btrfs: introduce btrfs_bio_for_each_block_all() helper

Currently if we want to iterate all blocks inside a bio, we do something
like this:

	bio_for_each_segment_all(bvec, bio, iter_all) {
		for (off = 0; off < bvec->bv_len; off += sectorsize) {
			/* Iterate blocks using bv + off */
		}
	}

That's fine for now, but it will not handle future bs > ps, as
bio_for_each_segment_all() is a single-page iterator, it will always
return a bvec that's no larger than a page.

But for bs > ps cases, we need a full folio (which covers at least one
block) so that we can work on the block.

To address this problem and handle future bs > ps cases better:

- Introduce a helper btrfs_bio_for_each_block_all()
  This helper will create a local bvec_iter, which has the size of the
  target bio. Then grab the current physical address of the current
  location, then advance the iterator by block size.

- Use btrfs_bio_for_each_block_all() to replace existing call sites
  Including:

  * set_bio_pages_uptodate() in raid56
  * verify_bio_data_sectors() in raid56

  Both will result much easier to read code.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

2 files changed, 44 insertions, 29 deletions

diff --git a/fs/btrfs/misc.h b/fs/btrfs/misc.h
index f8f055fdc551..60f9b000d644 100644
--- a/fs/btrfs/misc.h
+++ b/fs/btrfs/misc.h
@@ -45,6 +45,30 @@ static inline phys_addr_t bio_iter_phys(struct bio *bio, struct bvec_iter *iter)
 	     (paddr = bio_iter_phys((bio), (iter)), 1);			\
 	     bio_advance_iter_single((bio), (iter), (blocksize)))
 
+/* Initialize a bvec_iter to the size of the specified bio. */
+static inline struct bvec_iter init_bvec_iter_for_bio(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	u32 bio_size = 0;
+	int i;
+
+	bio_for_each_bvec_all(bvec, bio, i)
+		bio_size += bvec->bv_len;
+
+	return (struct bvec_iter) {
+		.bi_sector = 0,
+		.bi_size = bio_size,
+		.bi_idx = 0,
+		.bi_bvec_done = 0,
+	};
+}
+
+#define btrfs_bio_for_each_block_all(paddr, bio, blocksize)		\
+	for (struct bvec_iter iter = init_bvec_iter_for_bio(bio);	\
+	     (iter).bi_size &&						\
+	     (paddr = bio_iter_phys((bio), &(iter)), 1);		\
+	     bio_advance_iter_single((bio), &(iter), (blocksize)))
+
 static inline void cond_wake_up(struct wait_queue_head *wq)
 {
 	/*
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 389f1b617fe7..2b4f577dcf39 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1510,22 +1510,17 @@ static struct sector_ptr *find_stripe_sector(struct btrfs_raid_bio *rbio,
  */
 static void set_bio_pages_uptodate(struct btrfs_raid_bio *rbio, struct bio *bio)
 {
-	const u32 sectorsize = rbio->bioc->fs_info->sectorsize;
-	struct bio_vec *bvec;
-	struct bvec_iter_all iter_all;
+	const u32 blocksize = rbio->bioc->fs_info->sectorsize;
+	phys_addr_t paddr;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
 
-	bio_for_each_segment_all(bvec, bio, iter_all) {
-		struct sector_ptr *sector;
-		phys_addr_t paddr = bvec_phys(bvec);
+	btrfs_bio_for_each_block_all(paddr, bio, blocksize) {
+		struct sector_ptr *sector = find_stripe_sector(rbio, paddr);
 
-		for (u32 off = 0; off < bvec->bv_len; off += sectorsize) {
-			sector = find_stripe_sector(rbio, paddr + off);
-			ASSERT(sector);
-			if (sector)
-				sector->uptodate = 1;
-		}
+		ASSERT(sector);
+		if (sector)
+			sector->uptodate = 1;
 	}
 }
 
@@ -1572,8 +1567,7 @@ static void verify_bio_data_sectors(struct btrfs_raid_bio *rbio,
 {
 	struct btrfs_fs_info *fs_info = rbio->bioc->fs_info;
 	int total_sector_nr = get_bio_sector_nr(rbio, bio);
-	struct bio_vec *bvec;
-	struct bvec_iter_all iter_all;
+	phys_addr_t paddr;
 
 	/* No data csum for the whole stripe, no need to verify. */
 	if (!rbio->csum_bitmap || !rbio->csum_buf)
@@ -1583,23 +1577,20 @@ static void verify_bio_data_sectors(struct btrfs_raid_bio *rbio,
 	if (total_sector_nr >= rbio->nr_data * rbio->stripe_nsectors)
 		return;
 
-	bio_for_each_segment_all(bvec, bio, iter_all) {
-		for (u32 off = 0; off < bvec->bv_len;
-		     off += fs_info->sectorsize, total_sector_nr++) {
-			u8 csum_buf[BTRFS_CSUM_SIZE];
-			u8 *expected_csum = rbio->csum_buf +
-					    total_sector_nr * fs_info->csum_size;
-			int ret;
+	btrfs_bio_for_each_block_all(paddr, bio, fs_info->sectorsize) {
+		u8 csum_buf[BTRFS_CSUM_SIZE];
+		u8 *expected_csum = rbio->csum_buf + total_sector_nr * fs_info->csum_size;
+		int ret;
 
-			/* No csum for this sector, skip to the next sector. */
-			if (!test_bit(total_sector_nr, rbio->csum_bitmap))
-				continue;
+		/* No csum for this sector, skip to the next sector. */
+		if (!test_bit(total_sector_nr, rbio->csum_bitmap))
+			continue;
 
-			ret = btrfs_check_block_csum(fs_info, bvec_phys(bvec) + off,
-						     csum_buf, expected_csum);
-			if (ret < 0)
-				set_bit(total_sector_nr, rbio->error_bitmap);
-		}
+		ret = btrfs_check_block_csum(fs_info, paddr,
+					     csum_buf, expected_csum);
+		if (ret < 0)
+			set_bit(total_sector_nr, rbio->error_bitmap);
+		total_sector_nr++;
 	}
 }