ceph: quota: report root dir quota usage in statfs

This commit changes statfs default behaviour when reporting usage
statistics.  Instead of using the overall filesystem usage, statfs now
reports the quota for the filesystem root, if ceph.quota.max_bytes has
been set for this inode.  If quota hasn't been set, it falls back to the
old statfs behaviour.

A new mount option is also added ('noquotadf') to disable this behaviour.

Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index 588744b4665f..242bfa5c0539 100644
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -18,6 +18,8 @@
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/statfs.h>
+
 #include "super.h"
 #include "mds_client.h"
 
@@ -303,3 +305,57 @@ bool ceph_quota_is_max_bytes_approaching(struct inode *inode, loff_t newsize)
 	return check_quota_exceeded(inode, QUOTA_CHECK_MAX_BYTES_APPROACHING_OP,
 				    (newsize - size));
 }
+
+/*
+ * ceph_quota_update_statfs - if root has quota update statfs with quota status
+ * @fsc:	filesystem client instance
+ * @buf:	statfs to update
+ *
+ * If the mounted filesystem root has max_bytes quota set, update the filesystem
+ * statistics with the quota status.
+ *
+ * This function returns true if the stats have been updated, false otherwise.
+ */
+bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
+{
+	struct ceph_mds_client *mdsc = fsc->mdsc;
+	struct ceph_inode_info *ci;
+	struct ceph_snap_realm *realm;
+	struct inode *in;
+	u64 total = 0, used, free;
+	bool is_updated = false;
+
+	down_read(&mdsc->snap_rwsem);
+	realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root));
+	up_read(&mdsc->snap_rwsem);
+	if (!realm)
+		return false;
+
+	spin_lock(&realm->inodes_with_caps_lock);
+	in = realm->inode ? igrab(realm->inode) : NULL;
+	spin_unlock(&realm->inodes_with_caps_lock);
+	if (in) {
+		ci = ceph_inode(in);
+		spin_lock(&ci->i_ceph_lock);
+		if (ci->i_max_bytes) {
+			total = ci->i_max_bytes >> CEPH_BLOCK_SHIFT;
+			used = ci->i_rbytes >> CEPH_BLOCK_SHIFT;
+			/* It is possible for a quota to be exceeded.
+			 * Report 'zero' in that case
+			 */
+			free = total > used ? total - used : 0;
+		}
+		spin_unlock(&ci->i_ceph_lock);
+		if (total) {
+			buf->f_blocks = total;
+			buf->f_bfree = free;
+			buf->f_bavail = free;
+			is_updated = true;
+		}
+		iput(in);
+	}
+	ceph_put_snap_realm(mdsc, realm);
+
+	return is_updated;
+}
+