[PATCH 14/17] btrfs: make btrfs_readpage_end_io_hook() follow sector size

[Qu Wenruo <wqu@suse.com>]

Currently btrfs_readpage_end_io_hook() just pass the whole page to
check_data_csum(), which is fine since we only support sectorsize ==
PAGE_SIZE.

To support subpage RO support, we need to properly honor per-sector
checksum verification, just like what we did in dio read path.

This patch will do the csum verification in a for loop, starts with
pg_off == start - page_offset(page), with sectorsize increasement for
each loop.

For sectorsize == PAGE_SIZE case, the pg_off will always be 0, and we
will only finish with just one loop.

For subpage, we do the proper loop.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/inode.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 078735aa0f68..8bd14dda2067 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2851,9 +2851,12 @@ static int btrfs_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 				      u64 start, u64 end, int mirror)
 {
 	size_t offset = start - page_offset(page);
+	size_t pg_off;
 	struct inode *inode = page->mapping->host;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
+	u32 sectorsize = root->fs_info->sectorsize;
+	bool found_err = false;
 
 	if (PageChecked(page)) {
 		ClearPageChecked(page);
@@ -2870,7 +2873,17 @@ static int btrfs_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	}
 
 	phy_offset >>= inode->i_sb->s_blocksize_bits;
-	return check_data_csum(inode, io_bio, phy_offset, page, offset);
+	for (pg_off = offset; pg_off < end - page_offset(page);
+	     pg_off += sectorsize, phy_offset++) {
+		int ret;
+
+		ret = check_data_csum(inode, io_bio, phy_offset, page, pg_off);
+		if (ret < 0)
+			found_err = true;
+	}
+	if (found_err)
+		return -EIO;
+	return 0;
 }
 
 /*
-- 
2.28.0