Commit af821cba authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: factor out space reservation code from btrfs_buffered_write() 



Inside the main loop of btrfs_buffered_write(), we have a complex data
and metadata space reservation code, which tries to reserve space for
a COW write, if failed then fallback to check if we can do a NOCOW
write.

Factor out that part of code into a dedicated helper, reserve_space(),
to make the main loop a little easier to read.

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent afe990fb

fs/btrfs/file.c

+59 −45
Original line number Diff line number Diff line
@@ -1094,6 +1094,61 @@ static void release_space(struct btrfs_inode *inode, struct extent_changeset *da 
	}

}



/*

 * Reserve data and metadata space for this buffered write range.

 *

 * Return >0 for the number of bytes reserved, which is always block aligned.

 * Return <0 for error.

 */

static ssize_t reserve_space(struct btrfs_inode *inode,

			     struct extent_changeset **data_reserved,

			     u64 start, size_t *len, bool nowait,

			     bool *only_release_metadata)

{

	const struct btrfs_fs_info *fs_info = inode->root->fs_info;

	const unsigned int block_offset = (start & (fs_info->sectorsize - 1));

	size_t reserve_bytes;

	int ret;



	ret = btrfs_check_data_free_space(inode, data_reserved, start, *len, nowait);

	if (ret < 0) {

		int can_nocow;



		if (nowait && (ret == -ENOSPC || ret == -EAGAIN))

			return -EAGAIN;



		/*

		 * If we don't have to COW at the offset, reserve metadata only.

		 * write_bytes may get smaller than requested here.

		 */

		can_nocow = btrfs_check_nocow_lock(inode, start, len, nowait);

		if (can_nocow < 0)

			ret = can_nocow;

		if (can_nocow > 0)

			ret = 0;

		if (ret)

			return ret;

		*only_release_metadata = true;

	}



	reserve_bytes = round_up(*len + block_offset, fs_info->sectorsize);

	WARN_ON(reserve_bytes == 0);

	ret = btrfs_delalloc_reserve_metadata(inode, reserve_bytes,

					      reserve_bytes, nowait);

	if (ret) {

		if (!*only_release_metadata)

			btrfs_free_reserved_data_space(inode, *data_reserved,

						       start, *len);

		else

			btrfs_check_nocow_unlock(inode);



		if (nowait && ret == -ENOSPC)

			ret = -EAGAIN;

		return ret;

	}

	return reserve_bytes;

}



ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)

{

	struct file *file = iocb->ki_filp;
@@ -1159,52 +1214,11 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i) 
		sector_offset = pos & (fs_info->sectorsize - 1);



		extent_changeset_release(data_reserved);

		ret = btrfs_check_data_free_space(BTRFS_I(inode),

						  &data_reserved, pos,

						  write_bytes, nowait);

		if (ret < 0) {

			int can_nocow;



			if (nowait && (ret == -ENOSPC || ret == -EAGAIN)) {

				ret = -EAGAIN;

				break;

			}



			/*

			 * If we don't have to COW at the offset, reserve

			 * metadata only. write_bytes may get smaller than

			 * requested here.

			 */

			can_nocow = btrfs_check_nocow_lock(BTRFS_I(inode), pos,

							   &write_bytes, nowait);

			if (can_nocow < 0)

				ret = can_nocow;

			if (can_nocow > 0)

				ret = 0;

			if (ret)

				break;

			only_release_metadata = true;

		}



		reserve_bytes = round_up(write_bytes + sector_offset,

					 fs_info->sectorsize);

		WARN_ON(reserve_bytes == 0);

		ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),

						      reserve_bytes,

						      reserve_bytes, nowait);

		if (ret) {

			if (!only_release_metadata)

				btrfs_free_reserved_data_space(BTRFS_I(inode),

						data_reserved, pos,

						write_bytes);

			else

				btrfs_check_nocow_unlock(BTRFS_I(inode));



			if (nowait && ret == -ENOSPC)

				ret = -EAGAIN;

		ret = reserve_space(BTRFS_I(inode), &data_reserved, pos,

				    &write_bytes, nowait, &only_release_metadata);

		if (ret < 0)

			break;

		}



		reserve_bytes = ret;

		release_bytes = reserve_bytes;

again:

		ret = balance_dirty_pages_ratelimited_flags(inode->i_mapping, bdp_flags);