++++++++++++++++++++
 fs/cifs/inode.c |  2 +-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d511a78383c3..11912474563e 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3222,6 +3222,7 @@ static ssize_t __cifs_writev(
 	struct kiocb *iocb, struct iov_iter *from, bool direct)
 {
 	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t total_written = 0;
 	struct cifsFileInfo *cfile;
 	struct cifs_tcon *tcon;
@@ -3249,6 +3250,16 @@ static ssize_t __cifs_writev(
 	cfile = file->private_data;
 	tcon = tlink_tcon(cfile->tlink);
 
+	/* We need to be sure that all dirty pages are written to the server. */
+	if (CIFS_CACHE_WRITE(CIFS_I(inode)) &&
+	    inode->i_mapping && inode->i_mapping->nrpages != 0) {
+		rc = filemap_write_and_wait(inode->i_mapping);
+		if (rc) {
+			mapping_set_error(inode->i_mapping, rc);
+			return rc;
+		}
+	}
+
 	if (!tcon->ses->server->ops->async_writev)
 		return -ENOSYS;
 
@@ -3961,6 +3972,7 @@ static ssize_t __cifs_readv(
 {
 	size_t len;
 	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(iocb->ki_filp);
 	struct cifs_sb_info *cifs_sb;
 	struct cifsFileInfo *cfile;
 	struct cifs_tcon *tcon;
@@ -3986,6 +3998,16 @@ static ssize_t __cifs_readv(
 	cfile = file->private_data;
 	tcon = tlink_tcon(cfile->tlink);
 
+	/* We need to be sure that all dirty pages are written to the server. */
+	if (CIFS_CACHE_WRITE(CIFS_I(inode)) &&
+	    inode->i_mapping && inode->i_mapping->nrpages != 0) {
+		rc = filemap_write_and_wait(inode->i_mapping);
+		if (rc) {
+			mapping_set_error(inode->i_mapping, rc);
+			return rc;
+		}
+	}
+
 	if (!tcon->ses->server->ops->async_readv)
 		return -ENOSYS;
 
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 2f9e7d2f81b6..d5c07196a81e 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2440,7 +2440,7 @@ int cifs_getattr(struct user_namespace *mnt_userns, const struct path *path,
 	if ((request_mask & (STATX_CTIME | STATX_MTIME | STATX_SIZE | STATX_BLOCKS)) &&
 	    !CIFS_CACHE_READ(CIFS_I(inode)) &&
 	    inode->i_mapping && inode->i_mapping->nrpages != 0) {
-		rc = filemap_fdatawait(inode->i_mapping);
+		rc = filemap_write_and_wait(inode->i_mapping);
 		if (rc) {
 			mapping_set_error(inode->i_mapping, rc);
 			return rc;
-- 
2.35.1