[PATCH 2/8] btrfs: introduce a pure data checksum checking helper

Christoph Hellwig
2022-05-22T11:48:11Z

From: Qu Wenruo <wqu@suse.com>

Although we have several data csum verification code, we never have a
function really just to verify checksum for one sector.

Function check_data_csum() do extra work for error reporting, thus it
requires a lot of extra things like file offset, bio_offset etc.

Function btrfs_verify_data_csum() is even worse, it will utizlie page
checked flag, which means it can not be utilized for direct IO pages.

Here we introduce a new helper, btrfs_check_sector_csum(), which really
only accept a sector in page, and expected checksum pointer.

We use this function to implement check_data_csum(), and export it for
incoming patch.

Signed-off-by: Qu Wenruo <wqu@suse.com>
[hch: keep passing the csum array as an arguments, as the callers want
to print it, rename per request]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/compression.c | 13 ++++---------
fs/btrfs/ctree.h | 2 ++
fs/btrfs/inode.c | 38 ++++++++++++++++++++++++++++----------
3 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index f4564f32f6d93..6ab82e142f1f8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -147,12 +147,10 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
u64 disk_start)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
- SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
const u32 csum_size = fs_info->csum_size;
const u32 sectorsize = fs_info->sectorsize;
struct page *page;
unsigned int i;
- char *kaddr;
u8 csum[BTRFS_CSUM_SIZE];
struct compressed_bio *cb = bio->bi_private;
u8 *cb_sum = cb->sums;
@@ -161,8 +159,6 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
test_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state))
return 0;

- shash->tfm = fs_info->csum_shash;
-
for (i = 0; i < cb->nr_pages; i++) {
u32 pg_offset;
u32 bytes_left = PAGE_SIZE;
@@ -175,12 +171,11 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
/* Hash through the page sector by sector */
for (pg_offset = 0; pg_offset < bytes_left;
pg_offset += sectorsize) {
- kaddr = kmap_atomic(page);
- crypto_shash_digest(shash, kaddr + pg_offset,
- sectorsize, csum);
- kunmap_atomic(kaddr);
+ int ret;

- if (memcmp(&csum, cb_sum, csum_size) != 0) {
+ ret = btrfs_check_sector_csum(fs_info, page, pg_offset,
+ csum, cb_sum);
+ if (ret) {
btrfs_print_data_csum_error(inode, disk_start,
csum, cb_sum, cb->mirror_num);
if (btrfs_bio(bio)->device)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0e49b1a0c0716..8dd7d36b83ecb 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3253,6 +3253,8 @@ u64 btrfs_file_extent_end(const struct btrfs_path *path);
/* inode.c */
void btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
int mirror_num, enum btrfs_compression_type compress_type);
+int btrfs_check_sector_csum(struct btrfs_fs_info *fs_info, struct page *page,
+ u32 pgoff, u8 *csum, u8 *csum_expected);
unsigned int btrfs_verify_data_csum(struct btrfs_bio *bbio,
u32 bio_offset, struct page *page,
u64 start, u64 end);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index da13bd0d10f12..e4acdec9ffc69 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3326,6 +3326,29 @@ void btrfs_writepage_endio_finish_ordered(struct btrfs_inode *inode,
finish_ordered_fn, uptodate);
}

+/*
+ * Verify the checksum for a single sector without any extra action that
+ * depend on the type of I/O.
+ */
+int btrfs_check_sector_csum(struct btrfs_fs_info *fs_info, struct page *page,
+ u32 pgoff, u8 *csum, u8 *csum_expected)
+{
+ SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+ char *kaddr;
+
+ ASSERT(pgoff + fs_info->sectorsize <= PAGE_SIZE);
+
+ shash->tfm = fs_info->csum_shash;
+
+ kaddr = kmap_local_page(page) + pgoff;
+ crypto_shash_digest(shash, kaddr, fs_info->sectorsize, csum);
+ kunmap_local(kaddr);
+
+ if (memcmp(csum, csum_expected, fs_info->csum_size))
+ return -EIO;
+ return 0;
+}
+
/*
* check_data_csum - verify checksum of one sector of uncompressed data
* @inode: inode
@@ -3336,14 +3359,15 @@ void btrfs_writepage_endio_finish_ordered(struct btrfs_inode *inode,
* @start: logical offset in the file
*
* The length of such check is always one sector size.
+ *
+ * When csum mismatch detected, we will also report the error and fill the
+ * corrupted range with zero. (thus it needs the extra parameters)
*/
static int check_data_csum(struct inode *inode, struct btrfs_bio *bbio,
u32 bio_offset, struct page *page, u32 pgoff,
u64 start)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
- SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
- char *kaddr;
u32 len = fs_info->sectorsize;
const u32 csum_size = fs_info->csum_size;
unsigned int offset_sectors;
@@ -3355,16 +3379,10 @@ static int check_data_csum(struct inode *inode, struct btrfs_bio *bbio,
offset_sectors = bio_offset >> fs_info->sectorsize_bits;
csum_expected = ((u8 *)bbio->csum) + offset_sectors * csum_size;

- kaddr = kmap_atomic(page);
- shash->tfm = fs_info->csum_shash;
-
- crypto_shash_digest(shash, kaddr + pgoff, len, csum);
- kunmap_atomic(kaddr);
-
- if (memcmp(csum, csum_expected, csum_size))
+ if (btrfs_check_sector_csum(fs_info, page, pgoff, csum, csum_expected))
goto zeroit;
-
return 0;
+
zeroit:
btrfs_print_data_csum_error(BTRFS_I(inode), start, csum, csum_expected,
bbio->mirror_num);
--
2.30.2