On 22.12.2017 00:42, Liu Bo wrote:
> This is a prepare work for the following extent map selftest, which
> runs tests against em merge logic.
>
> Signed-off-by: Liu Bo <bo.li....@oracle.com>
> ---
> fs/btrfs/ctree.h | 2 ++
> fs/btrfs/inode.c | 101
> ++++++++++++++++++++++++++++++-------------------------
> 2 files changed, 58 insertions(+), 45 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index b2e09fe..328f40f 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -3148,6 +3148,8 @@ struct btrfs_delalloc_work
> *btrfs_alloc_delalloc_work(struct inode *inode,
> int delay_iput);
> void btrfs_wait_and_free_delalloc_work(struct btrfs_delalloc_work *work);
>
> +int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
> + struct extent_map **em_in, u64 start, u64 len);
> struct extent_map *btrfs_get_extent_fiemap(struct btrfs_inode *inode,
> struct page *page, size_t pg_offset, u64 start,
> u64 len, int create);
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index e1a7f3c..527df6f 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -6911,6 +6911,61 @@ static noinline int uncompress_inline(struct
> btrfs_path *path,
> return ret;
> }
>
> +int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
> + struct extent_map **em_in, u64 start, u64 len)
How about adding the following comment above the function:
/**
* btrfs_add_extent_mapping - try to add given extent mapping
* @em_tree - the extent tree into which we want to add the mapping
* @em_in - extent we are inserting
* @start - the start of the logical range of the extent we are adding
* @len - logical length of the extent
*
* Insert @em_in into @em_tree. In case there is an overlapping range, handle
* the -EEXIST by either:
* a) Returning the existing extent in @em_in if there is a full overlap
* b) Merge the extents if they are near each other.
*
* Returns 0 on success or a negative error code
*
*/
Also one thing which I'm not very clear is why do we need the start/len, aren't
those already set in em_in ?
> +{
> + int ret;
> + struct extent_map *em = *em_in;
> +
> + ret = add_extent_mapping(em_tree, em, 0);
> + /* it is possible that someone inserted the extent into the tree
> + * while we had the lock dropped. It is also possible that
> + * an overlapping map exists in the tree
> + */
> + if (ret == -EEXIST) {
> + struct extent_map *existing;
> +
> + ret = 0;
> +
> + existing = search_extent_mapping(em_tree, start, len);
> +
> + /*
> + * existing will always be non-NULL, since there must be
> + * extent causing the -EEXIST.
> + */
> + if (existing->start == em->start &&
> + extent_map_end(existing) >= extent_map_end(em) &&
> + em->block_start == existing->block_start) {
> + /*
> + * The existing extent map already encompasses the
> + * entire extent map we tried to add.
> + */
> + free_extent_map(em);
> + *em_in = existing;
> + ret = 0;
> + } else if (start >= extent_map_end(existing) ||
> + start <= existing->start) {
> + /*
> + * The existing extent map is the one nearest to
> + * the [start, start + len) range which overlaps
> + */
> + ret = merge_extent_mapping(em_tree, existing,
> + em, start);
> + free_extent_map(existing);
> + if (ret) {
> + free_extent_map(em);
> + *em_in = NULL;
> + }
> + } else {
> + free_extent_map(em);
> + *em_in = existing;
> + ret = 0;
> + }
> + }
> + ASSERT(ret == 0 || ret == -EEXIST);
> + return ret;
> +}
> +
> /*
> * a bit scary, this does extent mapping from logical file offset to the
> disk.
> * the ugly parts come from merging extents from the disk with the in-ram
> @@ -7147,51 +7202,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode
> *inode,
>
> err = 0;
> write_lock(&em_tree->lock);
> - ret = add_extent_mapping(em_tree, em, 0);
> - /* it is possible that someone inserted the extent into the tree
> - * while we had the lock dropped. It is also possible that
> - * an overlapping map exists in the tree
> - */
> - if (ret == -EEXIST) {
> - struct extent_map *existing;
> -
> - ret = 0;
> -
> - existing = search_extent_mapping(em_tree, start, len);
> - /*
> - * existing will always be non-NULL, since there must be
> - * extent causing the -EEXIST.
> - */
> - if (existing->start == em->start &&
> - extent_map_end(existing) >= extent_map_end(em) &&
> - em->block_start == existing->block_start) {
> - /*
> - * The existing extent map already encompasses the
> - * entire extent map we tried to add.
> - */
> - free_extent_map(em);
> - em = existing;
> - err = 0;
> -
> - } else if (start >= extent_map_end(existing) ||
> - start <= existing->start) {
> - /*
> - * The existing extent map is the one nearest to
> - * the [start, start + len) range which overlaps
> - */
> - err = merge_extent_mapping(em_tree, existing,
> - em, start);
> - free_extent_map(existing);
> - if (err) {
> - free_extent_map(em);
> - em = NULL;
> - }
> - } else {
> - free_extent_map(em);
> - em = existing;
> - err = 0;
> - }
> - }
> + err = btrfs_add_extent_mapping(em_tree, &em, start, len);
> write_unlock(&em_tree->lock);
> out:
>
>
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