ceph: map snapid to anonymous bdev ID

ceph_getattr() return zero dev ID for head inodes and set dev ID to
snapid directly for snaphost inodes. This is not good because userspace
utilities may consider device ID of 0 as invalid, snapid may conflict
with other device's ID.

This patch introduces "snapids to anonymous bdev IDs" map. we create a
new mapping when we see a snapid for the first time. we trim unused
mapping after it is ilde for 5 minutes.

Link: http://tracker.ceph.com/issues/22353
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index c080b13..7f82cef 100644 (file)
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -548,17 +548,22 @@ void ceph_destroy_inode(struct inode *inode)
         */
        if (ci->i_snap_realm) {
                struct ceph_mds_client *mdsc =
-                       ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
-               struct ceph_snap_realm *realm = ci->i_snap_realm;
-
-               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);
+                                       ceph_inode_to_client(inode)->mdsc;
+               if (ceph_snap(inode) == CEPH_NOSNAP) {
+                       struct ceph_snap_realm *realm = ci->i_snap_realm;
+                       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);
+               } else {
+                       ceph_put_snapid_map(mdsc, ci->i_snapid_map);
+                       ci->i_snap_realm = NULL;
+               }
        }
 
        kfree(ci->i_symlink);
@@ -776,6 +781,9 @@ static int fill_inode(struct inode *inode, struct page *locked_page,
                pool_ns = ceph_find_or_create_string(iinfo->pool_ns_data,
                                                     iinfo->pool_ns_len);
 
+       if (ceph_snap(inode) != CEPH_NOSNAP && !ci->i_snapid_map)
+               ci->i_snapid_map = ceph_get_snapid_map(mdsc, ceph_snap(inode));
+
        spin_lock(&ci->i_ceph_lock);
 
        /*
@@ -2260,10 +2268,11 @@ int ceph_getattr(const struct path *path, struct kstat *stat,
        if (!err) {
                generic_fillattr(inode, stat);
                stat->ino = ceph_translate_ino(inode->i_sb, inode->i_ino);
-               if (ceph_snap(inode) != CEPH_NOSNAP)
-                       stat->dev = ceph_snap(inode);
+               if (ceph_snap(inode) == CEPH_NOSNAP)
+                       stat->dev = inode->i_sb->s_dev;
                else
-                       stat->dev = 0;
+                       stat->dev = ci->i_snapid_map ? ci->i_snapid_map->dev : 0;
+
                if (S_ISDIR(inode->i_mode)) {
                        if (ceph_test_mount_opt(ceph_sb_to_client(inode->i_sb),
                                                RBYTES))

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index cce4e4b..f2f5777 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3791,6 +3791,8 @@ static void delayed_work(struct work_struct *work)
        dout("mdsc delayed_work\n");
        ceph_check_delayed_caps(mdsc);
 
+       ceph_trim_snapid_map(mdsc);
+
        mutex_lock(&mdsc->mutex);
        renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
        renew_caps = time_after_eq(jiffies, HZ*renew_interval +
@@ -3893,6 +3895,10 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
        ceph_caps_init(mdsc);
        ceph_adjust_min_caps(mdsc, fsc->min_caps);
 
+       spin_lock_init(&mdsc->snapid_map_lock);
+       mdsc->snapid_map_tree = RB_ROOT;
+       INIT_LIST_HEAD(&mdsc->snapid_map_lru);
+
        init_rwsem(&mdsc->pool_perm_rwsem);
        mdsc->pool_perm_tree = RB_ROOT;
 
@@ -4086,6 +4092,8 @@ void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
        WARN_ON(!list_empty(&mdsc->cap_delay_list));
        mutex_unlock(&mdsc->mutex);
 
+       ceph_cleanup_snapid_map(mdsc);
+
        ceph_cleanup_empty_realms(mdsc);
 
        cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */

diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 4f96264..d3a5c40 100644 (file)
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -313,6 +313,15 @@ struct ceph_pool_perm {
        char pool_ns[];
 };
 
+struct ceph_snapid_map {
+       struct rb_node node;
+       struct list_head lru;
+       atomic_t ref;
+       u64 snap;
+       dev_t dev;
+       unsigned long last_used;
+};
+
 /*
  * mds client state
  */
@@ -390,6 +399,10 @@ struct ceph_mds_client {
        struct list_head  dentry_lru;
        int               num_dentry;
 
+       spinlock_t              snapid_map_lock;
+       struct rb_root          snapid_map_tree;
+       struct list_head        snapid_map_lru;
+
        struct rw_semaphore     pool_perm_rwsem;
        struct rb_root          pool_perm_tree;
 

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index dfc25ce..89aa37f 100644 (file)
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -3,12 +3,13 @@
 
 #include <linux/sort.h>
 #include <linux/slab.h>
-
 #include "super.h"
 #include "mds_client.h"
-
 #include <linux/ceph/decode.h>
 
+/* unused map expires after 5 minutes */
+#define CEPH_SNAPID_MAP_TIMEOUT        (5 * 60 * HZ)
+
 /*
  * Snapshots in ceph are driven in large part by cooperation from the
  * client.  In contrast to local file systems or file servers that
@@ -989,3 +990,154 @@ out:
                up_write(&mdsc->snap_rwsem);
        return;
 }
+
+struct ceph_snapid_map* ceph_get_snapid_map(struct ceph_mds_client *mdsc,
+                                           u64 snap)
+{
+       struct ceph_snapid_map *sm, *exist;
+       struct rb_node **p, *parent;
+       int ret;
+
+       exist = NULL;
+       spin_lock(&mdsc->snapid_map_lock);
+       p = &mdsc->snapid_map_tree.rb_node;
+       while (*p) {
+               exist = rb_entry(*p, struct ceph_snapid_map, node);
+               if (snap > exist->snap) {
+                       p = &(*p)->rb_left;
+               } else if (snap < exist->snap) {
+                       p = &(*p)->rb_right;
+               } else {
+                       if (atomic_inc_return(&exist->ref) == 1)
+                               list_del_init(&exist->lru);
+                       break;
+               }
+               exist = NULL;
+       }
+       spin_unlock(&mdsc->snapid_map_lock);
+       if (exist) {
+               dout("found snapid map %llx -> %x\n", exist->snap, exist->dev);
+               return exist;
+       }
+
+       sm = kmalloc(sizeof(*sm), GFP_NOFS);
+       if (!sm)
+               return NULL;
+
+       ret = get_anon_bdev(&sm->dev);
+       if (ret < 0) {
+               kfree(sm);
+               return NULL;
+       }
+
+       INIT_LIST_HEAD(&sm->lru);
+       atomic_set(&sm->ref, 1);
+       sm->snap = snap;
+
+       exist = NULL;
+       parent = NULL;
+       p = &mdsc->snapid_map_tree.rb_node;
+       spin_lock(&mdsc->snapid_map_lock);
+       while (*p) {
+               parent = *p;
+               exist = rb_entry(*p, struct ceph_snapid_map, node);
+               if (snap > exist->snap)
+                       p = &(*p)->rb_left;
+               else if (snap < exist->snap)
+                       p = &(*p)->rb_right;
+               else
+                       break;
+               exist = NULL;
+       }
+       if (exist) {
+               if (atomic_inc_return(&exist->ref) == 1)
+                       list_del_init(&exist->lru);
+       } else {
+               rb_link_node(&sm->node, parent, p);
+               rb_insert_color(&sm->node, &mdsc->snapid_map_tree);
+       }
+       spin_unlock(&mdsc->snapid_map_lock);
+       if (exist) {
+               free_anon_bdev(sm->dev);
+               kfree(sm);
+               dout("found snapid map %llx -> %x\n", exist->snap, exist->dev);
+               return exist;
+       }
+
+       dout("create snapid map %llx -> %x\n", sm->snap, sm->dev);
+       return sm;
+}
+
+void ceph_put_snapid_map(struct ceph_mds_client* mdsc,
+                        struct ceph_snapid_map *sm)
+{
+       if (!sm)
+               return;
+       if (atomic_dec_and_lock(&sm->ref, &mdsc->snapid_map_lock)) {
+               if (!RB_EMPTY_NODE(&sm->node)) {
+                       sm->last_used = jiffies;
+                       list_add_tail(&sm->lru, &mdsc->snapid_map_lru);
+                       spin_unlock(&mdsc->snapid_map_lock);
+               } else {
+                       /* already cleaned up by
+                        * ceph_cleanup_snapid_map() */
+                       spin_unlock(&mdsc->snapid_map_lock);
+                       kfree(sm);
+               }
+       }
+}
+
+void ceph_trim_snapid_map(struct ceph_mds_client *mdsc)
+{
+       struct ceph_snapid_map *sm;
+       unsigned long now;
+       LIST_HEAD(to_free);
+
+       spin_lock(&mdsc->snapid_map_lock);
+       now = jiffies;
+
+       while (!list_empty(&mdsc->snapid_map_lru)) {
+               sm = list_first_entry(&mdsc->snapid_map_lru,
+                                     struct ceph_snapid_map, lru);
+               if (time_after(sm->last_used + CEPH_SNAPID_MAP_TIMEOUT, now))
+                       break;
+
+               rb_erase(&sm->node, &mdsc->snapid_map_tree);
+               list_move(&sm->lru, &to_free);
+       }
+       spin_unlock(&mdsc->snapid_map_lock);
+
+       while (!list_empty(&to_free)) {
+               sm = list_first_entry(&to_free, struct ceph_snapid_map, lru);
+               list_del(&sm->lru);
+               dout("trim snapid map %llx -> %x\n", sm->snap, sm->dev);
+               free_anon_bdev(sm->dev);
+               kfree(sm);
+       }
+}
+
+void ceph_cleanup_snapid_map(struct ceph_mds_client *mdsc)
+{
+       struct ceph_snapid_map *sm;
+       struct rb_node *p;
+       LIST_HEAD(to_free);
+
+       spin_lock(&mdsc->snapid_map_lock);
+       while ((p = rb_first(&mdsc->snapid_map_tree))) {
+               sm = rb_entry(p, struct ceph_snapid_map, node);
+               rb_erase(p, &mdsc->snapid_map_tree);
+               RB_CLEAR_NODE(p);
+               list_move(&sm->lru, &to_free);
+       }
+       spin_unlock(&mdsc->snapid_map_lock);
+
+       while (!list_empty(&to_free)) {
+               sm = list_first_entry(&to_free, struct ceph_snapid_map, lru);
+               list_del(&sm->lru);
+               free_anon_bdev(sm->dev);
+               if (WARN_ON_ONCE(atomic_read(&sm->ref))) {
+                       pr_err("snapid map %llx -> %x still in use\n",
+                              sm->snap, sm->dev);
+               }
+       }
+}

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index dfb64a5..5b15ae9 100644 (file)
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -370,7 +370,10 @@ struct ceph_inode_info {
        struct list_head i_unsafe_iops;   /* uncommitted mds inode ops */
        spinlock_t i_unsafe_lock;
 
-       struct ceph_snap_realm *i_snap_realm; /* snap realm (if caps) */
+       union {
+               struct ceph_snap_realm *i_snap_realm; /* snap realm (if caps) */
+               struct ceph_snapid_map *i_snapid_map; /* snapid -> dev_t */
+       };
        int i_snap_realm_counter; /* snap realm (if caps) */
        struct list_head i_snap_realm_item;
        struct list_head i_snap_flush_item;
@@ -837,6 +840,14 @@ extern int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
                                  struct ceph_cap_snap *capsnap);
 extern void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc);
 
+extern struct ceph_snapid_map *ceph_get_snapid_map(struct ceph_mds_client *mdsc,
+                                                  u64 snap);
+extern void ceph_put_snapid_map(struct ceph_mds_client* mdsc,
+                               struct ceph_snapid_map *sm);
+extern void ceph_trim_snapid_map(struct ceph_mds_client *mdsc);
+extern void ceph_cleanup_snapid_map(struct ceph_mds_client *mdsc);
+
+
 /*
  * a cap_snap is "pending" if it is still awaiting an in-progress
  * sync write (that may/may not still update size, mtime, etc.).