[PATCH 5.10 103/167] cifs: only write 64kb at a time when fallocating a small region of a file

From: Greg Kroah-Hartman
Date: Mon Jul 26 2021 - 12:23:28 EST


From: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>

[ Upstream commit 2485bd7557a7edb4520b4072af464f0a08c8efe0 ]

We only allow sending single credit writes through the SMB2_write() synchronous
api so split this into smaller chunks.

Fixes: 966a3cb7c7db ("cifs: improve fallocate emulation")

Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
Reported-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/cifs/smb2ops.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f6ceb79a995d..442bf422aa01 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3466,7 +3466,7 @@ static int smb3_simple_fallocate_write_range(unsigned int xid,
char *buf)
{
struct cifs_io_parms io_parms = {0};
- int nbytes;
+ int rc, nbytes;
struct kvec iov[2];

io_parms.netfid = cfile->fid.netfid;
@@ -3474,13 +3474,25 @@ static int smb3_simple_fallocate_write_range(unsigned int xid,
io_parms.tcon = tcon;
io_parms.persistent_fid = cfile->fid.persistent_fid;
io_parms.volatile_fid = cfile->fid.volatile_fid;
- io_parms.offset = off;
- io_parms.length = len;

- /* iov[0] is reserved for smb header */
- iov[1].iov_base = buf;
- iov[1].iov_len = io_parms.length;
- return SMB2_write(xid, &io_parms, &nbytes, iov, 1);
+ while (len) {
+ io_parms.offset = off;
+ io_parms.length = len;
+ if (io_parms.length > SMB2_MAX_BUFFER_SIZE)
+ io_parms.length = SMB2_MAX_BUFFER_SIZE;
+ /* iov[0] is reserved for smb header */
+ iov[1].iov_base = buf;
+ iov[1].iov_len = io_parms.length;
+ rc = SMB2_write(xid, &io_parms, &nbytes, iov, 1);
+ if (rc)
+ break;
+ if (nbytes > len)
+ return -EINVAL;
+ buf += nbytes;
+ off += nbytes;
+ len -= nbytes;
+ }
+ return rc;
}

static int smb3_simple_fallocate_range(unsigned int xid,
--
2.30.2