cifs: fix fallocate when trying to allocate a hole.

Remove the conditional checking for out_data_len and skipping the fallocate
if it is 0. This is wrong will actually change any legitimate the fallocate
where the entire region is unallocated into a no-op.

Additionally, before allocating the range, if FALLOC_FL_KEEP_SIZE is set then
we need to clamp the length of the fallocate region as to not extend the size of the file.

Fixes: 966a3cb7c7db ("cifs: improve fallocate emulation")
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 5cefb59..23d6f4d 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3667,11 +3667,6 @@ static int smb3_simple_fallocate_range(unsigned int xid,
                        (char **)&out_data, &out_data_len);
        if (rc)
                goto out;
-       /*
-        * It is already all allocated
-        */
-       if (out_data_len == 0)
-               goto out;
 
        buf = kzalloc(1024 * 1024, GFP_KERNEL);
        if (buf == NULL) {
@@ -3794,6 +3789,24 @@ static long smb3_simple_falloc(struct file *file, struct cifs_tcon *tcon,
                goto out;
        }
 
+       if (keep_size == true) {
+               /*
+                * We can not preallocate pages beyond the end of the file
+                * in SMB2
+                */
+               if (off >= i_size_read(inode)) {
+                       rc = 0;
+                       goto out;
+               }
+               /*
+                * For fallocates that are partially beyond the end of file,
+                * clamp len so we only fallocate up to the end of file.
+                */
+               if (off + len > i_size_read(inode)) {
+                       len = i_size_read(inode) - off;
+               }
+       }
+
        if ((keep_size == true) || (i_size_read(inode) >= off + len)) {
                /*
                 * At this point, we are trying to fallocate an internal