Commit 43fa4219 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: simplify adding pages in btrfs_add_compressed_bio_pages 



btrfs_add_compressed_bio_pages is needlessly complicated.  Instead
of iterating over the logic disk offset just to add pages to the bio
use a simple offset starting at 0, which also removes most of the
claiming.  Additionally __bio_add_pages already takes care of the
assert that the bio is always properly sized, and btrfs_submit_bio
called right after asserts that the bio size is non-zero.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 4513cb0c

fs/btrfs/compression.c

+7 −27
Original line number Diff line number Diff line
@@ -258,37 +258,17 @@ static void end_compressed_bio_write(struct btrfs_bio *bbio) 


static void btrfs_add_compressed_bio_pages(struct compressed_bio *cb)

{

	struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;

	struct bio *bio = &cb->bbio.bio;

	u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;

	u64 cur_disk_byte = disk_bytenr;

	u32 offset = 0;



	while (cur_disk_byte < disk_bytenr + cb->compressed_len) {

		u64 offset = cur_disk_byte - disk_bytenr;

		unsigned int index = offset >> PAGE_SHIFT;

		unsigned int real_size;

		unsigned int added;

		struct page *page = cb->compressed_pages[index];

	while (offset < cb->compressed_len) {

		u32 len = min_t(u32, cb->compressed_len - offset, PAGE_SIZE);



		/*

		 * We have various limit on the real read size:

		 * - page boundary

		 * - compressed length boundary

		 */

		real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));

		real_size = min_t(u64, real_size, cb->compressed_len - offset);

		ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));



		added = bio_add_page(bio, page, real_size, offset_in_page(offset));

		/*

		 * Maximum compressed extent is smaller than bio size limit,

		 * thus bio_add_page() should always success.

		 */

		ASSERT(added == real_size);

		cur_disk_byte += added;

		/* Maximum compressed extent is smaller than bio size limit. */

		__bio_add_page(bio, cb->compressed_pages[offset >> PAGE_SHIFT],

			       len, 0);

		offset += len;

	}



	ASSERT(bio->bi_iter.bi_size);

}



/*