3 files changed, 42 insertions, 40 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d8e539fe5544..4c476281b66b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -191,6 +191,8 @@ static int btrfs_csum_sizes[] = { 4, 0 };
 /* ioprio of readahead is set to idle */
 #define BTRFS_IOPRIO_READA (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0))
 
+#define BTRFS_DIRTY_METADATA_THRESH     (32 * 1024 * 1024)
+
 /*
  * The key defines the order in the tree, and so it also defines (optimal)
  * block layout.
@@ -1448,10 +1450,9 @@ struct btrfs_fs_info {
 
         u64 total_pinned;
 
-        /* protected by the delalloc lock, used to keep from writing
-         * metadata until there is a nice batch
-         */
-        u64 dirty_metadata_bytes;
+        /* used to keep from writing metadata until there is a nice batch */
+        struct percpu_counter dirty_metadata_bytes;
+        s32 dirty_metadata_batch;
         struct list_head dirty_cowonly_roots;
 
         struct btrfs_fs_devices *fs_devices;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 04f98e3ffd90..34ace168eebc 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -946,18 +946,20 @@ static int btree_writepages(struct address_space *mapping,
                             struct writeback_control *wbc)
 {
         struct extent_io_tree *tree;
+        struct btrfs_fs_info *fs_info;
+        int ret;
+
         tree = &BTRFS_I(mapping->host)->io_tree;
         if (wbc->sync_mode == WB_SYNC_NONE) {
-                struct btrfs_root *root = BTRFS_I(mapping->host)->root;
-                u64 num_dirty;
-                unsigned long thresh = 32 * 1024 * 1024;
 
                 if (wbc->for_kupdate)
                         return 0;
 
+                fs_info = BTRFS_I(mapping->host)->root->fs_info;
                 /* this is a bit racy, but that's ok */
-                num_dirty = root->fs_info->dirty_metadata_bytes;
-                if (num_dirty < thresh)
+                ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+                                             BTRFS_DIRTY_METADATA_THRESH);
+                if (ret < 0)
                         return 0;
         }
         return btree_write_cache_pages(mapping, wbc);
@@ -1125,24 +1127,16 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 void clean_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                       struct extent_buffer *buf)
 {
+        struct btrfs_fs_info *fs_info = root->fs_info;
+
         if (btrfs_header_generation(buf) ==
-            root->fs_info->running_transaction->transid) {
+            fs_info->running_transaction->transid) {
                 btrfs_assert_tree_locked(buf);
 
                 if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
-                        spin_lock(&root->fs_info->delalloc_lock);
-                        if (root->fs_info->dirty_metadata_bytes >= buf->len)
-                                root->fs_info->dirty_metadata_bytes -= buf->len;
-                        else {
-                                spin_unlock(&root->fs_info->delalloc_lock);
-                                btrfs_panic(root->fs_info, -EOVERFLOW,
-                                          "Can't clear %lu bytes from "
-                                          " dirty_mdatadata_bytes (%llu)",
-                                          buf->len,
-                                          root->fs_info->dirty_metadata_bytes);
-                        }
-                        spin_unlock(&root->fs_info->delalloc_lock);
-
+                        __percpu_counter_add(&fs_info->dirty_metadata_bytes,
+                                             -buf->len,
+                                             fs_info->dirty_metadata_batch);
                         /* ugh, clear_extent_buffer_dirty needs to lock the page */
                         btrfs_set_lock_blocking(buf);
                         clear_extent_buffer_dirty(buf);
@@ -2008,10 +2002,18 @@ int open_ctree(struct super_block *sb,
                 goto fail_srcu;
         }
 
+        ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0);
+        if (ret) {
+                err = ret;
+                goto fail_bdi;
+        }
+        fs_info->dirty_metadata_batch = PAGE_CACHE_SIZE *
+                                        (1 + ilog2(nr_cpu_ids));
+
         fs_info->btree_inode = new_inode(sb);
         if (!fs_info->btree_inode) {
                 err = -ENOMEM;
-                goto fail_bdi;
+                goto fail_dirty_metadata_bytes;
         }
 
         mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
@@ -2266,6 +2268,7 @@ int open_ctree(struct super_block *sb,
         leafsize = btrfs_super_leafsize(disk_super);
         sectorsize = btrfs_super_sectorsize(disk_super);
         stripesize = btrfs_super_stripesize(disk_super);
+        fs_info->dirty_metadata_batch = leafsize * (1 + ilog2(nr_cpu_ids));
 
         /*
          * mixed block groups end up with duplicate but slightly offset
@@ -2728,6 +2731,8 @@ fail_iput:
 
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
         iput(fs_info->btree_inode);
+fail_dirty_metadata_bytes:
+        percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
 fail_bdi:
         bdi_destroy(&fs_info->bdi);
 fail_srcu:
@@ -3406,6 +3411,7 @@ int close_ctree(struct btrfs_root *root)
         btrfs_close_devices(fs_info->fs_devices);
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
+        percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
         bdi_destroy(&fs_info->bdi);
         cleanup_srcu_struct(&fs_info->subvol_srcu);
 
@@ -3448,11 +3454,10 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
                         (unsigned long long)transid,
                         (unsigned long long)root->fs_info->generation);
         was_dirty = set_extent_buffer_dirty(buf);
-        if (!was_dirty) {
-                spin_lock(&root->fs_info->delalloc_lock);
-                root->fs_info->dirty_metadata_bytes += buf->len;
-                spin_unlock(&root->fs_info->delalloc_lock);
-        }
+        if (!was_dirty)
+                __percpu_counter_add(&root->fs_info->dirty_metadata_bytes,
+                                     buf->len,
+                                     root->fs_info->dirty_metadata_batch);
 }
 
 static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
@@ -3462,8 +3467,7 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
          * looks as though older kernels can get into trouble with
          * this code, they end up stuck in balance_dirty_pages forever
          */
-        u64 num_dirty;
-        unsigned long thresh = 32 * 1024 * 1024;
+        int ret;
 
         if (current->flags & PF_MEMALLOC)
                 return;
@@ -3471,9 +3475,9 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
         if (flush_delayed)
                 btrfs_balance_delayed_items(root);
 
-        num_dirty = root->fs_info->dirty_metadata_bytes;
-
-        if (num_dirty > thresh) {
+        ret = percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
+                                     BTRFS_DIRTY_METADATA_THRESH);
+        if (ret > 0) {
                 balance_dirty_pages_ratelimited_nr(
                                    root->fs_info->btree_inode->i_mapping, 1);
         }
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index bda36fef301e..b9019c847c58 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3122,12 +3122,9 @@ static int lock_extent_buffer_for_io(struct extent_buffer *eb,
                 set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
                 spin_unlock(&eb->refs_lock);
                 btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
-                spin_lock(&fs_info->delalloc_lock);
-                if (fs_info->dirty_metadata_bytes >= eb->len)
-                        fs_info->dirty_metadata_bytes -= eb->len;
-                else
-                        WARN_ON(1);
-                spin_unlock(&fs_info->delalloc_lock);
+                __percpu_counter_add(&fs_info->dirty_metadata_bytes,
+                                     -eb->len,
+                                     fs_info->dirty_metadata_batch);
                 ret = 1;
         } else {
                 spin_unlock(&eb->refs_lock);