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Commit 94fcca9f authored by Yan, Zheng's avatar Yan, Zheng Committed by Chris Mason
Browse files

Btrfs: optimize back reference update during btrfs_drop_snapshot 



This patch reading level 0 tree blocks that already use full backrefs.

Signed-off-by: default avatarYan Zheng <zheng.yan@oracle.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent efefb143

fs/btrfs/extent-tree.c

+53 −29
Original line number Diff line number Diff line
@@ -4911,6 +4911,7 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans, 
	u64 bytenr;

	u64 generation;

	u64 refs;

	u64 flags;

	u64 last = 0;

	u32 nritems;

	u32 blocksize;
@@ -4948,15 +4949,19 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans, 
		    generation <= root->root_key.offset)

			continue;



		if (wc->stage == DROP_REFERENCE) {

			ret = btrfs_lookup_extent_info(trans, root,

						bytenr, blocksize,

						&refs, NULL);

		/* We don't lock the tree block, it's OK to be racy here */

		ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,

					       &refs, &flags);

		BUG_ON(ret);

		BUG_ON(refs == 0);



		if (wc->stage == DROP_REFERENCE) {

			if (refs == 1)

				goto reada;



			if (wc->level == 1 &&

			    (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))

				continue;

			if (!wc->update_ref ||

			    generation <= root->root_key.offset)

				continue;
@@ -4965,6 +4970,10 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans, 
						  &wc->update_progress);

			if (ret < 0)

				continue;

		} else {

			if (wc->level == 1 &&

			    (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))

				continue;

		}

reada:

		ret = readahead_tree_block(root, bytenr, blocksize,
@@ -4988,7 +4997,7 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans, 
static noinline int walk_down_proc(struct btrfs_trans_handle *trans,

				   struct btrfs_root *root,

				   struct btrfs_path *path,

				   struct walk_control *wc)

				   struct walk_control *wc, int lookup_info)

{

	int level = wc->level;

	struct extent_buffer *eb = path->nodes[level];
@@ -5003,8 +5012,9 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans, 
	 * when reference count of tree block is 1, it won't increase

	 * again. once full backref flag is set, we never clear it.

	 */

	if ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||

	    (wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag))) {

	if (lookup_info &&

	    ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||

	     (wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag)))) {

		BUG_ON(!path->locks[level]);

		ret = btrfs_lookup_extent_info(trans, root,

					       eb->start, eb->len,
@@ -5065,7 +5075,7 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans, 
static noinline int do_walk_down(struct btrfs_trans_handle *trans,

				 struct btrfs_root *root,

				 struct btrfs_path *path,

				 struct walk_control *wc)

				 struct walk_control *wc, int *lookup_info)

{

	u64 bytenr;

	u64 generation;
@@ -5085,8 +5095,10 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
	 * for the subtree

	 */

	if (wc->stage == UPDATE_BACKREF &&

	    generation <= root->root_key.offset)

	    generation <= root->root_key.offset) {

		*lookup_info = 1;

		return 1;

	}



	bytenr = btrfs_node_blockptr(path->nodes[level], path->slots[level]);

	blocksize = btrfs_level_size(root, level - 1);
@@ -5099,14 +5111,19 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
	btrfs_tree_lock(next);

	btrfs_set_lock_blocking(next);



	if (wc->stage == DROP_REFERENCE) {

	ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,

				       &wc->refs[level - 1],

				       &wc->flags[level - 1]);

	BUG_ON(ret);

	BUG_ON(wc->refs[level - 1] == 0);

	*lookup_info = 0;



	if (wc->stage == DROP_REFERENCE) {

		if (wc->refs[level - 1] > 1) {

			if (level == 1 &&

			    (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))

				goto skip;



			if (!wc->update_ref ||

			    generation <= root->root_key.offset)

				goto skip;
@@ -5120,12 +5137,17 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
			wc->stage = UPDATE_BACKREF;

			wc->shared_level = level - 1;

		}

	} else {

		if (level == 1 &&

		    (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))

			goto skip;

	}



	if (!btrfs_buffer_uptodate(next, generation)) {

		btrfs_tree_unlock(next);

		free_extent_buffer(next);

		next = NULL;

		*lookup_info = 1;

	}



	if (!next) {
@@ -5148,7 +5170,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
skip:

	wc->refs[level - 1] = 0;

	wc->flags[level - 1] = 0;



	if (wc->stage == DROP_REFERENCE) {

		if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) {

			parent = path->nodes[level]->start;

		} else {
@@ -5160,9 +5182,10 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
		ret = btrfs_free_extent(trans, root, bytenr, blocksize, parent,

					root->root_key.objectid, level - 1, 0);

		BUG_ON(ret);



	}

	btrfs_tree_unlock(next);

	free_extent_buffer(next);

	*lookup_info = 1;

	return 1;

}
@@ -5276,6 +5299,7 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans, 
				   struct walk_control *wc)

{

	int level = wc->level;

	int lookup_info = 1;

	int ret;



	while (level >= 0) {
@@ -5283,14 +5307,14 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans, 
		    btrfs_header_nritems(path->nodes[level]))

			break;



		ret = walk_down_proc(trans, root, path, wc);

		ret = walk_down_proc(trans, root, path, wc, lookup_info);

		if (ret > 0)

			break;



		if (level == 0)

			break;



		ret = do_walk_down(trans, root, path, wc);

		ret = do_walk_down(trans, root, path, wc, &lookup_info);

		if (ret > 0) {

			path->slots[level]++;

			continue;