1 files changed, 632 insertions, 221 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index f01645a27752..c65f2b202b2b 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -1,13 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/ceph/ceph_debug.h>
 
+#include <linux/fs.h>
 #include <linux/sort.h>
 #include <linux/slab.h>
-
+#include <linux/iversion.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
@@ -57,26 +61,26 @@
 /*
  * increase ref count for the realm
  *
- * caller must hold snap_rwsem for write.
+ * caller must hold snap_rwsem.
  */
 void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
 			 struct ceph_snap_realm *realm)
 {
-	dout("get_realm %p %d -> %d\n", realm,
-	     atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
+	lockdep_assert_held(&mdsc->snap_rwsem);
+
 	/*
-	 * since we _only_ increment realm refs or empty the empty
-	 * list with snap_rwsem held, adjusting the empty list here is
-	 * safe.  we do need to protect against concurrent empty list
-	 * additions, however.
+	 * The 0->1 and 1->0 transitions must take the snap_empty_lock
+	 * atomically with the refcount change. Go ahead and bump the
+	 * nref here, unless it's 0, in which case we take the spinlock
+	 * and then do the increment and remove it from the list.
 	 */
-	if (atomic_read(&realm->nref) == 0) {
-		spin_lock(&mdsc->snap_empty_lock);
-		list_del_init(&realm->empty_item);
-		spin_unlock(&mdsc->snap_empty_lock);
-	}
+	if (atomic_inc_not_zero(&realm->nref))
+		return;
 
-	atomic_inc(&realm->nref);
+	spin_lock(&mdsc->snap_empty_lock);
+	if (atomic_inc_return(&realm->nref) == 1)
+		list_del_init(&realm->empty_item);
+	spin_unlock(&mdsc->snap_empty_lock);
 }
 
 static void __insert_snap_realm(struct rb_root *root,
@@ -112,34 +116,46 @@ static struct ceph_snap_realm *ceph_create_snap_realm(
 {
 	struct ceph_snap_realm *realm;
 
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
 	realm = kzalloc(sizeof(*realm), GFP_NOFS);
 	if (!realm)
 		return ERR_PTR(-ENOMEM);
 
-	atomic_set(&realm->nref, 0);    /* tree does not take a ref */
+	/* Do not release the global dummy snaprealm until unmouting */
+	if (ino == CEPH_INO_GLOBAL_SNAPREALM)
+		atomic_set(&realm->nref, 2);
+	else
+		atomic_set(&realm->nref, 1);
 	realm->ino = ino;
 	INIT_LIST_HEAD(&realm->children);
 	INIT_LIST_HEAD(&realm->child_item);
 	INIT_LIST_HEAD(&realm->empty_item);
 	INIT_LIST_HEAD(&realm->dirty_item);
+	INIT_LIST_HEAD(&realm->rebuild_item);
 	INIT_LIST_HEAD(&realm->inodes_with_caps);
 	spin_lock_init(&realm->inodes_with_caps_lock);
 	__insert_snap_realm(&mdsc->snap_realms, realm);
-	dout("create_snap_realm %llx %p\n", realm->ino, realm);
+	mdsc->num_snap_realms++;
+
+	doutc(mdsc->fsc->client, "%llx %p\n", realm->ino, realm);
 	return realm;
 }
 
 /*
  * lookup the realm rooted at @ino.
  *
- * caller must hold snap_rwsem for write.
+ * caller must hold snap_rwsem.
  */
-struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
-					       u64 ino)
+static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
+						   u64 ino)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct rb_node *n = mdsc->snap_realms.rb_node;
 	struct ceph_snap_realm *r;
 
+	lockdep_assert_held(&mdsc->snap_rwsem);
+
 	while (n) {
 		r = rb_entry(n, struct ceph_snap_realm, node);
 		if (ino < r->ino)
@@ -147,13 +163,23 @@ struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
 		else if (ino > r->ino)
 			n = n->rb_right;
 		else {
-			dout("lookup_snap_realm %llx %p\n", r->ino, r);
+			doutc(cl, "%llx %p\n", r->ino, r);
 			return r;
 		}
 	}
 	return NULL;
 }
 
+struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
+					       u64 ino)
+{
+	struct ceph_snap_realm *r;
+	r = __lookup_snap_realm(mdsc, ino);
+	if (r)
+		ceph_get_snap_realm(mdsc, r);
+	return r;
+}
+
 static void __put_snap_realm(struct ceph_mds_client *mdsc,
 			     struct ceph_snap_realm *realm);
 
@@ -163,9 +189,13 @@ static void __put_snap_realm(struct ceph_mds_client *mdsc,
 static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
 				 struct ceph_snap_realm *realm)
 {
-	dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
+	struct ceph_client *cl = mdsc->fsc->client;
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
+	doutc(cl, "%p %llx\n", realm, realm->ino);
 
 	rb_erase(&realm->node, &mdsc->snap_realms);
+	mdsc->num_snap_realms--;
 
 	if (realm->parent) {
 		list_del_init(&realm->child_item);
@@ -184,28 +214,30 @@ static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
 static void __put_snap_realm(struct ceph_mds_client *mdsc,
 			     struct ceph_snap_realm *realm)
 {
-	dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
-	     atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
+	/*
+	 * We do not require the snap_empty_lock here, as any caller that
+	 * increments the value must hold the snap_rwsem.
+	 */
 	if (atomic_dec_and_test(&realm->nref))
 		__destroy_snap_realm(mdsc, realm);
 }
 
 /*
- * caller needn't hold any locks
+ * See comments in ceph_get_snap_realm. Caller needn't hold any locks.
  */
 void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
 			 struct ceph_snap_realm *realm)
 {
-	dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
-	     atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
-	if (!atomic_dec_and_test(&realm->nref))
+	if (!atomic_dec_and_lock(&realm->nref, &mdsc->snap_empty_lock))
 		return;
 
 	if (down_write_trylock(&mdsc->snap_rwsem)) {
+		spin_unlock(&mdsc->snap_empty_lock);
 		__destroy_snap_realm(mdsc, realm);
 		up_write(&mdsc->snap_rwsem);
 	} else {
-		spin_lock(&mdsc->snap_empty_lock);
 		list_add(&realm->empty_item, &mdsc->snap_empty);
 		spin_unlock(&mdsc->snap_empty_lock);
 	}
@@ -222,6 +254,8 @@ static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
 {
 	struct ceph_snap_realm *realm;
 
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
 	spin_lock(&mdsc->snap_empty_lock);
 	while (!list_empty(&mdsc->snap_empty)) {
 		realm = list_first_entry(&mdsc->snap_empty,
@@ -234,9 +268,14 @@ static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
 	spin_unlock(&mdsc->snap_empty_lock);
 }
 
-void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
+void ceph_cleanup_global_and_empty_realms(struct ceph_mds_client *mdsc)
 {
+	struct ceph_snap_realm *global_realm;
+
 	down_write(&mdsc->snap_rwsem);
+	global_realm = __lookup_snap_realm(mdsc, CEPH_INO_GLOBAL_SNAPREALM);
+	if (global_realm)
+		ceph_put_snap_realm(mdsc, global_realm);
 	__cleanup_empty_realms(mdsc);
 	up_write(&mdsc->snap_rwsem);
 }
@@ -253,8 +292,11 @@ static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
 				    struct ceph_snap_realm *realm,
 				    u64 parentino)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_snap_realm *parent;
 
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
 	if (realm->parent_ino == parentino)
 		return 0;
 
@@ -264,16 +306,14 @@ static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
 		if (IS_ERR(parent))
 			return PTR_ERR(parent);
 	}
-	dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
-	     realm->ino, realm, realm->parent_ino, realm->parent,
-	     parentino, parent);
+	doutc(cl, "%llx %p: %llx %p -> %llx %p\n", realm->ino, realm,
+	      realm->parent_ino, realm->parent, parentino, parent);
 	if (realm->parent) {
 		list_del_init(&realm->child_item);
 		ceph_put_snap_realm(mdsc, realm->parent);
 	}
 	realm->parent_ino = parentino;
 	realm->parent = parent;
-	ceph_get_snap_realm(mdsc, parent);
 	list_add(&realm->child_item, &parent->children);
 	return 1;
 }
@@ -288,11 +328,16 @@ static int cmpu64_rev(const void *a, const void *b)
 	return 0;
 }
 
+
 /*
  * build the snap context for a given realm.
  */
-static int build_snap_context(struct ceph_snap_realm *realm)
+static int build_snap_context(struct ceph_mds_client *mdsc,
+			      struct ceph_snap_realm *realm,
+			      struct list_head *realm_queue,
+			      struct list_head *dirty_realms)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_snap_realm *parent = realm->parent;
 	struct ceph_snap_context *snapc;
 	int err = 0;
@@ -305,9 +350,9 @@ static int build_snap_context(struct ceph_snap_realm *realm)
 	 */
 	if (parent) {
 		if (!parent->cached_context) {
-			err = build_snap_context(parent);
-			if (err)
-				goto fail;
+			/* add to the queue head */
+			list_add(&parent->rebuild_item, realm_queue);
+			return 1;
 		}
 		num += parent->cached_context->num_snaps;
 	}
@@ -320,11 +365,10 @@ static int build_snap_context(struct ceph_snap_realm *realm)
 	    realm->cached_context->seq == realm->seq &&
 	    (!parent ||
 	     realm->cached_context->seq >= parent->cached_context->seq)) {
-		dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
-		     " (unchanged)\n",
-		     realm->ino, realm, realm->cached_context,
-		     realm->cached_context->seq,
-		     (unsigned int) realm->cached_context->num_snaps);
+		doutc(cl, "%llx %p: %p seq %lld (%u snaps) (unchanged)\n",
+		      realm->ino, realm, realm->cached_context,
+		      realm->cached_context->seq,
+		      (unsigned int)realm->cached_context->num_snaps);
 		return 0;
 	}
 
@@ -361,13 +405,13 @@ static int build_snap_context(struct ceph_snap_realm *realm)
 
 	sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
 	snapc->num_snaps = num;
-	dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
-	     realm->ino, realm, snapc, snapc->seq,
-	     (unsigned int) snapc->num_snaps);
+	doutc(cl, "%llx %p: %p seq %lld (%u snaps)\n", realm->ino, realm,
+	      snapc, snapc->seq, (unsigned int) snapc->num_snaps);
 
-	if (realm->cached_context)
-		ceph_put_snap_context(realm->cached_context);
+	ceph_put_snap_context(realm->cached_context);
 	realm->cached_context = snapc;
+	/* queue realm for cap_snap creation */
+	list_add_tail(&realm->dirty_item, dirty_realms);
 	return 0;
 
 fail:
@@ -379,23 +423,63 @@ fail:
 		ceph_put_snap_context(realm->cached_context);
 		realm->cached_context = NULL;
 	}
-	pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
-	       realm, err);
+	pr_err_client(cl, "%llx %p fail %d\n", realm->ino, realm, err);
 	return err;
 }
 
 /*
  * rebuild snap context for the given realm and all of its children.
  */
-static void rebuild_snap_realms(struct ceph_snap_realm *realm)
+static void rebuild_snap_realms(struct ceph_mds_client *mdsc,
+				struct ceph_snap_realm *realm,
+				struct list_head *dirty_realms)
 {
-	struct ceph_snap_realm *child;
+	struct ceph_client *cl = mdsc->fsc->client;
+	LIST_HEAD(realm_queue);
+	int last = 0;
+	bool skip = false;
+
+	list_add_tail(&realm->rebuild_item, &realm_queue);
+
+	while (!list_empty(&realm_queue)) {
+		struct ceph_snap_realm *_realm, *child;
+
+		_realm = list_first_entry(&realm_queue,
+					  struct ceph_snap_realm,
+					  rebuild_item);
+
+		/*
+		 * If the last building failed dues to memory
+		 * issue, just empty the realm_queue and return
+		 * to avoid infinite loop.
+		 */
+		if (last < 0) {
+			list_del_init(&_realm->rebuild_item);
+			continue;
+		}
 
-	dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
-	build_snap_context(realm);
+		last = build_snap_context(mdsc, _realm, &realm_queue,
+					  dirty_realms);
+		doutc(cl, "%llx %p, %s\n", realm->ino, realm,
+		      last > 0 ? "is deferred" : !last ? "succeeded" : "failed");
 
-	list_for_each_entry(child, &realm->children, child_item)
-		rebuild_snap_realms(child);
+		/* is any child in the list ? */
+		list_for_each_entry(child, &_realm->children, child_item) {
+			if (!list_empty(&child->rebuild_item)) {
+				skip = true;
+				break;
+			}
+		}
+
+		if (!skip) {
+			list_for_each_entry(child, &_realm->children, child_item)
+				list_add_tail(&child->rebuild_item, &realm_queue);
+		}
+
+		/* last == 1 means need to build parent first */
+		if (last <= 0)
+			list_del_init(&_realm->rebuild_item);
+	}
 }
 
 
@@ -420,6 +504,14 @@ static int dup_array(u64 **dst, __le64 *src, u32 num)
 	return 0;
 }
 
+static bool has_new_snaps(struct ceph_snap_context *o,
+			  struct ceph_snap_context *n)
+{
+	if (n->num_snaps == 0)
+		return false;
+	/* snaps are in descending order */
+	return n->snaps[0] > o->seq;
+}
 
 /*
  * When a snapshot is applied, the size/mtime inode metadata is queued
@@ -435,22 +527,23 @@ static int dup_array(u64 **dst, __le64 *src, u32 num)
  * Caller must hold snap_rwsem for read (i.e., the realm topology won't
  * change).
  */
-void ceph_queue_cap_snap(struct ceph_inode_info *ci)
+static void ceph_queue_cap_snap(struct ceph_inode_info *ci,
+				struct ceph_cap_snap **pcapsnap)
 {
-	struct inode *inode = &ci->vfs_inode;
-	struct ceph_cap_snap *capsnap;
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_client *cl = ceph_inode_to_client(inode);
+	struct ceph_snap_context *old_snapc, *new_snapc;
+	struct ceph_cap_snap *capsnap = *pcapsnap;
+	struct ceph_buffer *old_blob = NULL;
 	int used, dirty;
 
-	capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
-	if (!capsnap) {
-		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
-		return;
-	}
-
 	spin_lock(&ci->i_ceph_lock);
 	used = __ceph_caps_used(ci);
 	dirty = __ceph_caps_dirty(ci);
 
+	old_snapc = ci->i_head_snapc;
+	new_snapc = ci->i_snap_realm->cached_context;
+
 	/*
 	 * If there is a write in progress, treat that as a dirty Fw,
 	 * even though it hasn't completed yet; by the time we finish
@@ -464,72 +557,98 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci)
 		   as no new writes are allowed to start when pending, so any
 		   writes in progress now were started before the previous
 		   cap_snap.  lucky us. */
-		dout("queue_cap_snap %p already pending\n", inode);
-		kfree(capsnap);
-	} else if (dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL|
-			    CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR)) {
-		struct ceph_snap_context *snapc = ci->i_head_snapc;
-
-		/*
-		 * if we are a sync write, we may need to go to the snaprealm
-		 * to get the current snapc.
-		 */
-		if (!snapc)
-			snapc = ci->i_snap_realm->cached_context;
+		doutc(cl, "%p %llx.%llx already pending\n", inode,
+		      ceph_vinop(inode));
+		goto update_snapc;
+	}
+	if (ci->i_wrbuffer_ref_head == 0 &&
+	    !(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {
+		doutc(cl, "%p %llx.%llx nothing dirty|writing\n", inode,
+		      ceph_vinop(inode));
+		goto update_snapc;
+	}
 
-		dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n",
-		     inode, capsnap, snapc, ceph_cap_string(dirty));
-		ihold(inode);
+	BUG_ON(!old_snapc);
 
-		atomic_set(&capsnap->nref, 1);
-		capsnap->ci = ci;
-		INIT_LIST_HEAD(&capsnap->ci_item);
-		INIT_LIST_HEAD(&capsnap->flushing_item);
+	/*
+	 * There is no need to send FLUSHSNAP message to MDS if there is
+	 * no new snapshot. But when there is dirty pages or on-going
+	 * writes, we still need to create cap_snap. cap_snap is needed
+	 * by the write path and page writeback path.
+	 *
+	 * also see ceph_try_drop_cap_snap()
+	 */
+	if (has_new_snaps(old_snapc, new_snapc)) {
+		if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))
+			capsnap->need_flush = true;
+	} else {
+		if (!(used & CEPH_CAP_FILE_WR) &&
+		    ci->i_wrbuffer_ref_head == 0) {
+			doutc(cl, "%p %llx.%llx no new_snap|dirty_page|writing\n",
+			      inode, ceph_vinop(inode));
+			goto update_snapc;
+		}
+	}
 
-		capsnap->follows = snapc->seq;
-		capsnap->issued = __ceph_caps_issued(ci, NULL);
-		capsnap->dirty = dirty;
+	doutc(cl, "%p %llx.%llx cap_snap %p queuing under %p %s %s\n",
+	      inode, ceph_vinop(inode), capsnap, old_snapc,
+	      ceph_cap_string(dirty), capsnap->need_flush ? "" : "no_flush");
+	ihold(inode);
 
-		capsnap->mode = inode->i_mode;
-		capsnap->uid = inode->i_uid;
-		capsnap->gid = inode->i_gid;
+	capsnap->follows = old_snapc->seq;
+	capsnap->issued = __ceph_caps_issued(ci, NULL);
+	capsnap->dirty = dirty;
 
-		if (dirty & CEPH_CAP_XATTR_EXCL) {
-			__ceph_build_xattrs_blob(ci);
-			capsnap->xattr_blob =
-				ceph_buffer_get(ci->i_xattrs.blob);
-			capsnap->xattr_version = ci->i_xattrs.version;
-		} else {
-			capsnap->xattr_blob = NULL;
-			capsnap->xattr_version = 0;
-		}
+	capsnap->mode = inode->i_mode;
+	capsnap->uid = inode->i_uid;
+	capsnap->gid = inode->i_gid;
 
-		/* dirty page count moved from _head to this cap_snap;
-		   all subsequent writes page dirties occur _after_ this
-		   snapshot. */
-		capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
-		ci->i_wrbuffer_ref_head = 0;
-		capsnap->context = snapc;
-		ci->i_head_snapc =
-			ceph_get_snap_context(ci->i_snap_realm->cached_context);
-		dout(" new snapc is %p\n", ci->i_head_snapc);
-		list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
-
-		if (used & CEPH_CAP_FILE_WR) {
-			dout("queue_cap_snap %p cap_snap %p snapc %p"
-			     " seq %llu used WR, now pending\n", inode,
-			     capsnap, snapc, snapc->seq);
-			capsnap->writing = 1;
-		} else {
-			/* note mtime, size NOW. */
-			__ceph_finish_cap_snap(ci, capsnap);
-		}
+	if (dirty & CEPH_CAP_XATTR_EXCL) {
+		old_blob = __ceph_build_xattrs_blob(ci);
+		capsnap->xattr_blob =
+			ceph_buffer_get(ci->i_xattrs.blob);
+		capsnap->xattr_version = ci->i_xattrs.version;
 	} else {
-		dout("queue_cap_snap %p nothing dirty|writing\n", inode);
-		kfree(capsnap);
+		capsnap->xattr_blob = NULL;
+		capsnap->xattr_version = 0;
 	}
 
+	capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;
+
+	/* dirty page count moved from _head to this cap_snap;
+	   all subsequent writes page dirties occur _after_ this
+	   snapshot. */
+	capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
+	ci->i_wrbuffer_ref_head = 0;
+	capsnap->context = old_snapc;
+	list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
+
+	if (used & CEPH_CAP_FILE_WR) {
+		doutc(cl, "%p %llx.%llx cap_snap %p snapc %p seq %llu used WR,"
+		      " now pending\n", inode, ceph_vinop(inode), capsnap,
+		      old_snapc, old_snapc->seq);
+		capsnap->writing = 1;
+	} else {
+		/* note mtime, size NOW. */
+		__ceph_finish_cap_snap(ci, capsnap);
+	}
+	*pcapsnap = NULL;
+	old_snapc = NULL;
+
+update_snapc:
+	if (ci->i_wrbuffer_ref_head == 0 &&
+	    ci->i_wr_ref == 0 &&
+	    ci->i_dirty_caps == 0 &&
+	    ci->i_flushing_caps == 0) {
+		ci->i_head_snapc = NULL;
+	} else {
+		ci->i_head_snapc = ceph_get_snap_context(new_snapc);
+		doutc(cl, " new snapc is %p\n", new_snapc);
+	}
 	spin_unlock(&ci->i_ceph_lock);
+
+	ceph_buffer_put(old_blob);
+	ceph_put_snap_context(old_snapc);
 }
 
 /*
@@ -543,30 +662,55 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci)
 int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
 			    struct ceph_cap_snap *capsnap)
 {
-	struct inode *inode = &ci->vfs_inode;
-	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
+	struct ceph_client *cl = mdsc->fsc->client;
 
 	BUG_ON(capsnap->writing);
-	capsnap->size = inode->i_size;
-	capsnap->mtime = inode->i_mtime;
-	capsnap->atime = inode->i_atime;
-	capsnap->ctime = inode->i_ctime;
+	capsnap->size = i_size_read(inode);
+	capsnap->mtime = inode_get_mtime(inode);
+	capsnap->atime = inode_get_atime(inode);
+	capsnap->ctime = inode_get_ctime(inode);
+	capsnap->btime = ci->i_btime;
+	capsnap->change_attr = inode_peek_iversion_raw(inode);
 	capsnap->time_warp_seq = ci->i_time_warp_seq;
+	capsnap->truncate_size = ci->i_truncate_size;
+	capsnap->truncate_seq = ci->i_truncate_seq;
 	if (capsnap->dirty_pages) {
-		dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
-		     "still has %d dirty pages\n", inode, capsnap,
-		     capsnap->context, capsnap->context->seq,
-		     ceph_cap_string(capsnap->dirty), capsnap->size,
-		     capsnap->dirty_pages);
+		doutc(cl, "%p %llx.%llx cap_snap %p snapc %p %llu %s "
+		      "s=%llu still has %d dirty pages\n", inode,
+		      ceph_vinop(inode), capsnap, capsnap->context,
+		      capsnap->context->seq,
+		      ceph_cap_string(capsnap->dirty),
+		      capsnap->size, capsnap->dirty_pages);
+		return 0;
+	}
+
+	/*
+	 * Defer flushing the capsnap if the dirty buffer not flushed yet.
+	 * And trigger to flush the buffer immediately.
+	 */
+	if (ci->i_wrbuffer_ref) {
+		doutc(cl, "%p %llx.%llx cap_snap %p snapc %p %llu %s "
+		      "s=%llu used WRBUFFER, delaying\n", inode,
+		      ceph_vinop(inode), capsnap, capsnap->context,
+		      capsnap->context->seq, ceph_cap_string(capsnap->dirty),
+		      capsnap->size);
+		ceph_queue_writeback(inode);
 		return 0;
 	}
-	dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
-	     inode, capsnap, capsnap->context,
-	     capsnap->context->seq, ceph_cap_string(capsnap->dirty),
-	     capsnap->size);
+
+	ci->i_ceph_flags |= CEPH_I_FLUSH_SNAPS;
+	doutc(cl, "%p %llx.%llx cap_snap %p snapc %p %llu %s s=%llu\n",
+	      inode, ceph_vinop(inode), capsnap, capsnap->context,
+	      capsnap->context->seq, ceph_cap_string(capsnap->dirty),
+	      capsnap->size);
 
 	spin_lock(&mdsc->snap_flush_lock);
-	list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
+	if (list_empty(&ci->i_snap_flush_item)) {
+		ihold(inode);
+		list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
+	}
 	spin_unlock(&mdsc->snap_flush_lock);
 	return 1;  /* caller may want to ceph_flush_snaps */
 }
@@ -575,40 +719,54 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
  * Queue cap_snaps for snap writeback for this realm and its children.
  * Called under snap_rwsem, so realm topology won't change.
  */
-static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
+static void queue_realm_cap_snaps(struct ceph_mds_client *mdsc,
+				  struct ceph_snap_realm *realm)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_inode_info *ci;
 	struct inode *lastinode = NULL;
-	struct ceph_snap_realm *child;
+	struct ceph_cap_snap *capsnap = NULL;
 
-	dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
+	doutc(cl, "%p %llx inode\n", realm, realm->ino);
 
 	spin_lock(&realm->inodes_with_caps_lock);
-	list_for_each_entry(ci, &realm->inodes_with_caps,
-			    i_snap_realm_item) {
-		struct inode *inode = igrab(&ci->vfs_inode);
+	list_for_each_entry(ci, &realm->inodes_with_caps, i_snap_realm_item) {
+		struct inode *inode = igrab(&ci->netfs.inode);
 		if (!inode)
 			continue;
 		spin_unlock(&realm->inodes_with_caps_lock);
-		if (lastinode)
-			iput(lastinode);
+		iput(lastinode);
 		lastinode = inode;
-		ceph_queue_cap_snap(ci);
+
+		/*
+		 * Allocate the capsnap memory outside of ceph_queue_cap_snap()
+		 * to reduce very possible but unnecessary frequently memory
+		 * allocate/free in this loop.
+		 */
+		if (!capsnap) {
+			capsnap = kmem_cache_zalloc(ceph_cap_snap_cachep, GFP_NOFS);
+			if (!capsnap) {
+				pr_err_client(cl,
+					"ENOMEM allocating ceph_cap_snap on %p\n",
+					inode);
+				return;
+			}
+		}
+		capsnap->cap_flush.is_capsnap = true;
+		refcount_set(&capsnap->nref, 1);
+		INIT_LIST_HEAD(&capsnap->cap_flush.i_list);
+		INIT_LIST_HEAD(&capsnap->cap_flush.g_list);
+		INIT_LIST_HEAD(&capsnap->ci_item);
+
+		ceph_queue_cap_snap(ci, &capsnap);
 		spin_lock(&realm->inodes_with_caps_lock);
 	}
 	spin_unlock(&realm->inodes_with_caps_lock);
-	if (lastinode)
-		iput(lastinode);
-
-	list_for_each_entry(child, &realm->children, child_item) {
-		dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
-		     realm, realm->ino, child, child->ino);
-		list_del_init(&child->dirty_item);
-		list_add(&child->dirty_item, &realm->dirty_item);
-	}
+	iput(lastinode);
 
-	list_del_init(&realm->dirty_item);
-	dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
+	if (capsnap)
+		kmem_cache_free(ceph_cap_snap_cachep, capsnap);
+	doutc(cl, "%p %llx done\n", realm, realm->ino);
 }
 
 /*
@@ -619,18 +777,28 @@ static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
  * Caller must hold snap_rwsem for write.
  */
 int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
-			   void *p, void *e, bool deletion)
+			   void *p, void *e, bool deletion,
+			   struct ceph_snap_realm **realm_ret)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_mds_snap_realm *ri;    /* encoded */
 	__le64 *snaps;                     /* encoded */
 	__le64 *prior_parent_snaps;        /* encoded */
 	struct ceph_snap_realm *realm;
-	int invalidate = 0;
+	struct ceph_snap_realm *first_realm = NULL;
+	struct ceph_snap_realm *realm_to_rebuild = NULL;
+	struct ceph_client *client = mdsc->fsc->client;
+	int rebuild_snapcs;
 	int err = -ENOMEM;
+	int ret;
 	LIST_HEAD(dirty_realms);
 
-	dout("update_snap_trace deletion=%d\n", deletion);
+	lockdep_assert_held_write(&mdsc->snap_rwsem);
+
+	doutc(cl, "deletion=%d\n", deletion);
 more:
+	realm = NULL;
+	rebuild_snapcs = 0;
 	ceph_decode_need(&p, e, sizeof(*ri), bad);
 	ri = p;
 	p += sizeof(*ri);
@@ -654,11 +822,11 @@ more:
 	err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
 	if (err < 0)
 		goto fail;
-	invalidate += err;
+	rebuild_snapcs += err;
 
 	if (le64_to_cpu(ri->seq) > realm->seq) {
-		dout("update_snap_trace updating %llx %p %lld -> %lld\n",
-		     realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
+		doutc(cl, "updating %llx %p %lld -> %lld\n", realm->ino,
+		      realm, realm->seq, le64_to_cpu(ri->seq));
 		/* update realm parameters, snap lists */
 		realm->seq = le64_to_cpu(ri->seq);
 		realm->created = le64_to_cpu(ri->created);
@@ -676,29 +844,42 @@ more:
 		if (err < 0)
 			goto fail;
 
-		/* queue realm for cap_snap creation */
-		list_add(&realm->dirty_item, &dirty_realms);
+		if (realm->seq > mdsc->last_snap_seq)
+			mdsc->last_snap_seq = realm->seq;
 
-		invalidate = 1;
+		rebuild_snapcs = 1;
 	} else if (!realm->cached_context) {
-		dout("update_snap_trace %llx %p seq %lld new\n",
-		     realm->ino, realm, realm->seq);
-		invalidate = 1;
+		doutc(cl, "%llx %p seq %lld new\n", realm->ino, realm,
+		      realm->seq);
+		rebuild_snapcs = 1;
 	} else {
-		dout("update_snap_trace %llx %p seq %lld unchanged\n",
-		     realm->ino, realm, realm->seq);
+		doutc(cl, "%llx %p seq %lld unchanged\n", realm->ino, realm,
+		      realm->seq);
 	}
 
-	dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
-	     realm, invalidate, p, e);
+	doutc(cl, "done with %llx %p, rebuild_snapcs=%d, %p %p\n", realm->ino,
+	      realm, rebuild_snapcs, p, e);
+
+	/*
+	 * this will always track the uppest parent realm from which
+	 * we need to rebuild the snapshot contexts _downward_ in
+	 * hierarchy.
+	 */
+	if (rebuild_snapcs)
+		realm_to_rebuild = realm;
+
+	/* rebuild_snapcs when we reach the _end_ (root) of the trace */
+	if (realm_to_rebuild && p >= e)
+		rebuild_snap_realms(mdsc, realm_to_rebuild, &dirty_realms);
+
+	if (!first_realm)
+		first_realm = realm;
+	else
+		ceph_put_snap_realm(mdsc, realm);
 
 	if (p < e)
 		goto more;
 
-	/* invalidate when we reach the _end_ (root) of the trace */
-	if (invalidate)
-		rebuild_snap_realms(realm);
-
 	/*
 	 * queue cap snaps _after_ we've built the new snap contexts,
 	 * so that i_head_snapc can be set appropriately.
@@ -706,16 +887,48 @@ more:
 	while (!list_empty(&dirty_realms)) {
 		realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
 					 dirty_item);
-		queue_realm_cap_snaps(realm);
+		list_del_init(&realm->dirty_item);
+		queue_realm_cap_snaps(mdsc, realm);
 	}
 
+	if (realm_ret)
+		*realm_ret = first_realm;
+	else
+		ceph_put_snap_realm(mdsc, first_realm);
+
 	__cleanup_empty_realms(mdsc);
 	return 0;
 
 bad:
-	err = -EINVAL;
+	err = -EIO;
 fail:
-	pr_err("update_snap_trace error %d\n", err);
+	if (realm && !IS_ERR(realm))
+		ceph_put_snap_realm(mdsc, realm);
+	if (first_realm)
+		ceph_put_snap_realm(mdsc, first_realm);
+	pr_err_client(cl, "error %d\n", err);
+
+	/*
+	 * When receiving a corrupted snap trace we don't know what
+	 * exactly has happened in MDS side. And we shouldn't continue
+	 * writing to OSD, which may corrupt the snapshot contents.
+	 *
+	 * Just try to blocklist this kclient and then this kclient
+	 * must be remounted to continue after the corrupted metadata
+	 * fixed in the MDS side.
+	 */
+	WRITE_ONCE(mdsc->fsc->mount_state, CEPH_MOUNT_FENCE_IO);
+	ret = ceph_monc_blocklist_add(&client->monc, &client->msgr.inst.addr);
+	if (ret)
+		pr_err_client(cl, "failed to blocklist %s: %d\n",
+			      ceph_pr_addr(&client->msgr.inst.addr), ret);
+
+	WARN(1, "[client.%lld] %s %s%sdo remount to continue%s",
+	     client->monc.auth->global_id, __func__,
+	     ret ? "" : ceph_pr_addr(&client->msgr.inst.addr),
+	     ret ? "" : " was blocklisted, ",
+	     err == -EIO ? " after corrupted snaptrace is fixed" : "");
+
 	return err;
 }
 
@@ -728,33 +941,66 @@ fail:
  */
 static void flush_snaps(struct ceph_mds_client *mdsc)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct ceph_inode_info *ci;
 	struct inode *inode;
 	struct ceph_mds_session *session = NULL;
 
-	dout("flush_snaps\n");
+	doutc(cl, "begin\n");
 	spin_lock(&mdsc->snap_flush_lock);
 	while (!list_empty(&mdsc->snap_flush_list)) {
 		ci = list_first_entry(&mdsc->snap_flush_list,
 				struct ceph_inode_info, i_snap_flush_item);
-		inode = &ci->vfs_inode;
+		inode = &ci->netfs.inode;
 		ihold(inode);
 		spin_unlock(&mdsc->snap_flush_lock);
-		spin_lock(&ci->i_ceph_lock);
-		__ceph_flush_snaps(ci, &session, 0);
-		spin_unlock(&ci->i_ceph_lock);
+		ceph_flush_snaps(ci, &session);
 		iput(inode);
 		spin_lock(&mdsc->snap_flush_lock);
 	}
 	spin_unlock(&mdsc->snap_flush_lock);
 
-	if (session) {
-		mutex_unlock(&session->s_mutex);
-		ceph_put_mds_session(session);
-	}
-	dout("flush_snaps done\n");
+	ceph_put_mds_session(session);
+	doutc(cl, "done\n");
 }
 
+/**
+ * ceph_change_snap_realm - change the snap_realm for an inode
+ * @inode: inode to move to new snap realm
+ * @realm: new realm to move inode into (may be NULL)
+ *
+ * Detach an inode from its old snaprealm (if any) and attach it to
+ * the new snaprealm (if any). The old snap realm reference held by
+ * the inode is put. If realm is non-NULL, then the caller's reference
+ * to it is taken over by the inode.
+ */
+void ceph_change_snap_realm(struct inode *inode, struct ceph_snap_realm *realm)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_inode_to_fs_client(inode)->mdsc;
+	struct ceph_snap_realm *oldrealm = ci->i_snap_realm;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	if (oldrealm) {
+		spin_lock(&oldrealm->inodes_with_caps_lock);
+		list_del_init(&ci->i_snap_realm_item);
+		if (oldrealm->ino == ci->i_vino.ino)
+			oldrealm->inode = NULL;
+		spin_unlock(&oldrealm->inodes_with_caps_lock);
+		ceph_put_snap_realm(mdsc, oldrealm);
+	}
+
+	ci->i_snap_realm = realm;
+
+	if (realm) {
+		spin_lock(&realm->inodes_with_caps_lock);
+		list_add(&ci->i_snap_realm_item, &realm->inodes_with_caps);
+		if (realm->ino == ci->i_vino.ino)
+			realm->inode = inode;
+		spin_unlock(&realm->inodes_with_caps_lock);
+	}
+}
 
 /*
  * Handle a snap notification from the MDS.
@@ -771,6 +1017,7 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 		      struct ceph_mds_session *session,
 		      struct ceph_msg *msg)
 {
+	struct ceph_client *cl = mdsc->fsc->client;
 	struct super_block *sb = mdsc->fsc->sb;
 	int mds = session->s_mds;
 	u64 split;
@@ -784,6 +1031,10 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 	__le64 *split_inos = NULL, *split_realms = NULL;
 	int i;
 	int locked_rwsem = 0;
+	bool close_sessions = false;
+
+	if (!ceph_inc_mds_stopping_blocker(mdsc, session))
+		return;
 
 	/* decode */
 	if (msg->front.iov_len < sizeof(*h))
@@ -797,12 +1048,8 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 	trace_len = le32_to_cpu(h->trace_len);
 	p += sizeof(*h);
 
-	dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
-	     ceph_snap_op_name(op), split, trace_len);
-
-	mutex_lock(&session->s_mutex);
-	session->s_seq++;
-	mutex_unlock(&session->s_mutex);
+	doutc(cl, "from mds%d op %s split %llx tracelen %d\n", mds,
+	      ceph_snap_op_name(op), split, trace_len);
 
 	down_write(&mdsc->snap_rwsem);
 	locked_rwsem = 1;
@@ -832,9 +1079,8 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 			if (IS_ERR(realm))
 				goto out;
 		}
-		ceph_get_snap_realm(mdsc, realm);
 
-		dout("splitting snap_realm %llx %p\n", realm->ino, realm);
+		doutc(cl, "splitting snap_realm %llx %p\n", realm->ino, realm);
 		for (i = 0; i < num_split_inos; i++) {
 			struct ceph_vino vino = {
 				.ino = le64_to_cpu(split_inos[i]),
@@ -842,7 +1088,6 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 			};
 			struct inode *inode = ceph_find_inode(sb, vino);
 			struct ceph_inode_info *ci;
-			struct ceph_snap_realm *oldrealm;
 
 			if (!inode)
 				continue;
@@ -860,28 +1105,17 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
 			 */
 			if (ci->i_snap_realm->created >
 			    le64_to_cpu(ri->created)) {
-				dout(" leaving %p in newer realm %llx %p\n",
-				     inode, ci->i_snap_realm->ino,
-				     ci->i_snap_realm);
+				doutc(cl, " leaving %p %llx.%llx in newer realm %llx %p\n",
+				      inode, ceph_vinop(inode), ci->i_snap_realm->ino,
+				      ci->i_snap_realm);
 				goto skip_inode;
 			}
-			dout(" will move %p to split realm %llx %p\n",
-			     inode, realm->ino, realm);
-			/*
-			 * Move the inode to the new realm
-			 */
-			spin_lock(&realm->inodes_with_caps_lock);
-			list_del_init(&ci->i_snap_realm_item);
-			list_add(&ci->i_snap_realm_item,
-				 &realm->inodes_with_caps);
-			oldrealm = ci->i_snap_realm;
-			ci->i_snap_realm = realm;
-			spin_unlock(&realm->inodes_with_caps_lock);
-			spin_unlock(&ci->i_ceph_lock);
+			doutc(cl, " will move %p %llx.%llx to split realm %llx %p\n",
+			      inode, ceph_vinop(inode), realm->ino, realm);
 
 			ceph_get_snap_realm(mdsc, realm);
-			ceph_put_snap_realm(mdsc, oldrealm);
-
+			ceph_change_snap_realm(inode, realm);
+			spin_unlock(&ci->i_ceph_lock);
 			iput(inode);
 			continue;
 
@@ -893,20 +1127,37 @@ skip_inode:
 		/* we may have taken some of the old realm's children. */
 		for (i = 0; i < num_split_realms; i++) {
 			struct ceph_snap_realm *child =
-				ceph_lookup_snap_realm(mdsc,
+				__lookup_snap_realm(mdsc,
 					   le64_to_cpu(split_realms[i]));
 			if (!child)
 				continue;
 			adjust_snap_realm_parent(mdsc, child, realm->ino);
 		}
+	} else {
+		/*
+		 * In the non-split case both 'num_split_inos' and
+		 * 'num_split_realms' should be 0, making this a no-op.
+		 * However the MDS happens to populate 'split_realms' list
+		 * in one of the UPDATE op cases by mistake.
+		 *
+		 * Skip both lists just in case to ensure that 'p' is
+		 * positioned at the start of realm info, as expected by
+		 * ceph_update_snap_trace().
+		 */
+		p += sizeof(u64) * num_split_inos;
+		p += sizeof(u64) * num_split_realms;
 	}
 
 	/*
 	 * update using the provided snap trace. if we are deleting a
 	 * snap, we can avoid queueing cap_snaps.
 	 */
-	ceph_update_snap_trace(mdsc, p, e,
-			       op == CEPH_SNAP_OP_DESTROY);
+	if (ceph_update_snap_trace(mdsc, p, e,
+				   op == CEPH_SNAP_OP_DESTROY,
+				   NULL)) {
+		close_sessions = true;
+		goto bad;
+	}
 
 	if (op == CEPH_SNAP_OP_SPLIT)
 		/* we took a reference when we created the realm, above */
@@ -917,16 +1168,176 @@ skip_inode:
 	up_write(&mdsc->snap_rwsem);
 
 	flush_snaps(mdsc);
+	ceph_dec_mds_stopping_blocker(mdsc);
 	return;
 
 bad:
-	pr_err("corrupt snap message from mds%d\n", mds);
+	pr_err_client(cl, "corrupt snap message from mds%d\n", mds);
 	ceph_msg_dump(msg);
 out:
 	if (locked_rwsem)
 		up_write(&mdsc->snap_rwsem);
+
+	ceph_dec_mds_stopping_blocker(mdsc);
+
+	if (close_sessions)
+		ceph_mdsc_close_sessions(mdsc);
 	return;
 }
 
+struct ceph_snapid_map* ceph_get_snapid_map(struct ceph_mds_client *mdsc,
+					    u64 snap)
+{
+	struct ceph_client *cl = mdsc->fsc->client;
+	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) {
+		doutc(cl, "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);
+		doutc(cl, "found snapid map %llx -> %x\n", exist->snap,
+		      exist->dev);
+		return exist;
+	}
+
+	doutc(cl, "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_client *cl = mdsc->fsc->client;
+	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);
+		doutc(cl, "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_client *cl = mdsc->fsc->client;
+	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_client(cl, "snapid map %llx -> %x still in use\n",
+				      sm->snap, sm->dev);
+		}
+		kfree(sm);
+	}
+}