[PATCH 5.12 038/127] btrfs: zoned: fix parallel compressed writes

Greg Kroah-Hartman
2021-05-24T16:04:25Z

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

commit 764c7c9a464b68f7c6a5a9ec0b923176a05e8e8f upstream.

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: David Sterba <dsterba@suse.com>
Fixes: 9d294a685fbc ("btrfs: zoned: enable to mount ZONED incompat flag")
CC: stable@vger.kernel.org # 5.12.x: e380adfc213a13: btrfs: zoned: pass start block to btrfs_use_zone_append
CC: stable@vger.kernel.org # 5.12.x
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/compression.c | 42 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)

--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -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(str
*/
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_wri
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_wri
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_wri
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_wri
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_wri
}

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) {