btrfs: remove stripe boundary calculation for compressed I/O

Stop looking at the stripe boundary in alloc_compressed_bio() now that
that btrfs_submit_bio can split bios, open code the now trivial code
from alloc_compressed_bio() in btrfs_submit_compressed_read and stop
maintaining the pending_ios count for reads as there is always just
a single bio now.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
[hch: remove more cruft in btrfs_submit_compressed_read,
      use btrfs_zoned_get_device in alloc_compressed_bio]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -141,12 +141,15 @@ static int compression_decompress(int type, struct list_head *ws,
 
 static int btrfs_decompress_bio(struct compressed_bio *cb);
 
-static void finish_compressed_bio_read(struct compressed_bio *cb)
+static void end_compressed_bio_read(struct btrfs_bio *bbio)
 {
+	struct compressed_bio *cb = bbio->private;
 	unsigned int index;
 	struct page *page;
 
-	if (cb->status == BLK_STS_OK)
+	if (bbio->bio.bi_status)
+		cb->status = bbio->bio.bi_status;
+	else
 		cb->status = errno_to_blk_status(btrfs_decompress_bio(cb));
 
 	/* Release the compressed pages */
@@ -162,17 +165,6 @@ static void finish_compressed_bio_read(struct compressed_bio *cb)
 	/* Finally free the cb struct */
 	kfree(cb->compressed_pages);
 	kfree(cb);
-}
-
-static void end_compressed_bio_read(struct btrfs_bio *bbio)
-{
-	struct compressed_bio *cb = bbio->private;
-
-	if (bbio->bio.bi_status)
-		cb->status = bbio->bio.bi_status;
-
-	if (refcount_dec_and_test(&cb->pending_ios))
-		finish_compressed_bio_read(cb);
 	bio_put(&bbio->bio);
 }
 
@@ -289,43 +281,30 @@ static void end_compressed_bio_write(struct btrfs_bio *bbio)
  *                      from or written to.
  * @endio_func:         The endio function to call after the IO for compressed data
  *                      is finished.
- * @next_stripe_start:  Return value of logical bytenr of where next stripe starts.
- *                      Let the caller know to only fill the bio up to the stripe
- *                      boundary.
  */
-
-
 static struct bio *alloc_compressed_bio(struct compressed_bio *cb, u64 disk_bytenr,
 					blk_opf_t opf,
-					btrfs_bio_end_io_t endio_func,
-					u64 *next_stripe_start)
+					btrfs_bio_end_io_t endio_func)
 {
-	struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
-	struct btrfs_io_geometry geom;
-	struct extent_map *em;
 	struct bio *bio;
-	int ret;
 
 	bio = btrfs_bio_alloc(BIO_MAX_VECS, opf, BTRFS_I(cb->inode), endio_func,
 			      cb);
 	bio->bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
 
-	em = btrfs_get_chunk_map(fs_info, disk_bytenr, fs_info->sectorsize);
-	if (IS_ERR(em)) {
+	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(em);
+			return ERR_CAST(device);
 		}
 
-	if (bio_op(bio) == REQ_OP_ZONE_APPEND)
-		bio_set_dev(bio, em->map_lookup->stripes[0].dev->bdev);
-
-	ret = btrfs_get_io_geometry(fs_info, em, btrfs_op(bio), disk_bytenr, &geom);
-	free_extent_map(em);
-	if (ret < 0) {
-		bio_put(bio);
-		return ERR_PTR(ret);
+		bio_set_dev(bio, device->bdev);
 	}
-	*next_stripe_start = disk_bytenr + geom.len;
 	refcount_inc(&cb->pending_ios);
 	return bio;
 }
@@ -352,7 +331,6 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	struct bio *bio = NULL;
 	struct compressed_bio *cb;
 	u64 cur_disk_bytenr = disk_start;
-	u64 next_stripe_start;
 	blk_status_t ret = BLK_STS_OK;
 	const bool use_append = btrfs_use_zone_append(inode, disk_start);
 	const enum req_op bio_op = REQ_BTRFS_ONE_ORDERED |
@@ -388,8 +366,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 		/* Allocate new bio if submitted or not yet allocated */
 		if (!bio) {
 			bio = alloc_compressed_bio(cb, cur_disk_bytenr,
-				bio_op | write_flags, end_compressed_bio_write,
-				&next_stripe_start);
+				bio_op | write_flags, end_compressed_bio_write);
 			if (IS_ERR(bio)) {
 				ret = errno_to_blk_status(PTR_ERR(bio));
 				break;
@@ -398,20 +375,12 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 			if (blkcg_css)
 				bio->bi_opf |= REQ_CGROUP_PUNT;
 		}
-		/*
-		 * We should never reach next_stripe_start start as we will
-		 * submit comp_bio when reach the boundary immediately.
-		 */
-		ASSERT(cur_disk_bytenr != next_stripe_start);
-
 		/*
 		 * We have various limits on the real read size:
-		 * - stripe boundary
 		 * - page boundary
 		 * - compressed length boundary
 		 */
-		real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_bytenr);
-		real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
+		real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));
 		real_size = min_t(u64, real_size, compressed_len - offset);
 		ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
 
@@ -426,9 +395,6 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 			submit = true;
 
 		cur_disk_bytenr += added;
-		/* Reached stripe boundary */
-		if (cur_disk_bytenr == next_stripe_start)
-			submit = true;
 
 		/* Finished the range */
 		if (cur_disk_bytenr == disk_start + compressed_len)
@@ -623,10 +589,9 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	struct extent_map_tree *em_tree;
 	struct compressed_bio *cb;
 	unsigned int compressed_len;
-	struct bio *comp_bio = NULL;
+	struct bio *comp_bio;
 	const u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
 	u64 cur_disk_byte = disk_bytenr;
-	u64 next_stripe_start;
 	u64 file_offset;
 	u64 em_len;
 	u64 em_start;
@@ -693,37 +658,23 @@ void 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, REQ_OP_READ, BTRFS_I(cb->inode),
+				   end_compressed_bio_read, cb);
+	comp_bio->bi_iter.bi_sector = (cur_disk_byte >> SECTOR_SHIFT);
+
 	while (cur_disk_byte < disk_bytenr + 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];
-		bool submit = false;
 
-		/* Allocate new bio if submitted or not yet allocated */
-		if (!comp_bio) {
-			comp_bio = alloc_compressed_bio(cb, cur_disk_byte,
-					REQ_OP_READ, end_compressed_bio_read,
-					&next_stripe_start);
-			if (IS_ERR(comp_bio)) {
-				cb->status = errno_to_blk_status(PTR_ERR(comp_bio));
-				break;
-			}
-		}
-		/*
-		 * We should never reach next_stripe_start start as we will
-		 * submit comp_bio when reach the boundary immediately.
-		 */
-		ASSERT(cur_disk_byte != next_stripe_start);
 		/*
 		 * We have various limit on the real read size:
-		 * - stripe boundary
 		 * - page boundary
 		 * - compressed length boundary
 		 */
-		real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_byte);
-		real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
+		real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));
 		real_size = min_t(u64, real_size, compressed_len - offset);
 		ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
 
@@ -734,35 +685,20 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		 */
 		ASSERT(added == real_size);
 		cur_disk_byte += added;
+	}
 
-		/* Reached stripe boundary, need to submit */
-		if (cur_disk_byte == next_stripe_start)
-			submit = true;
-
-		/* Has finished the range, need to submit */
-		if (cur_disk_byte == disk_bytenr + compressed_len)
-			submit = true;
+	if (memstall)
+		psi_memstall_leave(&pflags);
 
-		if (submit) {
 	/*
-			 * Save the initial offset of this chunk, as there
-			 * is no direct correlation between compressed pages and
-			 * the original file offset.  The field is only used for
-			 * printing error messages.
+	 * Stash the initial offset of this chunk, as there is no direct
+	 * correlation between compressed pages and the original file offset.
+	 * The field is only used for printing error messages anyway.
 	 */
 	btrfs_bio(comp_bio)->file_offset = file_offset;
 
 	ASSERT(comp_bio->bi_iter.bi_size);
 	btrfs_submit_bio(fs_info, comp_bio, mirror_num);
-			comp_bio = NULL;
-		}
-	}
-
-	if (memstall)
-		psi_memstall_leave(&pflags);
-
-	if (refcount_dec_and_test(&cb->pending_ios))
-		finish_compressed_bio_read(cb);
 	return;
 
 fail: