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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: Josef Bacik <josef@redhat.com>
This commit is contained in:
Josef Bacik 2011-04-06 14:53:07 -04:00
parent 1ae3993825
commit 16d299ac74
1 changed files with 28 additions and 8 deletions
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36
fs/btrfs/inode.c
View File

@ -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;
btrfs_drop_extent_cache(inode, start, start + len - 1, 0);
/*
* 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))
@ -5471,10 +5484,12 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
goto out;
}
em = alloc_extent_map(GFP_NOFS);
if (!em) {
em = ERR_PTR(-ENOMEM);
goto out;
em = alloc_extent_map(GFP_NOFS);
if (!em) {
em = ERR_PTR(-ENOMEM);
goto out;
}
}
em->start = 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));