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Commit c8c42864 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: break up btrfs_search_slot into smaller pieces 



btrfs_search_slot was doing too many things at once.  This breaks
it up into more reasonable units.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 04018de5

fs/btrfs/ctree.c

+131 −90
Original line number Diff line number Diff line
@@ -1244,7 +1244,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans, 
 * readahead one full node of leaves, finding things that are close

 * to the block in 'slot', and triggering ra on them.

 */

static noinline void reada_for_search(struct btrfs_root *root,

static void reada_for_search(struct btrfs_root *root,

			     struct btrfs_path *path,

			     int level, int slot, u64 objectid)

{
@@ -1446,6 +1446,117 @@ noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level) 
	}

}



/*

 * helper function for btrfs_search_slot.  The goal is to find a block

 * in cache without setting the path to blocking.  If we find the block

 * we return zero and the path is unchanged.

 *

 * If we can't find the block, we set the path blocking and do some

 * reada.  -EAGAIN is returned and the search must be repeated.

 */

static int

read_block_for_search(struct btrfs_trans_handle *trans,

		       struct btrfs_root *root, struct btrfs_path *p,

		       struct extent_buffer **eb_ret, int level, int slot,

		       struct btrfs_key *key)

{

	u64 blocknr;

	u64 gen;

	u32 blocksize;

	struct extent_buffer *b = *eb_ret;

	struct extent_buffer *tmp;



	blocknr = btrfs_node_blockptr(b, slot);

	gen = btrfs_node_ptr_generation(b, slot);

	blocksize = btrfs_level_size(root, level - 1);



	tmp = btrfs_find_tree_block(root, blocknr, blocksize);

	if (tmp && btrfs_buffer_uptodate(tmp, gen)) {

		*eb_ret = tmp;

		return 0;

	}



	/*

	 * reduce lock contention at high levels

	 * of the btree by dropping locks before

	 * we read.

	 */

	btrfs_release_path(NULL, p);

	if (tmp)

		free_extent_buffer(tmp);

	if (p->reada)

		reada_for_search(root, p, level, slot, key->objectid);



	tmp = read_tree_block(root, blocknr, blocksize, gen);

	if (tmp)

		free_extent_buffer(tmp);

	return -EAGAIN;

}



/*

 * helper function for btrfs_search_slot.  This does all of the checks

 * for node-level blocks and does any balancing required based on

 * the ins_len.

 *

 * If no extra work was required, zero is returned.  If we had to

 * drop the path, -EAGAIN is returned and btrfs_search_slot must

 * start over

 */

static int

setup_nodes_for_search(struct btrfs_trans_handle *trans,

		       struct btrfs_root *root, struct btrfs_path *p,

		       struct extent_buffer *b, int level, int ins_len)

{

	int ret;

	if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=

	    BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {

		int sret;



		sret = reada_for_balance(root, p, level);

		if (sret)

			goto again;



		btrfs_set_path_blocking(p);

		sret = split_node(trans, root, p, level);

		btrfs_clear_path_blocking(p, NULL);



		BUG_ON(sret > 0);

		if (sret) {

			ret = sret;

			goto done;

		}

		b = p->nodes[level];

	} else if (ins_len < 0 && btrfs_header_nritems(b) <

		   BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {

		int sret;



		sret = reada_for_balance(root, p, level);

		if (sret)

			goto again;



		btrfs_set_path_blocking(p);

		sret = balance_level(trans, root, p, level);

		btrfs_clear_path_blocking(p, NULL);



		if (sret) {

			ret = sret;

			goto done;

		}

		b = p->nodes[level];

		if (!b) {

			btrfs_release_path(NULL, p);

			goto again;

		}

		BUG_ON(btrfs_header_nritems(b) == 1);

	}

	return 0;



again:

	ret = -EAGAIN;

done:

	return ret;

}



/*

 * look for key in the tree.  path is filled in with nodes along the way

 * if key is found, we return zero and you can find the item in the leaf
@@ -1464,16 +1575,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
		      ins_len, int cow)

{

	struct extent_buffer *b;

	struct extent_buffer *tmp;

	int slot;

	int ret;

	int level;

	int should_reada = p->reada;

	int lowest_unlock = 1;

	int blocksize;

	u8 lowest_level = 0;

	u64 blocknr;

	u64 gen;



	lowest_level = p->lowest_level;

	WARN_ON(lowest_level && ins_len > 0);
@@ -1502,7 +1608,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
		if (cow) {

			int wret;



			/* is a cow on this block not required */

			/*

			 * if we don't really need to cow this block

			 * then we don't want to set the path blocking,

			 * so we test it here

			 */

			if (btrfs_header_generation(b) == trans->transid &&

			    btrfs_header_owner(b) == root->root_key.objectid &&

			    !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
@@ -1557,51 +1667,15 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
			if (ret && slot > 0)

				slot -= 1;

			p->slots[level] = slot;

			if ((p->search_for_split || ins_len > 0) &&

			    btrfs_header_nritems(b) >=

			    BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {

				int sret;



				sret = reada_for_balance(root, p, level);

				if (sret)

			ret = setup_nodes_for_search(trans, root, p, b, level,

						     ins_len);

			if (ret == -EAGAIN)

				goto again;



				btrfs_set_path_blocking(p);

				sret = split_node(trans, root, p, level);

				btrfs_clear_path_blocking(p, NULL);



				BUG_ON(sret > 0);

				if (sret) {

					ret = sret;

			else if (ret)

				goto done;

				}

			b = p->nodes[level];

			slot = p->slots[level];

			} else if (ins_len < 0 &&

				   btrfs_header_nritems(b) <

				   BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {

				int sret;



				sret = reada_for_balance(root, p, level);

				if (sret)

					goto again;



				btrfs_set_path_blocking(p);

				sret = balance_level(trans, root, p, level);

				btrfs_clear_path_blocking(p, NULL);



				if (sret) {

					ret = sret;

					goto done;

				}

				b = p->nodes[level];

				if (!b) {

					btrfs_release_path(NULL, p);

					goto again;

				}

				slot = p->slots[level];

				BUG_ON(btrfs_header_nritems(b) == 1);

			}

			unlock_up(p, level, lowest_unlock);



			/* this is only true while dropping a snapshot */
@@ -1610,44 +1684,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
				goto done;

			}



			blocknr = btrfs_node_blockptr(b, slot);

			gen = btrfs_node_ptr_generation(b, slot);

			blocksize = btrfs_level_size(root, level - 1);



			tmp = btrfs_find_tree_block(root, blocknr, blocksize);

			if (tmp && btrfs_buffer_uptodate(tmp, gen)) {

				b = tmp;

			} else {

				/*

				 * reduce lock contention at high levels

				 * of the btree by dropping locks before

				 * we read.

				 */

				if (level > 0) {

					btrfs_release_path(NULL, p);

					if (tmp)

						free_extent_buffer(tmp);

					if (should_reada)

						reada_for_search(root, p,

								 level, slot,

								 key->objectid);



					tmp = read_tree_block(root, blocknr,

							 blocksize, gen);

					if (tmp)

						free_extent_buffer(tmp);

			ret = read_block_for_search(trans, root, p,

						    &b, level, slot, key);

			if (ret == -EAGAIN)

				goto again;

				} else {

					btrfs_set_path_blocking(p);

					if (tmp)

						free_extent_buffer(tmp);

					if (should_reada)

						reada_for_search(root, p,

								 level, slot,

								 key->objectid);

					b = read_node_slot(root, b, slot);

				}

			}



			if (!p->skip_locking) {

				int lret;