[PATCH AUTOSEL 5.17 14/21] btrfs: handle csum lookup errors properly on reads

Sasha Levin
2022-03-28T19:42:28Z

From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit 1784b7d502a94b561eae58249adde5f72c26eb3c ]

Currently any error we get while trying to lookup csums during reads
shows up as a missing csum, and then on the read completion side we
print an error saying there was a csum mismatch and we increase the
device corruption count.

However we could have gotten an EIO from the lookup. We could also be
inside of a memory constrained container and gotten a ENOMEM while
trying to do the read. In either case we don't want to make this look
like a file system corruption problem, we want to make it look like the
actual error it is. Capture any negative value, convert it to the
appropriate blk_status_t, free the csum array if we have one and bail.

Note: a possible improvement would be to make the relocation code look
up the owning inode and see if it's marked as NODATASUM and set
EXTENT_NODATASUM there, that way if there's corruption and there isn't a
checksum when we want it we can fail here rather than later.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/file-item.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index f9813853eaf8..70f5cbd9020b 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -368,6 +368,7 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ struct btrfs_bio *bbio = NULL;
struct btrfs_path *path;
const u32 sectorsize = fs_info->sectorsize;
const u32 csum_size = fs_info->csum_size;
@@ -377,6 +378,7 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst
u8 *csum;
const unsigned int nblocks = orig_len >> fs_info->sectorsize_bits;
int count = 0;
+ blk_status_t ret = BLK_STS_OK;

if ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) ||
test_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state))
@@ -400,7 +402,7 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst
return BLK_STS_RESOURCE;

if (!dst) {
- struct btrfs_bio *bbio = btrfs_bio(bio);
+ bbio = btrfs_bio(bio);

if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {
bbio->csum = kmalloc_array(nblocks, csum_size, GFP_NOFS);
@@ -456,21 +458,27 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst

count = search_csum_tree(fs_info, path, cur_disk_bytenr,
search_len, csum_dst);
- if (count <= 0) {
- /*
- * Either we hit a critical error or we didn't find
- * the csum.
- * Either way, we put zero into the csums dst, and skip
- * to the next sector.
- */
+ if (count < 0) {
+ ret = errno_to_blk_status(count);
+ if (bbio)
+ btrfs_bio_free_csum(bbio);
+ break;
+ }
+
+ /*
+ * We didn't find a csum for this range. We need to make sure
+ * we complain loudly about this, because we are not NODATASUM.
+ *
+ * However for the DATA_RELOC inode we could potentially be
+ * relocating data extents for a NODATASUM inode, so the inode
+ * itself won't be marked with NODATASUM, but the extent we're
+ * copying is in fact NODATASUM. If we don't find a csum we
+ * assume this is the case.
+ */
+ if (count == 0) {
memset(csum_dst, 0, csum_size);
count = 1;

- /*
- * For data reloc inode, we need to mark the range
- * NODATASUM so that balance won't report false csum
- * error.
- */
if (BTRFS_I(inode)->root->root_key.objectid ==
BTRFS_DATA_RELOC_TREE_OBJECTID) {
u64 file_offset;
@@ -491,7 +499,7 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst
}

btrfs_free_path(path);
- return BLK_STS_OK;
+ return ret;
}

int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
--
2.34.1