Commit 92a7cc42 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE 



The name BTRFS_ROOT_REF_COWS is not very clear about the meaning.

In fact, that bit can only be set to those trees:

- Subvolume roots
- Data reloc root
- Reloc roots for above roots

All other trees won't get this bit set.  So just by the result, it is
obvious that, roots with this bit set can have tree blocks shared with
other trees.  Either shared by snapshots, or by reloc roots (an special
snapshot created by relocation).

This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to
make it easier to understand, and update all comment mentioning
"reference counted" to follow the rename.

Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ae3e715f

fs/btrfs/backref.c

+2 −2
Original line number Diff line number Diff line
@@ -2702,7 +2702,7 @@ static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache, 
	root = btrfs_get_fs_root(fs_info, &root_key, false);

	if (IS_ERR(root))

		return PTR_ERR(root);

	if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))

	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))

		cur->cowonly = 1;



	if (btrfs_root_level(&root->root_item) == cur->level) {
@@ -2789,7 +2789,7 @@ static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache, 
				goto out;

			}

			upper->owner = btrfs_header_owner(eb);

			if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))

			if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))

				upper->cowonly = 1;



			/*

fs/btrfs/backref.h

+1 −1
Original line number Diff line number Diff line
@@ -184,7 +184,7 @@ struct btrfs_backref_node { 
	struct extent_buffer *eb;

	/* Level of the tree block */

	unsigned int level:8;

	/* Is the block in non-reference counted tree */

	/* Is the block in a non-shareable tree */

	unsigned int cowonly:1;

	/* 1 if no child node is in the cache */

	unsigned int lowest:1;

fs/btrfs/block-rsv.c

+1 −1
Original line number Diff line number Diff line
@@ -458,7 +458,7 @@ static struct btrfs_block_rsv *get_block_rsv( 
	struct btrfs_fs_info *fs_info = root->fs_info;

	struct btrfs_block_rsv *block_rsv = NULL;



	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||

	if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||

	    (root == fs_info->csum_root && trans->adding_csums) ||

	    (root == fs_info->uuid_root))

		block_rsv = trans->block_rsv;

fs/btrfs/ctree.c

+13 −13
Original line number Diff line number Diff line
@@ -144,9 +144,10 @@ struct extent_buffer *btrfs_root_node(struct btrfs_root *root) 
	return eb;

}



/* cowonly root (everything not a reference counted cow subvolume), just get

 * put onto a simple dirty list.  transaction.c walks this to make sure they

 * get properly updated on disk.

/*

 * Cowonly root (not-shareable trees, everything not subvolume or reloc roots),

 * just get put onto a simple dirty list.  Transaction walks this list to make

 * sure they get properly updated on disk.

 */

static void add_root_to_dirty_list(struct btrfs_root *root)

{
@@ -185,9 +186,9 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans, 
	int level;

	struct btrfs_disk_key disk_key;



	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&

	WARN_ON(test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&

		trans->transid != fs_info->running_transaction->transid);

	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&

	WARN_ON(test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&

		trans->transid != root->last_trans);



	level = btrfs_header_level(buf);
@@ -826,12 +827,11 @@ int btrfs_block_can_be_shared(struct btrfs_root *root, 
			      struct extent_buffer *buf)

{

	/*

	 * Tree blocks not in reference counted trees and tree roots

	 * are never shared. If a block was allocated after the last

	 * snapshot and the block was not allocated by tree relocation,

	 * we know the block is not shared.

	 * Tree blocks not in shareable trees and tree roots are never shared.

	 * If a block was allocated after the last snapshot and the block was

	 * not allocated by tree relocation, we know the block is not shared.

	 */

	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&

	if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&

	    buf != root->node && buf != root->commit_root &&

	    (btrfs_header_generation(buf) <=

	     btrfs_root_last_snapshot(&root->root_item) ||
@@ -1024,9 +1024,9 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans, 


	btrfs_assert_tree_locked(buf);



	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&

	WARN_ON(test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&

		trans->transid != fs_info->running_transaction->transid);

	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&

	WARN_ON(test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&

		trans->transid != root->last_trans);



	level = btrfs_header_level(buf);
@@ -1065,7 +1065,7 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans, 
		return ret;

	}



	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {

	if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) {

		ret = btrfs_reloc_cow_block(trans, root, buf, cow);

		if (ret) {

			btrfs_abort_transaction(trans, ret);

fs/btrfs/ctree.h

+23 −2
Original line number Diff line number Diff line
@@ -969,7 +969,28 @@ enum { 
	 * is used to tell us when more checks are required

	 */

	BTRFS_ROOT_IN_TRANS_SETUP,

	BTRFS_ROOT_REF_COWS,



	/*

	 * Set if tree blocks of this root can be shared by other roots.

	 * Only subvolume trees and their reloc trees have this bit set.

	 * Conflicts with TRACK_DIRTY bit.

	 *

	 * This affects two things:

	 *

	 * - How balance works

	 *   For shareable roots, we need to use reloc tree and do path

	 *   replacement for balance, and need various pre/post hooks for

	 *   snapshot creation to handle them.

	 *

	 *   While for non-shareable trees, we just simply do a tree search

	 *   with COW.

	 *

	 * - How dirty roots are tracked

	 *   For shareable roots, btrfs_record_root_in_trans() is needed to

	 *   track them, while non-subvolume roots have TRACK_DIRTY bit, they

	 *   don't need to set this manually.

	 */

	BTRFS_ROOT_SHAREABLE,

	BTRFS_ROOT_TRACK_DIRTY,

	BTRFS_ROOT_IN_RADIX,

	BTRFS_ROOT_ORPHAN_ITEM_INSERTED,
@@ -1055,7 +1076,7 @@ struct btrfs_root { 
	struct btrfs_key defrag_progress;

	struct btrfs_key defrag_max;



	/* the dirty list is only used by non-reference counted roots */

	/* The dirty list is only used by non-shareable roots */

	struct list_head dirty_list;



	struct list_head root_list;