dm verity fec: fix misaligned RS roots IO

commit df7b59ba9245 ("dm verity: fix FEC for RS roots unaligned to
block size") introduced the possibility for misaligned roots IO
relative to the underlying device's logical block size. E.g. Android's
default RS roots=2 results in dm_bufio->block_size=1024, which causes
the following EIO if the logical block size of the device is 4096,
given v->data_dev_block_bits=12:

E sd 0    : 0:0:0: [sda] tag#30 request not aligned to the logical block size
E blk_update_request: I/O error, dev sda, sector 10368424 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
E device-mapper: verity-fec: 254:8: FEC 9244672: parity read failed (block 18056): -5

Fix this by onlu using f->roots for dm_bufio blocksize IFF it is
aligned to v->data_dev_block_bits.

Fixes: df7b59ba9245 ("dm verity: fix FEC for RS roots unaligned to block size")
Cc: stable@vger.kernel.org
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 66f4c63..cea2b37 100644 (file)
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -65,7 +65,7 @@ static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
        u8 *res;
 
        position = (index + rsb) * v->fec->roots;
-       block = div64_u64_rem(position, v->fec->roots << SECTOR_SHIFT, &rem);
+       block = div64_u64_rem(position, v->fec->io_size, &rem);
        *offset = (unsigned)rem;
 
        res = dm_bufio_read(v->fec->bufio, block, buf);
@@ -154,7 +154,7 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
 
                /* read the next block when we run out of parity bytes */
                offset += v->fec->roots;
-               if (offset >= v->fec->roots << SECTOR_SHIFT) {
+               if (offset >= v->fec->io_size) {
                        dm_bufio_release(buf);
 
                        par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
@@ -742,8 +742,13 @@ int verity_fec_ctr(struct dm_verity *v)
                return -E2BIG;
        }
 
+       if ((f->roots << SECTOR_SHIFT) & ((1 << v->data_dev_block_bits) - 1))
+               f->io_size = 1 << v->data_dev_block_bits;
+       else
+               f->io_size = v->fec->roots << SECTOR_SHIFT;
+
        f->bufio = dm_bufio_client_create(f->dev->bdev,
-                                         f->roots << SECTOR_SHIFT,
+                                         f->io_size,
                                          1, 0, NULL, NULL);
        if (IS_ERR(f->bufio)) {
                ti->error = "Cannot initialize FEC bufio client";

diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
index 42fbd3a..3c46c8d 100644 (file)
--- a/drivers/md/dm-verity-fec.h
+++ b/drivers/md/dm-verity-fec.h
@@ -36,6 +36,7 @@ struct dm_verity_fec {
        struct dm_dev *dev;     /* parity data device */
        struct dm_bufio_client *data_bufio;     /* for data dev access */
        struct dm_bufio_client *bufio;          /* for parity data access */
+       size_t io_size;         /* IO size for roots */
        sector_t start;         /* parity data start in blocks */
        sector_t blocks;        /* number of blocks covered */
        sector_t rounds;        /* number of interleaving rounds */