ceph: quota: cache inode pointer in ceph_snap_realm

Keep a pointer to the inode in struct ceph_snap_realm.  This allows to
optimize functions that walk the realms hierarchy (e.g. in quotas).

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

fs/ceph/caps.c

@@ -703,9 +703,11 @@ void ceph_add_cap(struct inode *inode,
 			}
 
 			spin_lock(&realm->inodes_with_caps_lock);
-			ci->i_snap_realm = realm;
 			list_add(&ci->i_snap_realm_item,
 				 &realm->inodes_with_caps);
+			ci->i_snap_realm = realm;
+			if (realm->ino == ci->i_vino.ino)
+				realm->inode = inode;
 			spin_unlock(&realm->inodes_with_caps_lock);
 
 			if (oldrealm)

fs/ceph/inode.c

@@ -551,6 +551,9 @@ void ceph_destroy_inode(struct inode *inode)
 		dout(" dropping residual ref to snap realm %p\n", realm);
 		spin_lock(&realm->inodes_with_caps_lock);
 		list_del_init(&ci->i_snap_realm_item);
+		ci->i_snap_realm = NULL;
+		if (realm->ino == ci->i_vino.ino)
+			realm->inode = NULL;
 		spin_unlock(&realm->inodes_with_caps_lock);
 		ceph_put_snap_realm(mdsc, realm);
 	}

fs/ceph/quota.c

@@ -83,7 +83,6 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
 {
 	struct ceph_inode_info *ci = NULL;
 	struct ceph_snap_realm *realm, *next;
-	struct ceph_vino vino;
 	struct inode *in;
 	bool has_quota;
 
@@ -97,13 +96,12 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
 		pr_err_ratelimited("get_quota_realm: ino (%llx.%llx) "
 				   "null i_snap_realm\n", ceph_vinop(inode));
 	while (realm) {
-		vino.ino = realm->ino;
-		vino.snap = CEPH_NOSNAP;
-		in = ceph_find_inode(inode->i_sb, vino);
-		if (!in) {
-			pr_warn("Failed to find inode for %llu\n", vino.ino);
+		spin_lock(&realm->inodes_with_caps_lock);
+		in = realm->inode ? igrab(realm->inode) : NULL;
+		spin_unlock(&realm->inodes_with_caps_lock);
+		if (!in)
 			break;
-		}
+
 		ci = ceph_inode(in);
 		has_quota = ceph_has_quota(ci);
 		iput(in);
@@ -161,7 +159,6 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
 	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
 	struct ceph_inode_info *ci;
 	struct ceph_snap_realm *realm, *next;
-	struct ceph_vino vino;
 	struct inode *in;
 	u64 max, rvalue;
 	bool exceeded = false;
@@ -177,13 +174,12 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
 		pr_err_ratelimited("check_quota_exceeded: ino (%llx.%llx) "
 				   "null i_snap_realm\n", ceph_vinop(inode));
 	while (realm) {
-		vino.ino = realm->ino;
-		vino.snap = CEPH_NOSNAP;
-		in = ceph_find_inode(inode->i_sb, vino);
-		if (!in) {
-			pr_warn("Failed to find inode for %llu\n", vino.ino);
+		spin_lock(&realm->inodes_with_caps_lock);
+		in = realm->inode ? igrab(realm->inode) : NULL;
+		spin_unlock(&realm->inodes_with_caps_lock);
+		if (!in)
 			break;
-		}
+
 		ci = ceph_inode(in);
 		spin_lock(&ci->i_ceph_lock);
 		if (op == QUOTA_CHECK_MAX_FILES_OP) {

fs/ceph/snap.c

@@ -931,6 +931,8 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 			list_add(&ci->i_snap_realm_item,
 				 &realm->inodes_with_caps);
 			ci->i_snap_realm = realm;
+			if (realm->ino == ci->i_vino.ino)
+                                realm->inode = inode;
 			spin_unlock(&realm->inodes_with_caps_lock);
 
 			spin_unlock(&ci->i_ceph_lock);

fs/ceph/super.h

@@ -755,6 +755,7 @@ struct ceph_readdir_cache_control {
  */
 struct ceph_snap_realm {
 	u64 ino;
+	struct inode *inode;
 	atomic_t nref;
 	struct rb_node node;