btrfs: limit write bios to a single ordered extent

Currently buffered writeback bios are allowed to span multiple
ordered_extents, although that basically never actually happens since
commit 4a445b7b ("btrfs: don't merge pages into bio if their page
offset is not contiguous").

Supporting bios than span ordered_extents complicates the file
checksumming code, and prevents us from adding an ordered_extent pointer
to the btrfs_bio structure.  Use the existing code to limit a bio to
single ordered_extent for zoned device writes for all writes.

This allows to remove the REQ_BTRFS_ONE_ORDERED flags, and the
handling of multiple ordered_extents in btrfs_csum_one_bio.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/bio.c

@@ -457,9 +457,6 @@ static void btrfs_submit_mirrored_bio(struct btrfs_io_context *bioc, int dev_nr)
 static void __btrfs_submit_bio(struct bio *bio, struct btrfs_io_context *bioc,
 			       struct btrfs_io_stripe *smap, int mirror_num)
 {
-	/* Do not leak our private flag into the block layer. */
-	bio->bi_opf &= ~REQ_BTRFS_ONE_ORDERED;
-
 	if (!bioc) {
 		/* Single mirror read/write fast path. */
 		btrfs_bio(bio)->mirror_num = mirror_num;

fs/btrfs/bio.h

@@ -102,9 +102,6 @@ static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 	bbio->end_io(bbio);
 }
 
-/* Bio only refers to one ordered extent. */
-#define REQ_BTRFS_ONE_ORDERED			REQ_DRV
-
 /* Submit using blkcg_punt_bio_submit. */
 #define REQ_BTRFS_CGROUP_PUNT			REQ_FS_PRIVATE
 

fs/btrfs/compression.c

@@ -293,8 +293,6 @@ void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
 	       IS_ALIGNED(len, fs_info->sectorsize));
 
-	write_flags |= REQ_BTRFS_ONE_ORDERED;
-
 	cb = alloc_compressed_bio(inode, start, REQ_OP_WRITE | write_flags,
 				  end_compressed_bio_write);
 	cb->start = start;

fs/btrfs/extent_io.c

@@ -826,13 +826,8 @@ static void alloc_new_bio(struct btrfs_inode *inode,
 	bio_ctrl->bbio = bbio;
 	bio_ctrl->len_to_oe_boundary = U32_MAX;
 
-	/*
-	 * Limit the extent to the ordered boundary for Zone Append.
-	 * Compressed bios aren't submitted directly, so it doesn't apply to
-	 * them.
-	 */
-	if (bio_ctrl->compress_type == BTRFS_COMPRESS_NONE &&
-	    btrfs_use_zone_append(bbio)) {
+	/* Limit data write bios to the ordered boundary. */
+	if (bio_ctrl->wbc) {
 		struct btrfs_ordered_extent *ordered;
 
 		ordered = btrfs_lookup_ordered_extent(inode, file_offset);
@@ -842,9 +837,7 @@ static void alloc_new_bio(struct btrfs_inode *inode,
 					ordered->disk_num_bytes - file_offset);
 			btrfs_put_ordered_extent(ordered);
 		}
-	}
 
-	if (bio_ctrl->wbc) {
 		/*
 		 * Pick the last added device to support cgroup writeback.  For
 		 * multi-device file systems this means blk-cgroup policies have

fs/btrfs/file-item.c

@@ -733,8 +733,6 @@ blk_status_t btrfs_csum_one_bio(struct btrfs_bio *bbio)
 	struct bio_vec bvec;
 	int index;
 	unsigned int blockcount;
-	unsigned long total_bytes = 0;
-	unsigned long this_sum_bytes = 0;
 	int i;
 	unsigned nofs_flag;
 
@@ -776,34 +774,6 @@ blk_status_t btrfs_csum_one_bio(struct btrfs_bio *bbio)
 						 - 1);
 
 		for (i = 0; i < blockcount; i++) {
-			if (!(bio->bi_opf & REQ_BTRFS_ONE_ORDERED) &&
-			    !in_range(offset, ordered->file_offset,
-				      ordered->num_bytes)) {
-				unsigned long bytes_left;
-
-				sums->len = this_sum_bytes;
-				this_sum_bytes = 0;
-				btrfs_add_ordered_sum(ordered, sums);
-				btrfs_put_ordered_extent(ordered);
-
-				bytes_left = bio->bi_iter.bi_size - total_bytes;
-
-				nofs_flag = memalloc_nofs_save();
-				sums = kvzalloc(btrfs_ordered_sum_size(fs_info,
-						      bytes_left), GFP_KERNEL);
-				memalloc_nofs_restore(nofs_flag);
-				if (!sums)
-					return BLK_STS_RESOURCE;
-
-				sums->len = bytes_left;
-				ordered = btrfs_lookup_ordered_extent(inode,
-								offset);
-				ASSERT(ordered); /* Logic error */
-				sums->logical = (bio->bi_iter.bi_sector << SECTOR_SHIFT)
-					+ total_bytes;
-				index = 0;
-			}
-
 			data = bvec_kmap_local(&bvec);
 			crypto_shash_digest(shash,
 					    data + (i * fs_info->sectorsize),
@@ -812,18 +782,10 @@ blk_status_t btrfs_csum_one_bio(struct btrfs_bio *bbio)
 			kunmap_local(data);
 			index += fs_info->csum_size;
 			offset += fs_info->sectorsize;
-			this_sum_bytes += fs_info->sectorsize;
-			total_bytes += fs_info->sectorsize;
 		}
 
 	}
-	this_sum_bytes = 0;
 
-	/*
-	 * The ->sums assignment is for zoned writes, where a bio never spans
-	 * ordered extents and is only done unconditionally because that's cheaper
-	 * than a branch.
-	 */
 	bbio->sums = sums;
 	btrfs_add_ordered_sum(ordered, sums);
 	btrfs_put_ordered_extent(ordered);