ceph: allow ceph.dir.rctime xattr to be updatable

`rctime' has been a pain point in cephfs due to its buggy
nature - inconsistent values reported and those sorts.
Fixing rctime is non-trivial needing an overall redesign
of the entire nested statistics infrastructure.

As a workaround, PR

     http://github.com/ceph/ceph/pull/37938

allows this extended attribute to be manually set. This allows
users to "fixup" inconsistent rctime values. While this sounds
messy, its probably the wisest approach allowing users/scripts
to workaround buggy rctime values.

The above PR enables Ceph MDS to allow manually setting
rctime extended attribute with the corresponding user-land
changes. We may as well allow the same to be done via kclient
for parity.

Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index afec840..8c2dc2c 100644 (file)
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -366,6 +366,14 @@ static ssize_t ceph_vxattrcb_auth_mds(struct ceph_inode_info *ci,
        }
 #define XATTR_RSTAT_FIELD(_type, _name)                        \
        XATTR_NAME_CEPH(_type, _name, VXATTR_FLAG_RSTAT)
+#define XATTR_RSTAT_FIELD_UPDATABLE(_type, _name)                      \
+       {                                                               \
+               .name = CEPH_XATTR_NAME(_type, _name),                  \
+               .name_size = sizeof (CEPH_XATTR_NAME(_type, _name)),    \
+               .getxattr_cb = ceph_vxattrcb_ ## _type ## _ ## _name,   \
+               .exists_cb = NULL,                                      \
+               .flags = VXATTR_FLAG_RSTAT,                             \
+       }
 #define XATTR_LAYOUT_FIELD(_type, _name, _field)                       \
        {                                                               \
                .name = CEPH_XATTR_NAME2(_type, _name, _field), \
@@ -404,7 +412,7 @@ static struct ceph_vxattr ceph_dir_vxattrs[] = {
        XATTR_RSTAT_FIELD(dir, rsubdirs),
        XATTR_RSTAT_FIELD(dir, rsnaps),
        XATTR_RSTAT_FIELD(dir, rbytes),
-       XATTR_RSTAT_FIELD(dir, rctime),
+       XATTR_RSTAT_FIELD_UPDATABLE(dir, rctime),
        {
                .name = "ceph.dir.pin",
                .name_size = sizeof("ceph.dir.pin"),