Btrfs: implement memory reclaim for leaf reference cache

The memory reclaiming issue happens when snapshot exists. In that
case, some cache entries may not be used during old snapshot dropping,
so they will remain in the cache until umount.

The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
the patch makes all dead roots of a given snapshot linked together in order of
create time. After a old snapshot was completely dropped, we check the dead
root list and remove all cache entries created before the oldest dead root in
the list.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

15 files changed, 86 insertions, 69 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 245eb00435dd..c4792062dd53 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -3275,4 +3275,3 @@ int btrfs_previous_item(struct btrfs_root *root,
         }
         return 1;
 }
-
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 83422088c629..be16cd49ef69 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -666,7 +666,8 @@ struct btrfs_root {
         /* the dirty list is only used by non-reference counted roots */
         struct list_head dirty_list;
 
-        spinlock_t orphan_lock;
+        spinlock_t list_lock;
+        struct list_head dead_list;
         struct list_head orphan_list;
 };
 
diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index eb4dd3d75cf9..125094617fe8 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -340,4 +340,3 @@ int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
         }
         return 0;
 }
-
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ec1ba8ddb35f..e826730d750f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -735,8 +735,9 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
 
         INIT_LIST_HEAD(&root->dirty_list);
         INIT_LIST_HEAD(&root->orphan_list);
+        INIT_LIST_HEAD(&root->dead_list);
         spin_lock_init(&root->node_lock);
-        spin_lock_init(&root->orphan_lock);
+        spin_lock_init(&root->list_lock);
         mutex_init(&root->objectid_mutex);
 
         btrfs_leaf_ref_tree_init(&root->ref_tree_struct);
@@ -1717,7 +1718,7 @@ int close_ctree(struct btrfs_root *root)
                 printk("btrfs: at umount reference cache size %Lu\n",
                         fs_info->total_ref_cache_size);
         }
-        
+
         if (fs_info->extent_root->node)
                 free_extent_buffer(fs_info->extent_root->node);
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index fe1ddbd2bfd6..37ca8df30c30 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -867,8 +867,8 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
                 /*
                  * For (parent_gen > 0 && parent_gen > ref_gen):
                  *
-                 * we reach here through the oldest root, therefore 
-                 * all other reference from same snapshot should have 
+                 * we reach here through the oldest root, therefore
+                 * all other reference from same snapshot should have
                  * a larger generation.
                  */
                 if ((root_objectid != btrfs_ref_root(leaf, ref_item)) ||
@@ -954,7 +954,7 @@ int btrfs_cross_ref_exists(struct btrfs_root *root,
                         if (!eb)
                                 continue;
                         extent_start = eb->start;
-                } else 
+                } else
                         extent_start = bytenr;
 
                 ret = get_reference_status(root, extent_start, ref_generation,
@@ -1048,7 +1048,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 struct btrfs_leaf_ref *ref;
                 struct btrfs_extent_info *info;
 
-                ref = btrfs_alloc_leaf_ref(nr_file_extents);
+                ref = btrfs_alloc_leaf_ref(root, nr_file_extents);
                 if (!ref) {
                         WARN_ON(1);
                         goto out;
@@ -1059,7 +1059,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 ref->generation = btrfs_header_generation(buf);
                 ref->nritems = nr_file_extents;
                 info = ref->extents;
-                
+
                 for (i = 0; nr_file_extents > 0 && i < nritems; i++) {
                         u64 disk_bytenr;
                         btrfs_item_key_to_cpu(buf, &key, i);
@@ -1085,7 +1085,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 BUG_ON(!root->ref_tree);
                 ret = btrfs_add_leaf_ref(root, ref);
                 WARN_ON(ret);
-                btrfs_free_leaf_ref(ref);
+                btrfs_free_leaf_ref(root, ref);
         }
 out:
         return 0;
@@ -2316,7 +2316,7 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 }
 
 static int noinline drop_leaf_ref_no_cache(struct btrfs_trans_handle *trans,
-                                           struct btrfs_root *root,
+                                           struct btrfs_root *root,
                                            struct extent_buffer *leaf)
 {
         u64 leaf_owner;
@@ -2367,7 +2367,7 @@ static int noinline drop_leaf_ref_no_cache(struct btrfs_trans_handle *trans,
 }
 
 static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
-                                         struct btrfs_root *root,
+                                         struct btrfs_root *root,
                                          struct btrfs_leaf_ref *ref)
 {
         int i;
@@ -2521,7 +2521,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                                 ret = drop_leaf_ref(trans, root, ref);
                                 BUG_ON(ret);
                                 btrfs_remove_leaf_ref(root, ref);
-                                btrfs_free_leaf_ref(ref);
+                                btrfs_free_leaf_ref(root, ref);
                                 *level = 0;
                                 break;
                         }
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 964ec1622d66..5368e3b6eb96 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3497,4 +3497,3 @@ out:
         return ret;
 }
 EXPORT_SYMBOL(try_release_extent_buffer);
-
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index afe42d00b5a6..2311061f070e 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -422,4 +422,3 @@ int btrfs_csum_truncate(struct btrfs_trans_handle *trans,
         BUG_ON(ret);
         return ret;
 }
-
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ded5281f8463..412ab4a26382 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1095,4 +1095,3 @@ struct file_operations btrfs_file_operations = {
         .compat_ioctl   = btrfs_ioctl,
 #endif
 };
-
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3aa82cec6bf7..7af8be076ee5 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -835,17 +835,17 @@ int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode)
         struct btrfs_root *root = BTRFS_I(inode)->root;
         int ret = 0;
 
-        spin_lock(&root->orphan_lock);
+        spin_lock(&root->list_lock);
 
         /* already on the orphan list, we're good */
         if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
-                spin_unlock(&root->orphan_lock);
+                spin_unlock(&root->list_lock);
                 return 0;
         }
 
         list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);
 
-        spin_unlock(&root->orphan_lock);
+        spin_unlock(&root->list_lock);
 
         /*
          * insert an orphan item to track this unlinked/truncated file
@@ -864,20 +864,20 @@ int btrfs_orphan_del(struct btrfs_trans_handle *trans, struct inode *inode)
         struct btrfs_root *root = BTRFS_I(inode)->root;
         int ret = 0;
 
-        spin_lock(&root->orphan_lock);
+        spin_lock(&root->list_lock);
 
         if (list_empty(&BTRFS_I(inode)->i_orphan)) {
-                spin_unlock(&root->orphan_lock);
+                spin_unlock(&root->list_lock);
                 return 0;
         }
 
         list_del_init(&BTRFS_I(inode)->i_orphan);
         if (!trans) {
-                spin_unlock(&root->orphan_lock);
+                spin_unlock(&root->list_lock);
                 return 0;
         }
 
-        spin_unlock(&root->orphan_lock);
+        spin_unlock(&root->list_lock);
 
         ret = btrfs_del_orphan_item(trans, root, inode->i_ino);
 
@@ -973,9 +973,9 @@ void btrfs_orphan_cleanup(struct btrfs_root *root)
                  * add this inode to the orphan list so btrfs_orphan_del does
                  * the proper thing when we hit it
                  */
-                spin_lock(&root->orphan_lock);
+                spin_lock(&root->list_lock);
                 list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);
-                spin_unlock(&root->orphan_lock);
+                spin_unlock(&root->list_lock);
 
                 /*
                  * if this is a bad inode, means we actually succeeded in
@@ -3269,13 +3269,13 @@ void btrfs_destroy_inode(struct inode *inode)
             BTRFS_I(inode)->i_default_acl != BTRFS_ACL_NOT_CACHED)
                 posix_acl_release(BTRFS_I(inode)->i_default_acl);
 
-        spin_lock(&BTRFS_I(inode)->root->orphan_lock);
+        spin_lock(&BTRFS_I(inode)->root->list_lock);
         if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                 printk(KERN_ERR "BTRFS: inode %lu: inode still on the orphan"
                        " list\n", inode->i_ino);
                 dump_stack();
         }
-        spin_unlock(&BTRFS_I(inode)->root->orphan_lock);
+        spin_unlock(&BTRFS_I(inode)->root->list_lock);
 
         while(1) {
                 ordered = btrfs_lookup_first_ordered_extent(inode, (u64)-1);
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index d617c29787fa..d43e14c7471a 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -56,4 +56,3 @@ int btrfs_tree_locked(struct extent_buffer *eb)
 {
         return mutex_is_locked(&eb->mutex);
 }
-
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index 14d863720302..f1374d597a17 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -198,4 +198,3 @@ void btrfs_print_tree(struct btrfs_root *root, struct extent_buffer *c)
                 free_extent_buffer(next);
         }
 }
-
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index ec9587784a3d..272b9890c982 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -21,12 +21,18 @@
 #include "ref-cache.h"
 #include "transaction.h"
 
-struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents)
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
+                                            int nr_extents)
 {
         struct btrfs_leaf_ref *ref;
+        size_t size = btrfs_leaf_ref_size(nr_extents);
 
-        ref = kmalloc(btrfs_leaf_ref_size(nr_extents), GFP_NOFS);
+        ref = kmalloc(size, GFP_NOFS);
         if (ref) {
+                spin_lock(&root->fs_info->ref_cache_lock);
+                root->fs_info->total_ref_cache_size += size;
+                spin_unlock(&root->fs_info->ref_cache_lock);
+
                 memset(ref, 0, sizeof(*ref));
                 atomic_set(&ref->usage, 1);
                 INIT_LIST_HEAD(&ref->list);
@@ -34,14 +40,20 @@ struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents)
         return ref;
 }
 
-void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref)
+void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 {
         if (!ref)
                 return;
         WARN_ON(atomic_read(&ref->usage) == 0);
         if (atomic_dec_and_test(&ref->usage)) {
+                size_t size = btrfs_leaf_ref_size(ref->nritems);
+
                 BUG_ON(ref->in_tree);
                 kfree(ref);
+
+                spin_lock(&root->fs_info->ref_cache_lock);
+                root->fs_info->total_ref_cache_size -= size;
+                spin_unlock(&root->fs_info->ref_cache_lock);
         }
 }
 
@@ -64,7 +76,7 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
                 else
                         return parent;
         }
-        
+
         entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
         entry->in_tree = 1;
         rb_link_node(node, parent, p);
@@ -91,9 +103,8 @@ static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
         return NULL;
 }
 
-int btrfs_remove_leaf_refs(struct btrfs_root *root)
+int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen)
 {
-        struct rb_node *rb;
         struct btrfs_leaf_ref *ref = NULL;
         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 
@@ -101,17 +112,18 @@ int btrfs_remove_leaf_refs(struct btrfs_root *root)
                 return 0;
 
         spin_lock(&tree->lock);
-        while(!btrfs_leaf_ref_tree_empty(tree)) {
-                rb = rb_first(&tree->root);
-                ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
+        while(!list_empty(&tree->list)) {
+                ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
+                BUG_ON(!ref->in_tree);
+                if (ref->root_gen > max_root_gen)
+                        break;
+
                 rb_erase(&ref->rb_node, &tree->root);
                 ref->in_tree = 0;
                 list_del_init(&ref->list);
 
                 spin_unlock(&tree->lock);
-
-                btrfs_free_leaf_ref(ref);
-
+                btrfs_free_leaf_ref(root, ref);
                 cond_resched();
                 spin_lock(&tree->lock);
         }
@@ -143,7 +155,6 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 {
         int ret = 0;
         struct rb_node *rb;
-        size_t size = btrfs_leaf_ref_size(ref->nritems);
         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 
         spin_lock(&tree->lock);
@@ -151,9 +162,6 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
         if (rb) {
                 ret = -EEXIST;
         } else {
-                spin_lock(&root->fs_info->ref_cache_lock);
-                root->fs_info->total_ref_cache_size += size;
-                spin_unlock(&root->fs_info->ref_cache_lock);
                 atomic_inc(&ref->usage);
                 list_add_tail(&ref->list, &tree->list);
         }
@@ -163,15 +171,10 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 
 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 {
-        size_t size = btrfs_leaf_ref_size(ref->nritems);
         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 
         BUG_ON(!ref->in_tree);
         spin_lock(&tree->lock);
-        
-        spin_lock(&root->fs_info->ref_cache_lock);
-        root->fs_info->total_ref_cache_size -= size;
-        spin_unlock(&root->fs_info->ref_cache_lock);
 
         rb_erase(&ref->rb_node, &tree->root);
         ref->in_tree = 0;
@@ -179,7 +182,6 @@ int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 
         spin_unlock(&tree->lock);
 
-        btrfs_free_leaf_ref(ref);
+        btrfs_free_leaf_ref(root, ref);
         return 0;
 }
-
diff --git a/fs/btrfs/ref-cache.h b/fs/btrfs/ref-cache.h
index 823c049f72f1..c361b321c0c3 100644
--- a/fs/btrfs/ref-cache.h
+++ b/fs/btrfs/ref-cache.h
@@ -30,6 +30,7 @@ struct btrfs_leaf_ref {
         int in_tree;
         atomic_t usage;
 
+        u64 root_gen;
         u64 bytenr;
         u64 owner;
         u64 generation;
@@ -41,14 +42,13 @@ struct btrfs_leaf_ref {
 
 static inline size_t btrfs_leaf_ref_size(int nr_extents)
 {
-        return sizeof(struct btrfs_leaf_ref) + 
+        return sizeof(struct btrfs_leaf_ref) +
                sizeof(struct btrfs_extent_info) * nr_extents;
 }
 
 static inline void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree)
 {
         tree->root.rb_node = NULL;
-        tree->last = NULL;
         INIT_LIST_HEAD(&tree->list);
         spin_lock_init(&tree->lock);
 }
@@ -59,12 +59,13 @@ static inline int btrfs_leaf_ref_tree_empty(struct btrfs_leaf_ref_tree *tree)
 }
 
 void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree);
-struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents);
-void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref);
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
+                                            int nr_extents);
+void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
                                              u64 bytenr);
 int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
-int btrfs_remove_leaf_refs(struct btrfs_root *root);
+int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen);
 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
 
 #endif
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 216f31571620..52c5524896a3 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -98,20 +98,24 @@ static noinline int record_root_in_trans(struct btrfs_root *root)
                         BUG_ON(!dirty);
                         dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
                         BUG_ON(!dirty->root);
-
                         dirty->latest_root = root;
                         INIT_LIST_HEAD(&dirty->list);
 
                         root->commit_root = btrfs_root_node(root);
-                        root->dirty_root = dirty;
 
                         memcpy(dirty->root, root, sizeof(*root));
-                        dirty->root->ref_tree = &root->ref_tree_struct;
-
                         spin_lock_init(&dirty->root->node_lock);
+                        spin_lock_init(&dirty->root->list_lock);
                         mutex_init(&dirty->root->objectid_mutex);
+                        INIT_LIST_HEAD(&dirty->root->dead_list);
                         dirty->root->node = root->commit_root;
                         dirty->root->commit_root = NULL;
+
+                        spin_lock(&root->list_lock);
+                        list_add(&dirty->root->dead_list, &root->dead_list);
+                        spin_unlock(&root->list_lock);
+
+                        root->dirty_root = dirty;
                 } else {
                         WARN_ON(1);
                 }
@@ -356,8 +360,6 @@ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
                 list_del_init(next);
                 root = list_entry(next, struct btrfs_root, dirty_list);
                 update_cowonly_root(trans, root);
-                if (root->fs_info->closing)
-                        btrfs_remove_leaf_refs(root);
         }
         return 0;
 }
@@ -410,7 +412,11 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 
                                 free_extent_buffer(root->commit_root);
                                 root->commit_root = NULL;
-                                
+
+                                spin_lock(&root->list_lock);
+                                list_del_init(&dirty->root->dead_list);
+                                spin_unlock(&root->list_lock);
+
                                 kfree(dirty->root);
                                 kfree(dirty);
 
@@ -497,6 +503,7 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
         unsigned long nr;
         u64 num_bytes;
         u64 bytes_used;
+        u64 max_useless;
         int ret = 0;
         int err;
 
@@ -554,10 +561,25 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
                 }
                 mutex_unlock(&root->fs_info->drop_mutex);
 
+                spin_lock(&root->list_lock);
+                list_del_init(&dirty->root->dead_list);
+                if (!list_empty(&root->dead_list)) {
+                        struct btrfs_root *oldest;
+                        oldest = list_entry(root->dead_list.prev,
+                                            struct btrfs_root, dead_list);
+                        max_useless = oldest->root_key.offset - 1;
+                } else {
+                        max_useless = root->root_key.offset - 1;
+                }
+                spin_unlock(&root->list_lock);
+
                 nr = trans->blocks_used;
                 ret = btrfs_end_transaction(trans, tree_root);
                 BUG_ON(ret);
 
+                ret = btrfs_remove_leaf_refs(root, max_useless);
+                BUG_ON(ret);
+
                 free_extent_buffer(dirty->root->node);
                 kfree(dirty->root);
                 kfree(dirty);
@@ -785,10 +807,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
         put_transaction(cur_trans);
         put_transaction(cur_trans);
 
+        list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
         if (root->fs_info->closing)
                 list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
-        else
-                list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
 
         mutex_unlock(&root->fs_info->trans_mutex);
         kmem_cache_free(btrfs_trans_handle_cachep, trans);
@@ -814,4 +835,3 @@ again:
         }
         return 0;
 }
-
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5e6ee7a6f738..18db4cbe2794 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2527,4 +2527,3 @@ again:
 error:
         return ret;
 }
-