btrfs: introduce alloc_compressed_bio() for compression

Just aggregate the bio allocation code into one helper, so that we can
replace 4 call sites.

There is one special note for zoned write.

Currently btrfs_submit_compressed_write() will only allocate the first
bio using ZONE_APPEND.  If we have to submit current bio due to stripe
boundary, the new bio allocated will not use ZONE_APPEND.

In theory this should be a bug, but considering zoned mode currently
only support SINGLE profile, which doesn't have any stripe boundary
limit, it should never be a problem and we have assertions in place.

This function will provide a good entrance for any work which needs to
be done at bio allocation time. Like determining the stripe boundary.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -434,6 +434,36 @@ static blk_status_t submit_compressed_bio(struct btrfs_fs_info *fs_info,
 	return ret;
 }
 
+/*
+ * Allocate a compressed_bio, which will be used to read/write on-disk data.
+ */
+static struct bio *alloc_compressed_bio(struct compressed_bio *cb, u64 disk_bytenr,
+					unsigned int opf, bio_end_io_t endio_func)
+{
+	struct bio *bio;
+
+	bio = btrfs_bio_alloc(BIO_MAX_VECS);
+
+	bio->bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
+	bio->bi_opf = opf;
+	bio->bi_private = cb;
+	bio->bi_end_io = endio_func;
+
+	if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
+		struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
+		struct btrfs_device *device;
+
+		device = btrfs_zoned_get_device(fs_info, disk_bytenr,
+						fs_info->sectorsize);
+		if (IS_ERR(device)) {
+			bio_put(bio);
+			return ERR_CAST(device);
+		}
+		bio_set_dev(bio, device->bdev);
+	}
+	return bio;
+}
+
 /*
  * worker function to build and submit bios for previously compressed pages.
  * The corresponding pages in the inode should be marked for writeback
@@ -479,23 +509,11 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	cb->orig_bio = NULL;
 	cb->nr_pages = nr_pages;
 
-	bio = btrfs_bio_alloc(BIO_MAX_VECS);
-	bio->bi_iter.bi_sector = first_byte >> SECTOR_SHIFT;
-	bio->bi_opf = bio_op | write_flags;
-	bio->bi_private = cb;
-	bio->bi_end_io = end_compressed_bio_write;
-
-	if (use_append) {
-		struct btrfs_device *device;
-
-		device = btrfs_zoned_get_device(fs_info, disk_start, PAGE_SIZE);
-		if (IS_ERR(device)) {
+	bio = alloc_compressed_bio(cb, first_byte, bio_op | write_flags,
+				   end_compressed_bio_write);
+	if (IS_ERR(bio)) {
 		kfree(cb);
-			bio_put(bio);
-			return BLK_STS_NOTSUPP;
-		}
-
-		bio_set_dev(bio, device->bdev);
+		return errno_to_blk_status(PTR_ERR(bio));
 	}
 
 	if (blkcg_css) {
@@ -539,11 +557,14 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 			if (ret)
 				goto finish_cb;
 
-			bio = btrfs_bio_alloc(BIO_MAX_VECS);
-			bio->bi_iter.bi_sector = first_byte >> SECTOR_SHIFT;
-			bio->bi_opf = bio_op | write_flags;
-			bio->bi_private = cb;
-			bio->bi_end_io = end_compressed_bio_write;
+			bio = alloc_compressed_bio(cb, first_byte,
+					bio_op | write_flags,
+					end_compressed_bio_write);
+			if (IS_ERR(bio)) {
+				ret = errno_to_blk_status(PTR_ERR(bio));
+				bio = NULL;
+				goto finish_cb;
+			}
 			if (blkcg_css)
 				bio->bi_opf |= REQ_CGROUP_PUNT;
 			/*
@@ -839,11 +860,13 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	/* include any pages we added in add_ra-bio_pages */
 	cb->len = bio->bi_iter.bi_size;
 
-	comp_bio = btrfs_bio_alloc(BIO_MAX_VECS);
-	comp_bio->bi_iter.bi_sector = cur_disk_byte >> SECTOR_SHIFT;
-	comp_bio->bi_opf = REQ_OP_READ;
-	comp_bio->bi_private = cb;
-	comp_bio->bi_end_io = end_compressed_bio_read;
+	comp_bio = alloc_compressed_bio(cb, cur_disk_byte, REQ_OP_READ,
+					end_compressed_bio_read);
+	if (IS_ERR(comp_bio)) {
+		ret = errno_to_blk_status(PTR_ERR(comp_bio));
+		comp_bio = NULL;
+		goto fail2;
+	}
 
 	for (pg_index = 0; pg_index < nr_pages; pg_index++) {
 		u32 pg_len = PAGE_SIZE;
@@ -884,11 +907,14 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			if (ret)
 				goto finish_cb;
 
-			comp_bio = btrfs_bio_alloc(BIO_MAX_VECS);
-			comp_bio->bi_iter.bi_sector = cur_disk_byte >> SECTOR_SHIFT;
-			comp_bio->bi_opf = REQ_OP_READ;
-			comp_bio->bi_private = cb;
-			comp_bio->bi_end_io = end_compressed_bio_read;
+			comp_bio = alloc_compressed_bio(cb, cur_disk_byte,
+					REQ_OP_READ,
+					end_compressed_bio_read);
+			if (IS_ERR(comp_bio)) {
+				ret = errno_to_blk_status(PTR_ERR(comp_bio));
+				comp_bio = NULL;
+				goto finish_cb;
+			}
 
 			bio_add_page(comp_bio, page, pg_len, 0);
 		}