cifs: only write 64kb at a time when fallocating a small region of a file

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@redhat.com>
Reported-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index ba3c58e..5cefb59 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3617,7 +3617,7 @@ 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;
@@ -3625,13 +3625,25 @@ 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,