block: add a BUILD_BUG_ON() for adding more bio flags than we have space

We have BIO_FLAG_LAST in the enum for bio specific flags, but it's
not used to check that we're not exceeding the size of them. Add
such a check.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index ab59a49..d7fbc7a 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1792,6 +1792,8 @@ static int __init init_bio(void)
 {
        int i;
 
+       BUILD_BUG_ON(BIO_FLAG_LAST > 8 * sizeof_field(struct bio, bi_flags));
+
        bio_integrity_init();
 
        for (i = 0; i < ARRAY_SIZE(bvec_slabs); i++) {