[PATCH] ceph: fix statfs for subdir mounts

["Luís Henriques" <lhenriques@suse.de>]

When doing a mount using as base a directory that has 'max_bytes' quotas
statfs uses that value as the total; if a subdirectory is used instead,
the same 'max_bytes' too in statfs, unless there is another quota set.

Unfortunately, if this subdirectory only has the 'max_files' quota set,
then statfs uses the filesystem total.  Fix this by making sure we only
lookup realms that contain the 'max_bytes' quota.

Link: https://tracker.ceph.com/issues/55090
Cc: Ryan Taylor <rptaylor@uvic.ca>
Signed-off-by: Luís Henriques <lhenriques@suse.de>
---
Hi!

Unfortunately, I don't think this is the real fix for the bug reported in
the tracker (or by Ryan on the mailing-list).  I haven't seen any
reference to 'max_files' so I suspect Ryan and Dan are hitting another
bug.  This can be easily checked by 'getfattr -n ceph.quota <subdir>'.

Also, Dan (in the tracker) states the bug is on the kernel client only but
I can also see if in the fuse client.

Anyway, this patch fixes a real bug.

 fs/ceph/quota.c | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index a338a3ec0dc4..235a8d06a8ee 100644
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -193,11 +193,17 @@ void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)
 	mutex_unlock(&mdsc->quotarealms_inodes_mutex);
 }
 
+enum quota_get_realm {
+	QUOTA_GET_MAX_FILES,
+	QUOTA_GET_MAX_BYTES,
+	QUOTA_GET_ANY
+};
+
 /*
  * This function walks through the snaprealm for an inode and returns the
- * ceph_snap_realm for the first snaprealm that has quotas set (either max_files
- * or max_bytes).  If the root is reached, return the root ceph_snap_realm
- * instead.
+ * ceph_snap_realm for the first snaprealm that has quotas set (max_files,
+ * max_bytes, or any, depending on the 'which_quota' argument).  If the root is
+ * reached, return the root ceph_snap_realm instead.
  *
  * Note that the caller is responsible for calling ceph_put_snap_realm() on the
  * returned realm.
@@ -209,7 +215,9 @@ void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)
  * will be restarted.
  */
 static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
-					       struct inode *inode, bool retry)
+					       struct inode *inode,
+					       enum quota_get_realm which_quota,
+					       bool retry)
 {
 	struct ceph_inode_info *ci = NULL;
 	struct ceph_snap_realm *realm, *next;
@@ -248,7 +256,17 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
 		}
 
 		ci = ceph_inode(in);
-		has_quota = __ceph_has_any_quota(ci);
+		switch (which_quota) {
+		case QUOTA_GET_MAX_BYTES:
+			has_quota = ci->i_max_bytes;
+			break;
+		case QUOTA_GET_MAX_FILES:
+			has_quota = ci->i_max_files;
+			break;
+		default: /* QUOTA_GET_ANY */
+			has_quota = __ceph_has_any_quota(ci);
+			break;
+		}
 		iput(in);
 
 		next = realm->parent;
@@ -279,8 +297,8 @@ bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)
 	 * dropped and we can then restart the whole operation.
 	 */
 	down_read(&mdsc->snap_rwsem);
-	old_realm = get_quota_realm(mdsc, old, true);
-	new_realm = get_quota_realm(mdsc, new, false);
+	old_realm = get_quota_realm(mdsc, old, QUOTA_GET_ANY, true);
+	new_realm = get_quota_realm(mdsc, new, QUOTA_GET_ANY, false);
 	if (PTR_ERR(new_realm) == -EAGAIN) {
 		up_read(&mdsc->snap_rwsem);
 		if (old_realm)
@@ -483,7 +501,8 @@ bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
 	bool is_updated = false;
 
 	down_read(&mdsc->snap_rwsem);
-	realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root), true);
+	realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root),
+				QUOTA_GET_MAX_BYTES, true);
 	up_read(&mdsc->snap_rwsem);
 	if (!realm)
 		return false;