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Commit bdf7c00e authored by Josef Bacik's avatar Josef Bacik
Browse files

Btrfs: optimize read_block_for_search 



This patch does two things, first it only does one call to
btrfs_buffer_uptodate() with the gen specified instead of once with 0 and then
again with gen specified.  The other thing is to call btrfs_read_buffer() on the
buffer we've found instead of dropping it and then calling read_tree_block().
This will keep us from doing yet another radix tree lookup for a buffer we've
already found.  Thanks,

Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent fdf8e2ea

fs/btrfs/ctree.c

+20 −27
Original line number Diff line number Diff line
@@ -2359,28 +2359,22 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
	tmp = btrfs_find_tree_block(root, blocknr, blocksize);

	if (tmp) {

		/* first we do an atomic uptodate check */

		if (btrfs_buffer_uptodate(tmp, 0, 1) > 0) {

		if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {

				/*

				 * we found an up to date block without

				 * sleeping, return

				 * right away

				 */

			*eb_ret = tmp;

			return 0;

		}



		/* the pages were up to date, but we failed

		 * the generation number check.  Do a full

		 * read for the generation number that is correct.

		 * We must do this without dropping locks so

		 * we can trust our generation number

		 */

			free_extent_buffer(tmp);

		btrfs_set_path_blocking(p);



		/* now we're allowed to do a blocking uptodate check */

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

			if (tmp && btrfs_buffer_uptodate(tmp, gen, 0) > 0) {

		ret = btrfs_read_buffer(tmp, gen);

		if (!ret) {

			*eb_ret = tmp;

			return 0;

		}
@@ -2388,7 +2382,6 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
		btrfs_release_path(p);

		return -EIO;

	}

	}



	/*

	 * reduce lock contention at high levels