[PATCH v3 RESEND 3/4] btrfs: use a shared helper to calculate data checksum for a bio

[Qu Wenruo <wqu@suse.com>]

Since we are already calculating data checksum using bio interface,
extract the generation part into btrfs_csum_one_bio_block(), and use that
to replace the paddrs[] array based solution in csum_one_bio().

This will reduce 128 bytes on-stack memory usage for csum_one_bio().

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/btrfs_inode.h |  2 ++
 fs/btrfs/file-item.c   | 20 ++++++------------
 fs/btrfs/inode.c       | 46 +++++++++++++++++++++++++-----------------
 3 files changed, 35 insertions(+), 33 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index d5a5c79ea6fb..6d02964da8ed 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -515,6 +515,8 @@ int btrfs_check_block_csum(struct btrfs_fs_info *fs_info, phys_addr_t paddr, u8
 			   const u8 * const csum_expected);
 bool btrfs_bio_data_csum_ok(struct btrfs_bio *bbio, const struct bvec_iter *orig_iter,
 			    struct btrfs_device *dev);
+void btrfs_csum_one_bio_block(struct btrfs_fs_info *fs_info, struct bio *bio,
+			      const struct bvec_iter *orig_iter, u8 *csum);
 noinline int can_nocow_extent(struct btrfs_inode *inode, u64 offset, u64 *len,
 			      struct btrfs_file_extent *file_extent,
 			      bool nowait);
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index cf50fd623f41..72ebd7c9ef10 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -801,25 +801,17 @@ static void csum_one_bio(struct btrfs_bio *bbio, struct bvec_iter *src)
 {
 	struct btrfs_inode *inode = bbio->inode;
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	struct bio *bio = &bbio->bio;
 	struct btrfs_ordered_sum *sums = bbio->sums;
-	struct bvec_iter iter = *src;
-	phys_addr_t paddr;
+	struct bvec_iter iter;
 	const u32 blocksize = fs_info->sectorsize;
-	const u32 step = min(blocksize, PAGE_SIZE);
-	const u32 nr_steps = blocksize / step;
-	phys_addr_t paddrs[BTRFS_MAX_BLOCKSIZE / PAGE_SIZE];
-	u32 offset = 0;
 	int index = 0;
 
-	btrfs_bio_for_each_block(paddr, bio, &iter, step) {
-		paddrs[(offset / step) % nr_steps] = paddr;
-		offset += step;
+	for (iter = *src; iter.bi_size;
+	     bio_advance_iter(&bbio->bio, &iter, blocksize)) {
+		btrfs_csum_one_bio_block(fs_info, &bbio->bio, &iter,
+					 sums->sums + index);
 
-		if (IS_ALIGNED(offset, blocksize)) {
-			btrfs_calculate_block_csum_pages(fs_info, paddrs, sums->sums + index);
-			index += fs_info->csum_size;
-		}
+		index += fs_info->csum_size;
 	}
 }
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 370899992d5d..15c80f3f53d7 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3531,6 +3531,32 @@ int btrfs_check_block_csum(struct btrfs_fs_info *fs_info, phys_addr_t paddr, u8
 	return 0;
 }
 
+/* Generate data checksum for a single fs block, pointed by @orig_iter. */
+void btrfs_csum_one_bio_block(struct btrfs_fs_info *fs_info, struct bio *bio,
+			      const struct bvec_iter *orig_iter, u8 *csum)
+{
+	struct btrfs_csum_ctx cctx;
+	struct bvec_iter iter = *orig_iter;
+	const u32 blocksize = fs_info->sectorsize;
+	u32 cur = 0;
+
+	btrfs_csum_init(&cctx, fs_info->csum_type);
+	while (cur < blocksize) {
+		struct page *page = bio_iter_page(bio, iter);
+		const u32 pg_off = bio_iter_offset(bio, iter);
+		const u32 cur_len = min(bio_iter_len(bio, iter), blocksize - cur);
+		void *kaddr;
+
+		kaddr = kmap_local_page(page) + pg_off;
+		btrfs_csum_update(&cctx, kaddr, cur_len);
+		kunmap_local(kaddr);
+
+		bio_advance_iter_single(bio, &iter, cur_len);
+		cur += cur_len;
+	}
+	btrfs_csum_final(&cctx, csum);
+}
+
 /*
  * Verify the checksum of a single data sector, which can be scattered at
  * different noncontiguous pages.
@@ -3551,7 +3577,6 @@ bool btrfs_bio_data_csum_ok(struct btrfs_bio *bbio,
 	struct btrfs_inode *inode = bbio->inode;
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct bvec_iter iter = *orig_iter;
-	struct btrfs_csum_ctx cctx;
 	const u32 blocksize = fs_info->sectorsize;
 	const u32 bio_offset = (iter.bi_sector - bbio->saved_iter.bi_sector) << SECTOR_SHIFT;
 	u64 file_offset = bbio->file_offset + bio_offset;
@@ -3576,22 +3601,7 @@ bool btrfs_bio_data_csum_ok(struct btrfs_bio *bbio,
 
 	csum_expected = bbio->csum + (bio_offset >> fs_info->sectorsize_bits) *
 				fs_info->csum_size;
-	btrfs_csum_init(&cctx, fs_info->csum_type);
-	while (cur < blocksize) {
-		struct page *page = bio_iter_page(&bbio->bio, iter);
-		const u32 pg_off = bio_iter_offset(&bbio->bio, iter);
-		const u32 cur_len = min(bio_iter_len(&bbio->bio, iter), blocksize - cur);
-		void *kaddr;
-
-		kaddr = kmap_local_page(page) + pg_off;
-		btrfs_csum_update(&cctx, kaddr, cur_len);
-		kunmap_local(kaddr);
-
-		bio_advance_iter_single(&bbio->bio, &iter, cur_len);
-		cur += cur_len;
-	}
-	btrfs_csum_final(&cctx, csum);
-
+	btrfs_csum_one_bio_block(fs_info, &bbio->bio, orig_iter, csum);
 	if (unlikely(memcmp(csum, csum_expected, fs_info->csum_size) != 0))
 		goto zeroit;
 	return true;
@@ -3601,8 +3611,6 @@ bool btrfs_bio_data_csum_ok(struct btrfs_bio *bbio,
 				    bbio->mirror_num);
 	if (dev)
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS);
-	cur = 0;
-	iter = *orig_iter;
 	while (cur < blocksize) {
 		struct page *page = bio_iter_page(&bbio->bio, iter);
 		const u32 pg_off = bio_iter_offset(&bbio->bio, iter);
-- 
2.54.0