Commit 764c7c9a authored by Johannes Thumshirn's avatar Johannes Thumshirn Committed by David Sterba
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btrfs: zoned: fix parallel compressed writes 



When multiple processes write data to the same block group on a
compressed zoned filesystem, the underlying device could report I/O
errors and data corruption is possible.

This happens because on a zoned file system, compressed data writes
where sent to the device via a REQ_OP_WRITE instead of a
REQ_OP_ZONE_APPEND operation. But with REQ_OP_WRITE and parallel
submission it cannot be guaranteed that the data is always submitted
aligned to the underlying zone's write pointer.

The change to using REQ_OP_ZONE_APPEND instead of REQ_OP_WRITE on a
zoned filesystem is non intrusive on a regular file system or when
submitting to a conventional zone on a zoned filesystem, as it is
guarded by btrfs_use_zone_append.

Reported-by: default avatarDavid Sterba <dsterba@suse.com>
Fixes: 9d294a68 ("btrfs: zoned: enable to mount ZONED incompat flag")
CC: stable@vger.kernel.org # 5.12.x: e380adfc: btrfs: zoned: pass start block to btrfs_use_zone_append
CC: stable@vger.kernel.org # 5.12.x
Signed-off-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e380adfc

fs/btrfs/compression.c

+38 −4
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include "compression.h"

#include "extent_io.h"

#include "extent_map.h"

#include "zoned.h"



static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
@@ -349,6 +350,7 @@ static void end_compressed_bio_write(struct bio *bio) 
	 */

	inode = cb->inode;

	cb->compressed_pages[0]->mapping = cb->inode->i_mapping;

	btrfs_record_physical_zoned(inode, cb->start, bio);

	btrfs_writepage_endio_finish_ordered(cb->compressed_pages[0],

			cb->start, cb->start + cb->len - 1,

			bio->bi_status == BLK_STS_OK);
@@ -401,6 +403,8 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 
	u64 first_byte = disk_start;

	blk_status_t ret;

	int skip_sum = inode->flags & BTRFS_INODE_NODATASUM;

	const bool use_append = btrfs_use_zone_append(inode, disk_start);

	const unsigned int bio_op = use_append ? REQ_OP_ZONE_APPEND : REQ_OP_WRITE;



	WARN_ON(!PAGE_ALIGNED(start));

	cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
@@ -418,10 +422,31 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 
	cb->nr_pages = nr_pages;



	bio = btrfs_bio_alloc(first_byte);

	bio->bi_opf = REQ_OP_WRITE | write_flags;

	bio->bi_opf = bio_op | write_flags;

	bio->bi_private = cb;

	bio->bi_end_io = end_compressed_bio_write;



	if (use_append) {

		struct extent_map *em;

		struct map_lookup *map;

		struct block_device *bdev;



		em = btrfs_get_chunk_map(fs_info, disk_start, PAGE_SIZE);

		if (IS_ERR(em)) {

			kfree(cb);

			bio_put(bio);

			return BLK_STS_NOTSUPP;

		}



		map = em->map_lookup;

		/* We only support single profile for now */

		ASSERT(map->num_stripes == 1);

		bdev = map->stripes[0].dev->bdev;



		bio_set_dev(bio, bdev);

		free_extent_map(em);

	}



	if (blkcg_css) {

		bio->bi_opf |= REQ_CGROUP_PUNT;

		kthread_associate_blkcg(blkcg_css);
@@ -432,6 +457,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 
	bytes_left = compressed_len;

	for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {

		int submit = 0;

		int len;



		page = compressed_pages[pg_index];

		page->mapping = inode->vfs_inode.i_mapping;
@@ -439,9 +465,13 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 
			submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,

							  0);



		if (pg_index == 0 && use_append)

			len = bio_add_zone_append_page(bio, page, PAGE_SIZE, 0);

		else

			len = bio_add_page(bio, page, PAGE_SIZE, 0);



		page->mapping = NULL;

		if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <

		    PAGE_SIZE) {

		if (submit || len < PAGE_SIZE) {

			/*

			 * inc the count before we submit the bio so

			 * we know the end IO handler won't happen before
@@ -465,11 +495,15 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 
			}



			bio = btrfs_bio_alloc(first_byte);

			bio->bi_opf = REQ_OP_WRITE | write_flags;

			bio->bi_opf = bio_op | write_flags;

			bio->bi_private = cb;

			bio->bi_end_io = end_compressed_bio_write;

			if (blkcg_css)

				bio->bi_opf |= REQ_CGROUP_PUNT;

			/*

			 * Use bio_add_page() to ensure the bio has at least one

			 * page.

			 */

			bio_add_page(bio, page, PAGE_SIZE, 0);

		}

		if (bytes_left < PAGE_SIZE) {