At most 25 entries in dm_verity_fec_io::erasures are used: the maximum
number of FEC roots plus one.  Therefore, set the array size
accordingly.  This reduces the size of dm_verity_fec_io by 912 bytes.

Note: a later commit introduces a constant DM_VERITY_FEC_MAX_ROOTS,
which allows the size to be more clearly expressed as
DM_VERITY_FEC_MAX_ROOTS + 1.  This commit just fixes the size first.

Fixes: a739ff3f543a ("dm verity: add support for forward error correction")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 drivers/md/dm-verity-fec.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
index 35d28d9f8a9b0..32ca2bfee1db7 100644
--- a/drivers/md/dm-verity-fec.h
+++ b/drivers/md/dm-verity-fec.h
@@ -45,11 +45,12 @@ struct dm_verity_fec {
 };
 
 /* per-bio data */
 struct dm_verity_fec_io {
 	struct rs_control *rs;	/* Reed-Solomon state */
-	int erasures[DM_VERITY_FEC_MAX_RSN];	/* erasures for decode_rs8 */
+	/* erasures for decode_rs8 */
+	int erasures[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN + 1];
 	u8 *output;		/* buffer for corrected output */
 	unsigned int level;		/* recursion level */
 	unsigned int nbufs;		/* number of buffers allocated */
 	/*
 	 * Buffers for deinterleaving RS blocks.  Each buffer has space for
-- 
2.52.0