[PATCH 3/4] btrfs: replace single page bio_iter_iovec() usage

[Qu Wenruo <wqu@suse.com>]

There are several functions inside btrfs calling bio_iter_iovec(),
mostly to do a block-by-block iteration on a bio.

- btrfs_check_read_bio()
- btrfs_decompress_buf2page()
- index_one_bio() from raid56

However that helper is single page based, meaning it will never return a
bv_len larger than PAGE_SIZE. For now it's fine as we only support bs <=
ps at most.

But for the incoming bs > ps support, we want to get bv_len larger than
PAGE_SIZE so that the bio_vec will cover a full block, not just part of
the large folio of the block.

In fact the call site inside btrfs_check_read_bio() will trigger
ASSERT() inside btrfs_data_csum_ok() when bs > ps support is enabled.
As bio_iter_iovec() will return a bv_len == 4K, meanwhile the bs is
larger than 4K, triggering the ASSERT().

Replace those call sites with mp_bvec_iter_bvec(), which will return the
full length of from the bi_io_vec array.
Currently all call sites are already doing extra loop inside the bvec
range for bs < ps support, so they will be fine.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/bio.c         | 3 ++-
 fs/btrfs/compression.c | 3 +--
 fs/btrfs/raid56.c      | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index ea7f7a17a3d5..f7aea4310dd6 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -277,8 +277,9 @@ static void btrfs_check_read_bio(struct btrfs_bio *bbio, struct btrfs_device *de
 	bbio->bio.bi_status = BLK_STS_OK;
 
 	while (iter->bi_size) {
-		struct bio_vec bv = bio_iter_iovec(&bbio->bio, *iter);
+		struct bio_vec bv = mp_bvec_iter_bvec(bbio->bio.bi_io_vec, *iter);
 
+		ASSERT(bv.bv_len >= sectorsize && IS_ALIGNED(bv.bv_len, sectorsize));
 		bv.bv_len = min(bv.bv_len, sectorsize);
 		if (status || !btrfs_data_csum_ok(bbio, dev, offset, &bv))
 			fbio = repair_one_sector(bbio, offset, &bv, fbio);
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 068339e86123..8b415c780ba8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1227,14 +1227,13 @@ int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
 	cur_offset = decompressed;
 	/* The main loop to do the copy */
 	while (cur_offset < decompressed + buf_len) {
-		struct bio_vec bvec;
+		struct bio_vec bvec = mp_bvec_iter_bvec(orig_bio->bi_io_vec, orig_bio->bi_iter);
 		size_t copy_len;
 		u32 copy_start;
 		/* Offset inside the full decompressed extent */
 		u32 bvec_offset;
 		void *kaddr;
 
-		bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
 		/*
 		 * cb->start may underflow, but subtracting that value can still
 		 * give us correct offset inside the full decompressed extent.
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 3ff2bedfb3a4..df48dd6c3f54 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1214,7 +1214,7 @@ static void index_one_bio(struct btrfs_raid_bio *rbio, struct bio *bio)
 	while (iter.bi_size) {
 		unsigned int index = (offset >> sectorsize_bits);
 		struct sector_ptr *sector = &rbio->bio_sectors[index];
-		struct bio_vec bv = bio_iter_iovec(bio, iter);
+		struct bio_vec bv = mp_bvec_iter_bvec(bio->bi_io_vec, iter);
 
 		sector->has_paddr = true;
 		sector->paddr = bvec_phys(&bv);
-- 
2.50.1