[PATCH 3.16 326/366] ceph: don't set req->r_locked_dir in ceph_d_revalidate

Ben Hutchings
2018-11-12T05:48:23Z

From: Jeff Layton <jlayton@redhat.com>

commit c3f4688a08fd86f1bf8e055724c84b7a40a09733 upstream.

This function sets req->r_locked_dir which is supposed to indicate to
ceph_fill_trace that the parent's i_rwsem is locked for write.
Unfortunately, there is no guarantee that the dir will be locked when
d_revalidate is called, so we really don't want ceph_fill_trace to do
any dcache manipulation from this context. Clear req->r_locked_dir since
it's clearly not safe to do that.

What we really want to know with d_revalidate is whether the dentry
still points to the same inode. ceph_fill_trace installs a pointer to
the inode in req->r_target_inode, so we can just compare that to
d_inode(dentry) to see if it's the same one after the lookup.

Also, since we aren't generally interested in the parent here, we can
switch to using a GETATTR to hint that to the MDS, which also means that
we only need to reserve one cap.

Finally, just remove the d_unhashed check. That's really outside the
purview of a filesystem's d_revalidate. If the thing became unhashed
while we're checking it, then that's up to the VFS to handle anyway.

Fixes: 200fd27c8fa2 ("ceph: use lookup request to revalidate dentry")
Link: http://tracker.ceph.com/issues/18041
Reported-by: Donatas Abraitis <donatas.abraitis@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Cc: Bryan Henderson <bryanh@giraffe-data.com>
[bwh: Backported to 3.16: s/d_really_is_(positive|negative)/d_is_\1/ since
we don't have to consider overlayfs]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ceph/dir.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)

--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1071,26 +1071,30 @@ static int ceph_d_revalidate(struct dent
int op, mask, err;

op = ceph_snap(dir) == CEPH_SNAPDIR ?
- CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_LOOKUP;
+ CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_GETATTR;
req = ceph_mdsc_create_request(mdsc, op, USE_ANY_MDS);
if (!IS_ERR(req)) {
req->r_dentry = dget(dentry);
- req->r_num_caps = 2;
+ req->r_num_caps = op == CEPH_MDS_OP_GETATTR ? 1 : 2;

mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
if (ceph_security_xattr_wanted(dir))
mask |= CEPH_CAP_XATTR_SHARED;
req->r_args.getattr.mask = mask;

- req->r_locked_dir = dir;
err = ceph_mdsc_do_request(mdsc, NULL, req);
- if (err == 0 || err == -ENOENT) {
- if (dentry == req->r_dentry) {
- valid = !d_unhashed(dentry);
- } else {
- d_invalidate(req->r_dentry);
- err = -EAGAIN;
- }
+ switch (err) {
+ case 0:
+ if (d_is_positive(dentry) &&
+ d_inode(dentry) == req->r_target_inode)
+ valid = 1;
+ break;
+ case -ENOENT:
+ if (d_is_negative(dentry))
+ valid = 1;
+ /* Fallthrough */
+ default:
+ break;
}
ceph_mdsc_put_request(req);
dout("d_revalidate %p lookup result=%d\n",