Commit 16d299ac authored by Josef Bacik's avatar Josef Bacik
Browse files

Btrfs: reuse the extent_map we found when calling btrfs_get_extent 



In btrfs_get_block_direct we call btrfs_get_extent to lookup the extent for the
range that we are looking for.  If we don't find an extent, btrfs_get_extent
will insert a extent_map for that area and mark it as a hole.  So it does the
job of allocating a new extent map and inserting it into the io tree.  But if
we're creating a new extent we free it up and redo all of that work.  So instead
pass the em to btrfs_new_extent_direct(), and if it will work just allocate the
disk space and set it up properly and bypass the freeing/allocating of a new
extent map and the expensive operation of inserting the thing into the io_tree.
Thanks,

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
parent 1ae39938

fs/btrfs/inode.c

+28 −8
Original line number Diff line number Diff line
@@ -5445,17 +5445,30 @@ out: 
}



static struct extent_map *btrfs_new_extent_direct(struct inode *inode,

						  struct extent_map *em,

						  u64 start, u64 len)

{

	struct btrfs_root *root = BTRFS_I(inode)->root;

	struct btrfs_trans_handle *trans;

	struct extent_map *em;

	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;

	struct btrfs_key ins;

	u64 alloc_hint;

	int ret;

	bool insert = false;



	/*

	 * Ok if the extent map we looked up is a hole and is for the exact

	 * range we want, there is no reason to allocate a new one, however if

	 * it is not right then we need to free this one and drop the cache for

	 * our range.

	 */

	if (em->block_start != EXTENT_MAP_HOLE || em->start != start ||

	    em->len != len) {

		free_extent_map(em);

		em = NULL;

		insert = true;

		btrfs_drop_extent_cache(inode, start, start + len - 1, 0);

	}



	trans = btrfs_join_transaction(root, 0);

	if (IS_ERR(trans))
@@ -5471,11 +5484,13 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode, 
		goto out;

	}



	if (!em) {

		em = alloc_extent_map(GFP_NOFS);

		if (!em) {

			em = ERR_PTR(-ENOMEM);

			goto out;

		}

	}



	em->start = start;

	em->orig_start = em->start;
@@ -5484,9 +5499,15 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode, 
	em->block_start = ins.objectid;

	em->block_len = ins.offset;

	em->bdev = root->fs_info->fs_devices->latest_bdev;



	/*

	 * We need to do this because if we're using the original em we searched

	 * for, we could have EXTENT_FLAG_VACANCY set, and we don't want that.

	 */

	em->flags = 0;

	set_bit(EXTENT_FLAG_PINNED, &em->flags);



	while (1) {

	while (insert) {

		write_lock(&em_tree->lock);

		ret = add_extent_mapping(em_tree, em);

		write_unlock(&em_tree->lock);
@@ -5704,8 +5725,7 @@ must_cow: 
	 * it above

	 */

	len = bh_result->b_size;

	free_extent_map(em);

	em = btrfs_new_extent_direct(inode, start, len);

	em = btrfs_new_extent_direct(inode, em, start, len);

	if (IS_ERR(em))

		return PTR_ERR(em);

	len = min(len, em->len - (start - em->start));

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