Commit eefa45f5 authored by Goldwyn Rodrigues's avatar Goldwyn Rodrigues Committed by David Sterba
Browse files

btrfs: calculate num_pages, reserve_bytes once in btrfs_buffered_write 



write_bytes can change in btrfs_check_nocow_lock(). Calculate variables
such as num_pages and reserve_bytes once we are sure of the value of
write_bytes so there is no need to re-calculate.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent fb8a7e94

fs/btrfs/file.c

+12 −22
Original line number Diff line number Diff line
@@ -1591,8 +1591,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, 
		size_t write_bytes = min(iov_iter_count(i),

					 nrptrs * (size_t)PAGE_SIZE -

					 offset);

		size_t num_pages = DIV_ROUND_UP(write_bytes + offset,

						PAGE_SIZE);

		size_t num_pages;

		size_t reserve_bytes;

		size_t dirty_pages;

		size_t copied;
@@ -1600,8 +1599,6 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, 
		size_t num_sectors;

		int extents_locked;



		WARN_ON(num_pages > nrptrs);



		/*

		 * Fault pages before locking them in prepare_pages

		 * to avoid recursive lock
@@ -1613,35 +1610,28 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb, 


		only_release_metadata = false;

		sector_offset = pos & (fs_info->sectorsize - 1);

		reserve_bytes = round_up(write_bytes + sector_offset,

				fs_info->sectorsize);



		extent_changeset_release(data_reserved);

		ret = btrfs_check_data_free_space(BTRFS_I(inode),

						  &data_reserved, pos,

						  write_bytes);

		if (ret < 0) {

			if (btrfs_check_nocow_lock(BTRFS_I(inode), pos,

						   &write_bytes) > 0) {

			/*

				 * For nodata cow case, no need to reserve

				 * data space.

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

			 * metadata only. write_bytes may get smaller than

			 * requested here.

			 */

			if (btrfs_check_nocow_lock(BTRFS_I(inode), pos,

						   &write_bytes) > 0)

				only_release_metadata = true;

				/*

				 * our prealloc extent may be smaller than

				 * write_bytes, so scale down.

				 */

				num_pages = DIV_ROUND_UP(write_bytes + offset,

							 PAGE_SIZE);

				reserve_bytes = round_up(write_bytes +

							 sector_offset,

							 fs_info->sectorsize);

			} else {

			else

				break;

		}

		}



		num_pages = DIV_ROUND_UP(write_bytes + offset, PAGE_SIZE);

		WARN_ON(num_pages > nrptrs);

		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);