Btrfs: Add mount -o nodatasum to turn of file data checksumming

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

fs/btrfs/ctree.h

@@ -321,6 +321,7 @@ struct btrfs_fs_info {
 
 	u64 generation;
 	u64 last_trans_committed;
+	unsigned long mount_opt;
 	struct btrfs_transaction *running_transaction;
 	struct btrfs_super_block super_copy;
 	struct extent_buffer *sb_buffer;
@@ -429,6 +430,13 @@ struct btrfs_root {
  */
 #define BTRFS_STRING_ITEM_KEY	253
 
+#define BTRFS_MOUNT_NODATASUM		0x1
+
+#define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
+#define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)
+#define btrfs_test_opt(root, opt)	((root)->fs_info->mount_opt & \
+					 BTRFS_MOUNT_##opt)
+
 /* some macros to generate set/get funcs for the struct fields.  This
  * assumes there is a lefoo_to_cpu for every type, so lets make a simple
  * one for u8:
@@ -906,12 +914,6 @@ static inline u32 btrfs_level_size(struct btrfs_root *root, int level) {
 	((unsigned long)(btrfs_leaf_data(leaf) + \
 	btrfs_item_offset_nr(leaf, slot)))
 
-/* mount option defines and helpers */
-#define BTRFS_MOUNT_SUBVOL		0x000001
-#define btrfs_clear_opt(o, opt)		o &= ~BTRFS_MOUNT_##opt
-#define btrfs_set_opt(o, opt)		o |= BTRFS_MOUNT_##opt
-#define btrfs_test_opt(sb, opt)		(BTRFS_SB(sb)->s_mount_opt & \
-					 BTRFS_MOUNT_##opt)
 /* extent-tree.c */
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
 			 struct btrfs_root *root);

fs/btrfs/disk-io.c

@@ -568,6 +568,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	fs_info->tree_root = tree_root;
 	fs_info->extent_root = extent_root;
 	fs_info->sb = sb;
+	fs_info->mount_opt = 0;
 	fs_info->btree_inode = new_inode(sb);
 	fs_info->btree_inode->i_ino = 1;
 	fs_info->btree_inode->i_nlink = 1;

fs/btrfs/inode.c

@@ -116,10 +116,13 @@ int btrfs_writepage_io_hook(struct page *page, u64 start, u64 end)
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
 	char *kaddr;
-	int ret;
+	int ret = 0;
 	u64 page_start = (u64)page->index << PAGE_CACHE_SHIFT;
 	size_t offset = start - page_start;
 
+	if (btrfs_test_opt(root, NODATASUM))
+		return 0;
+
 	mutex_lock(&root->fs_info->fs_mutex);
 	trans = btrfs_start_transaction(root, 1);
 	btrfs_set_trans_block_group(trans, inode);
@@ -143,6 +146,9 @@ int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
 	struct btrfs_path *path = NULL;
 	u32 csum;
 
+	if (btrfs_test_opt(root, NODATASUM))
+		return 0;
+
 	mutex_lock(&root->fs_info->fs_mutex);
 	path = btrfs_alloc_path();
 	item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, start, 0);
@@ -176,6 +182,9 @@ int btrfs_readpage_end_io_hook(struct page *page, u64 start, u64 end)
 	u32 csum = ~(u32)0;
 	unsigned long flags;
 
+	if (btrfs_test_opt(root, NODATASUM))
+		return 0;
+
 	ret = get_state_private(em_tree, start, &private);
 	local_irq_save(flags);
 	kaddr = kmap_atomic(page, KM_IRQ0);

fs/btrfs/super.c

@@ -61,11 +61,12 @@ static void btrfs_put_super (struct super_block * sb)
 }
 
 enum {
-	Opt_subvol, Opt_err,
+	Opt_subvol, Opt_nodatasum, Opt_err,
 };
 
 static match_table_t tokens = {
 	{Opt_subvol, "subvol=%s"},
+	{Opt_nodatasum, "nodatasum"},
 	{Opt_err, NULL}
 };
 
@@ -74,7 +75,12 @@ static int parse_options (char * options,
 			  char **subvol_name)
 {
 	char * p;
+	struct btrfs_fs_info *info = NULL;
 	substring_t args[MAX_OPT_ARGS];
+
+	if (root)
+		info = root->fs_info;
+
 	if (!options)
 		return 1;
 
@@ -86,7 +92,12 @@ static int parse_options (char * options,
 		token = match_token(p, tokens, args);
 		switch (token) {
 		case Opt_subvol:
-			*subvol_name = match_strdup(&args[0]);
+			if (subvol_name)
+				*subvol_name = match_strdup(&args[0]);
+			break;
+		case Opt_nodatasum:
+			if (root)
+				btrfs_set_opt(info->mount_opt, NODATASUM);
 			break;
 		default:
 			return 0;
@@ -143,6 +154,8 @@ static int btrfs_fill_super(struct super_block * sb, void * data, int silent)
 		goto fail_close;
 	}
 
+	parse_options((char *)data, tree_root, NULL);
+
 	/* this does the super kobj at the same time */
 	err = btrfs_sysfs_add_super(tree_root->fs_info);
 	if (err)