Commit 18f62b86 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: cleanup the COW fallback logic in run_delalloc_nocow 



Use the block group pointer used to track the outstanding NOCOW writes as
a boolean to remove the duplicate nocow variable, and keep it contained
in the main loop to simplify the logic.

Reviewed-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 953fa5ce

fs/btrfs/inode.c

+22 −25
Original line number Diff line number Diff line
@@ -1974,8 +1974,6 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
	int ret;

	bool check_prev = true;

	u64 ino = btrfs_ino(inode);

	struct btrfs_block_group *bg;

	bool nocow = false;

	struct can_nocow_file_extent_args nocow_args = { 0 };



	path = btrfs_alloc_path();
@@ -1993,6 +1991,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
	nocow_args.writeback_path = true;



	while (1) {

		struct btrfs_block_group *nocow_bg = NULL;

		struct btrfs_ordered_extent *ordered;

		struct btrfs_key found_key;

		struct btrfs_file_extent_item *fi;
@@ -2003,8 +2002,6 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
		int extent_type;

		bool is_prealloc;



		nocow = false;



		ret = btrfs_lookup_file_extent(NULL, root, path, ino,

					       cur_offset, 0);

		if (ret < 0)
@@ -2063,7 +2060,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
		if (found_key.offset > cur_offset) {

			extent_end = found_key.offset;

			extent_type = 0;

			goto out_check;

			goto must_cow;

		}



		/*
@@ -2096,18 +2093,19 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
		if (ret < 0)

			goto error;

		if (ret == 0)

			goto out_check;

			goto must_cow;



		ret = 0;

		bg = btrfs_inc_nocow_writers(fs_info, nocow_args.disk_bytenr);

		if (bg)

			nocow = true;

out_check:

		nocow_bg = btrfs_inc_nocow_writers(fs_info, nocow_args.disk_bytenr);

		if (!nocow_bg) {

must_cow:

			/*

		 * If nocow is false then record the beginning of the range

		 * that needs to be COWed

			 * If we can't perform NOCOW writeback for the range,

			 * then record the beginning of the range that needs to

			 * be COWed.  It will be written out before the next

			 * NOCOW range if we find one, or when exiting this

			 * loop.

			 */

		if (!nocow) {

			if (cow_start == (u64)-1)

				cow_start = cur_offset;

			cur_offset = extent_end;
@@ -2128,9 +2126,11 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
			ret = fallback_to_cow(inode, locked_page,

					      cow_start, found_key.offset - 1);

			cow_start = (u64)-1;

			if (ret)

			if (ret) {

				btrfs_dec_nocow_writers(nocow_bg);

				goto error;

			}

		}



		nocow_end = cur_offset + nocow_args.num_bytes - 1;

		is_prealloc = extent_type == BTRFS_FILE_EXTENT_PREALLOC;
@@ -2146,6 +2146,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
					  ram_bytes, BTRFS_COMPRESS_NONE,

					  BTRFS_ORDERED_PREALLOC);

			if (IS_ERR(em)) {

				btrfs_dec_nocow_writers(nocow_bg);

				ret = PTR_ERR(em);

				goto error;

			}
@@ -2159,6 +2160,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
				? (1 << BTRFS_ORDERED_PREALLOC)

				: (1 << BTRFS_ORDERED_NOCOW),

				BTRFS_COMPRESS_NONE);

		btrfs_dec_nocow_writers(nocow_bg);

		if (IS_ERR(ordered)) {

			if (is_prealloc) {

				btrfs_drop_extent_map_range(inode, cur_offset,
@@ -2168,11 +2170,6 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
			goto error;

		}



		if (nocow) {

			btrfs_dec_nocow_writers(bg);

			nocow = false;

		}



		if (btrfs_is_data_reloc_root(root))

			/*

			 * Error handled later, as we must prevent
@@ -2213,10 +2210,10 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
			goto error;

	}



error:

	if (nocow)

		btrfs_dec_nocow_writers(bg);

	btrfs_free_path(path);

	return 0;



error:

	/*

	 * If an error happened while a COW region is outstanding, cur_offset

	 * needs to be reset to cow_start to ensure the COW region is unlocked
@@ -2224,7 +2221,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, 
	 */

	if (cow_start != (u64)-1)

		cur_offset = cow_start;

	if (ret && cur_offset < end)

	if (cur_offset < end)

		extent_clear_unlock_delalloc(inode, cur_offset, end,

					     locked_page, EXTENT_LOCKED |

					     EXTENT_DELALLOC | EXTENT_DEFRAG |