[RFC PATCH] ceph: fix cross quota realms renames with new truncated files

[Luis Henriques]

When doing a rename across quota realms, there's a corner case that isn't
handled correctly.  Here's a testcase:

  mkdir files limit
  truncate files/file -s 10G
  setfattr limit -n ceph.quota.max_bytes -v 1000000
  mv files limit/

The above will succeed because ftruncate(2) won't result in an immediate
notification of the MDSs with the new file size, and thus the quota realms
stats won't be updated.

This patch forces a sync with the MDS every time there's an ATTR_SIZE that
sets a new i_size, even if we have Fx caps.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: dffdcd71458e ("ceph: allow rename operation under different quota realms")
URL: https://tracker.ceph.com/issues/36593
Signed-off-by: Luis Henriques <lhenriques@xxxxxxx>
---
 fs/ceph/inode.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 526faf4778ce..30e3f240ac96 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2136,15 +2136,8 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
 	if (ia_valid & ATTR_SIZE) {
 		dout("setattr %p size %lld -> %lld\n", inode,
 		     inode->i_size, attr->ia_size);
-		if ((issued & CEPH_CAP_FILE_EXCL) &&
-		    attr->ia_size > inode->i_size) {
-			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 != inode->i_size) {
+		if ((issued & (CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_SHARED)) ||
+		    (attr->ia_size != inode->i_size)) {
 			req->r_args.setattr.size = cpu_to_le64(attr->ia_size);
 			req->r_args.setattr.old_size =
 				cpu_to_le64(inode->i_size);