btrfs: add helper for fs_info->closing

wrap checking of filesystem 'closing' flag and fix a few missing memory
barriers.
Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/ctree.h

@@ -2354,6 +2354,15 @@ int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root,
 			struct extent_buffer *node,
 			struct extent_buffer *parent);
+static inline int btrfs_fs_closing(struct btrfs_fs_info *fs_info)
+{
+	/*
+	 * Get synced with close_ctree()
+	 */
+	smp_mb();
+	return fs_info->closing;
+}
+
 /* root-item.c */
 int btrfs_find_root_ref(struct btrfs_root *tree_root,
 			struct btrfs_path *path,

fs/btrfs/extent-tree.c

@@ -366,8 +366,7 @@ static int caching_kthread(void *data)
 	nritems = btrfs_header_nritems(leaf);
 
 	while (1) {
-		smp_mb();
-		if (fs_info->closing > 1) {
+		if (btrfs_fs_closing(fs_info) > 1) {
 			last = (u64)-1;
 			break;
 		}

fs/btrfs/file.c

@@ -129,7 +129,7 @@ int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
 	if (!btrfs_test_opt(root, AUTO_DEFRAG))
 		return 0;
 
-	if (root->fs_info->closing)
+	if (btrfs_fs_closing(root->fs_info))
 		return 0;
 
 	if (BTRFS_I(inode)->in_defrag)
@@ -229,7 +229,7 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
 		first_ino = defrag->ino + 1;
 		rb_erase(&defrag->rb_node, &fs_info->defrag_inodes);
 
-		if (fs_info->closing)
+		if (btrfs_fs_closing(fs_info))
 			goto next_free;
 
 		spin_unlock(&fs_info->defrag_inodes_lock);

fs/btrfs/free-space-cache.c

@@ -98,7 +98,7 @@ struct inode *lookup_free_space_inode(struct btrfs_root *root,
 		return inode;
 
 	spin_lock(&block_group->lock);
-	if (!root->fs_info->closing) {
+	if (!btrfs_fs_closing(root->fs_info)) {
 		block_group->inode = igrab(inode);
 		block_group->iref = 1;
 	}
@@ -493,8 +493,7 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
 	 * If we're unmounting then just return, since this does a search on the
 	 * normal root and not the commit root and we could deadlock.
 	 */
-	smp_mb();
-	if (fs_info->closing)
+	if (btrfs_fs_closing(fs_info))
 		return 0;
 
 	/*
@@ -2513,7 +2512,7 @@ struct inode *lookup_free_ino_inode(struct btrfs_root *root,
 		return inode;
 
 	spin_lock(&root->cache_lock);
-	if (!root->fs_info->closing)
+	if (!btrfs_fs_closing(root->fs_info))
 		root->cache_inode = igrab(inode);
 	spin_unlock(&root->cache_lock);
 
@@ -2543,8 +2542,7 @@ int load_free_ino_cache(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
 	 * If we're unmounting then just return, since this does a search on the
 	 * normal root and not the commit root and we could deadlock.
 	 */
-	smp_mb();
-	if (fs_info->closing)
+	if (btrfs_fs_closing(fs_info))
 		return 0;
 
 	path = btrfs_alloc_path();

fs/btrfs/inode-map.c

@@ -62,8 +62,7 @@ static int caching_kthread(void *data)
 		goto out;
 
 	while (1) {
-		smp_mb();
-		if (fs_info->closing)
+		if (btrfs_fs_closing(fs_info))
 			goto out;
 
 		leaf = path->nodes[0];

fs/btrfs/inode.c

@@ -4266,8 +4266,7 @@ int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	if (BTRFS_I(inode)->dummy_inode)
 		return 0;
 
-	smp_mb();
-	if (root->fs_info->closing && is_free_space_inode(root, inode))
+	if (btrfs_fs_closing(root->fs_info) && is_free_space_inode(root, inode))
 		nolock = true;
 
 	if (wbc->sync_mode == WB_SYNC_ALL) {

fs/btrfs/scrub.c

@@ -1183,7 +1183,7 @@ int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
 	int ret;
 	struct btrfs_device *dev;
 
-	if (root->fs_info->closing)
+	if (btrfs_fs_closing(root->fs_info))
 		return -EINVAL;
 
 	/*

fs/btrfs/transaction.c

@@ -817,7 +817,7 @@ int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 		btrfs_btree_balance_dirty(info->tree_root, nr);
 		cond_resched();
 
-		if (root->fs_info->closing || ret != -EAGAIN)
+		if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)
 			break;
 	}
 	root->defrag_running = 0;