ceph: ignore the truncate when size won't change with Fx caps issued

If the new size is the same as the current size, the MDS will do nothing
but change the mtime/atime. POSIX doesn't mandate that the filesystems
must update them in this case, so just ignore it instead.

Signed-off-by: Xiubo Li <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Signed-off-by: Ilya Dryomov <[email protected]>

Author: lxbsz

fs/ceph/inode.c

@@ -2103,12 +2103,14 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
 		loff_t isize = i_size_read(inode);
 
 		dout("setattr %p size %lld -> %lld\n", inode, isize, attr->ia_size);
-		if ((issued & CEPH_CAP_FILE_EXCL) && attr->ia_size > isize) {
-			i_size_write(inode, attr->ia_size);
-			inode->i_blocks = calc_inode_blocks(attr->ia_size);
-			ci->i_reported_size = attr->ia_size;
-			dirtied |= CEPH_CAP_FILE_EXCL;
-			ia_valid |= ATTR_MTIME;
+		if ((issued & CEPH_CAP_FILE_EXCL) && attr->ia_size >= isize) {
+			if (attr->ia_size > isize) {
+				i_size_write(inode, attr->ia_size);
+				inode->i_blocks = calc_inode_blocks(attr->ia_size);
+				ci->i_reported_size = attr->ia_size;
+				dirtied |= CEPH_CAP_FILE_EXCL;
+				ia_valid |= ATTR_MTIME;
+			}
 		} else if ((issued & CEPH_CAP_FILE_SHARED) == 0 ||
 			   attr->ia_size != isize) {
 			req->r_args.setattr.size = cpu_to_le64(attr->ia_size);