Commit a1ba4c08 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: add helper to replace extent map range with a new extent map 



We have several places that need to drop all the extent maps in a given
file range and then add a new extent map for that range. Currently they
call btrfs_drop_extent_map_range() to delete all extent maps in the range
and then keep trying to add the new extent map in a loop that keeps
retrying while the insertion of the new extent map fails with -EEXIST.

So instead of repeating this logic, add a helper to extent_map.c that
does these steps and name it btrfs_replace_extent_map_range(). Also add
a comment about why the retry loop is necessary.

Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 9c9d1b4f

fs/btrfs/extent_map.c

+41 −0
Original line number Diff line number Diff line
@@ -879,3 +879,44 @@ void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end, 
	free_extent_map(split);

	free_extent_map(split2);

}



/*

 * Replace a range in the inode's extent map tree with a new extent map.

 *

 * @inode:      The target inode.

 * @new_em:     The new extent map to add to the inode's extent map tree.

 * @modified:   Indicate if the new extent map should be added to the list of

 *              modified extents (for fast fsync tracking).

 *

 * Drops all the extent maps in the inode's extent map tree that intersect the

 * range of the new extent map and adds the new extent map to the tree.

 * The caller should have locked an appropriate file range in the inode's io

 * tree before calling this function.

 */

int btrfs_replace_extent_map_range(struct btrfs_inode *inode,

				   struct extent_map *new_em,

				   bool modified)

{

	const u64 end = new_em->start + new_em->len - 1;

	struct extent_map_tree *tree = &inode->extent_tree;

	int ret;



	ASSERT(!extent_map_in_tree(new_em));



	/*

	 * The caller has locked an appropriate file range in the inode's io

	 * tree, but getting -EEXIST when adding the new extent map can still

	 * happen in case there are extents that partially cover the range, and

	 * this is due to two tasks operating on different parts of the extent.

	 * See commit 18e83ac75bfe67 ("Btrfs: fix unexpected EEXIST from

	 * btrfs_get_extent") for an example and details.

	 */

	do {

		btrfs_drop_extent_map_range(inode, new_em->start, end, false);

		write_lock(&tree->lock);

		ret = add_extent_mapping(tree, new_em, modified);

		write_unlock(&tree->lock);

	} while (ret == -EEXIST);



	return ret;

}

fs/btrfs/extent_map.h

+3 −0
Original line number Diff line number Diff line
@@ -109,5 +109,8 @@ int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info, 
void btrfs_drop_extent_map_range(struct btrfs_inode *inode,

				 u64 start, u64 end,

				 bool skip_pinned);

int btrfs_replace_extent_map_range(struct btrfs_inode *inode,

				   struct extent_map *new_em,

				   bool modified);



#endif

fs/btrfs/file.c

+1 −7
Original line number Diff line number Diff line
@@ -2359,7 +2359,6 @@ static int fill_holes(struct btrfs_trans_handle *trans, 
	struct extent_buffer *leaf;

	struct btrfs_file_extent_item *fi;

	struct extent_map *hole_em;

	struct extent_map_tree *em_tree = &inode->extent_tree;

	struct btrfs_key key;

	int ret;
@@ -2440,12 +2439,7 @@ static int fill_holes(struct btrfs_trans_handle *trans, 
		hole_em->compress_type = BTRFS_COMPRESS_NONE;

		hole_em->generation = trans->transid;



		do {

			btrfs_drop_extent_map_range(inode, offset, end - 1, false);

			write_lock(&em_tree->lock);

			ret = add_extent_mapping(em_tree, hole_em, 1);

			write_unlock(&em_tree->lock);

		} while (ret == -EEXIST);

		ret = btrfs_replace_extent_map_range(inode, hole_em, true);

		free_extent_map(hole_em);

		if (ret)

			btrfs_set_inode_full_sync(inode);

fs/btrfs/inode.c

+8 −42
Original line number Diff line number Diff line
@@ -5051,7 +5051,6 @@ int btrfs_cont_expand(struct btrfs_inode *inode, loff_t oldsize, loff_t size) 
	struct extent_io_tree *io_tree = &inode->io_tree;

	struct extent_map *em = NULL;

	struct extent_state *cached_state = NULL;

	struct extent_map_tree *em_tree = &inode->extent_tree;

	u64 hole_start = ALIGN(oldsize, fs_info->sectorsize);

	u64 block_end = ALIGN(size, fs_info->sectorsize);

	u64 last_byte;
@@ -5099,11 +5098,11 @@ int btrfs_cont_expand(struct btrfs_inode *inode, loff_t oldsize, loff_t size) 
			if (err)

				break;



			hole_em = alloc_extent_map();

			if (!hole_em) {

				btrfs_drop_extent_map_range(inode, cur_offset,

						    cur_offset + hole_size - 1,

						    false);

			hole_em = alloc_extent_map();

			if (!hole_em) {

				btrfs_set_inode_full_sync(inode);

				goto next;

			}
@@ -5118,16 +5117,7 @@ int btrfs_cont_expand(struct btrfs_inode *inode, loff_t oldsize, loff_t size) 
			hole_em->compress_type = BTRFS_COMPRESS_NONE;

			hole_em->generation = fs_info->generation;



			while (1) {

				write_lock(&em_tree->lock);

				err = add_extent_mapping(em_tree, hole_em, 1);

				write_unlock(&em_tree->lock);

				if (err != -EEXIST)

					break;

				btrfs_drop_extent_map_range(inode, cur_offset,

						    cur_offset + hole_size - 1,

						    false);

			}

			err = btrfs_replace_extent_map_range(inode, hole_em, true);

			free_extent_map(hole_em);

		} else {

			err = btrfs_inode_set_file_extent_range(inode,
@@ -7353,7 +7343,6 @@ static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start, 
				       u64 ram_bytes, int compress_type,

				       int type)

{

	struct extent_map_tree *em_tree;

	struct extent_map *em;

	int ret;
@@ -7362,7 +7351,6 @@ static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start, 
	       type == BTRFS_ORDERED_NOCOW ||

	       type == BTRFS_ORDERED_REGULAR);



	em_tree = &inode->extent_tree;

	em = alloc_extent_map();

	if (!em)

		return ERR_PTR(-ENOMEM);
@@ -7383,18 +7371,7 @@ static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start, 
		em->compress_type = compress_type;

	}



	do {

		btrfs_drop_extent_map_range(inode, em->start,

					    em->start + em->len - 1, false);

		write_lock(&em_tree->lock);

		ret = add_extent_mapping(em_tree, em, 1);

		write_unlock(&em_tree->lock);

		/*

		 * The caller has taken lock_extent(), who could race with us

		 * to add em?

		 */

	} while (ret == -EEXIST);



	ret = btrfs_replace_extent_map_range(inode, em, true);

	if (ret) {

		free_extent_map(em);

		return ERR_PTR(ret);
@@ -9893,7 +9870,6 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode, 
				       struct btrfs_trans_handle *trans)

{

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

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

	struct extent_map *em;

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

	struct btrfs_key ins;
@@ -9949,11 +9925,10 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode, 
			break;

		}



		btrfs_drop_extent_map_range(BTRFS_I(inode), cur_offset,

					    cur_offset + ins.offset - 1, false);



		em = alloc_extent_map();

		if (!em) {

			btrfs_drop_extent_map_range(BTRFS_I(inode), cur_offset,

					    cur_offset + ins.offset - 1, false);

			btrfs_set_inode_full_sync(BTRFS_I(inode));

			goto next;

		}
@@ -9968,16 +9943,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode, 
		set_bit(EXTENT_FLAG_PREALLOC, &em->flags);

		em->generation = trans->transid;



		while (1) {

			write_lock(&em_tree->lock);

			ret = add_extent_mapping(em_tree, em, 1);

			write_unlock(&em_tree->lock);

			if (ret != -EEXIST)

				break;

			btrfs_drop_extent_map_range(BTRFS_I(inode), cur_offset,

						    cur_offset + ins.offset - 1,

						    false);

		}

		ret = btrfs_replace_extent_map_range(BTRFS_I(inode), em, true);

		free_extent_map(em);

next:

		num_bytes -= ins.offset;

fs/btrfs/relocation.c

+3 −11
Original line number Diff line number Diff line
@@ -2890,7 +2890,6 @@ static noinline_for_stack int prealloc_file_extent_cluster( 
static noinline_for_stack int setup_relocation_extent_mapping(struct inode *inode,

				u64 start, u64 end, u64 block_start)

{

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

	struct extent_map *em;

	int ret = 0;
@@ -2905,17 +2904,10 @@ static noinline_for_stack int setup_relocation_extent_mapping(struct inode *inod 
	set_bit(EXTENT_FLAG_PINNED, &em->flags);



	lock_extent(&BTRFS_I(inode)->io_tree, start, end, NULL);

	while (1) {

		write_lock(&em_tree->lock);

		ret = add_extent_mapping(em_tree, em, 0);

		write_unlock(&em_tree->lock);

		if (ret != -EEXIST) {

			free_extent_map(em);

			break;

		}

		btrfs_drop_extent_map_range(BTRFS_I(inode), start, end, false);

	}

	ret = btrfs_replace_extent_map_range(BTRFS_I(inode), em, false);

	unlock_extent(&BTRFS_I(inode)->io_tree, start, end, NULL);

	free_extent_map(em);



	return ret;

}