block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

With the introduction of BIO_NO_PAGE_REF we've used up all available bits
in bio::bi_flags.

Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
causing crashes.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 8d516d508ae357399bb555600477ae9356548ea2..c2592c5d70b98751a4b6e26c40938afc33a4869b 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -2218,6 +2218,9 @@ static int __init init_bio(void)
        bio_slab_nr = 0;
        bio_slabs = kcalloc(bio_slab_max, sizeof(struct bio_slab),
                            GFP_KERNEL);
+
+       BUILD_BUG_ON(BIO_FLAG_LAST > BVEC_POOL_OFFSET);
+
        if (!bio_slabs)
                panic("bio: can't allocate bios\n");
 

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 791fee35df8886d11580d4c54f4b55dae64de3db..be418275763c54750cc29b103d8b04a2645940a2 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -215,21 +215,24 @@ struct bio {
 /*
  * bio flags
  */
-#define BIO_NO_PAGE_REF        0       /* don't put release vec pages */
-#define BIO_SEG_VALID  1       /* bi_phys_segments valid */
-#define BIO_CLONED     2       /* doesn't own data */
-#define BIO_BOUNCED    3       /* bio is a bounce bio */
-#define BIO_USER_MAPPED 4      /* contains user pages */
-#define BIO_NULL_MAPPED 5      /* contains invalid user pages */
-#define BIO_QUIET      6       /* Make BIO Quiet */
-#define BIO_CHAIN      7       /* chained bio, ->bi_remaining in effect */
-#define BIO_REFFED     8       /* bio has elevated ->bi_cnt */
-#define BIO_THROTTLED  9       /* This bio has already been subjected to
+enum {
+       BIO_NO_PAGE_REF,        /* don't put release vec pages */
+       BIO_SEG_VALID,          /* bi_phys_segments valid */
+       BIO_CLONED,             /* doesn't own data */
+       BIO_BOUNCED,            /* bio is a bounce bio */
+       BIO_USER_MAPPED,        /* contains user pages */
+       BIO_NULL_MAPPED,        /* contains invalid user pages */
+       BIO_QUIET,              /* Make BIO Quiet */
+       BIO_CHAIN,              /* chained bio, ->bi_remaining in effect */
+       BIO_REFFED,             /* bio has elevated ->bi_cnt */
+       BIO_THROTTLED,          /* This bio has already been subjected to
                                 * throttling rules. Don't do it again. */
-#define BIO_TRACE_COMPLETION 10        /* bio_endio() should trace the final completion
+       BIO_TRACE_COMPLETION,   /* bio_endio() should trace the final completion
                                 * of this bio. */
-#define BIO_QUEUE_ENTERED 11   /* can use blk_queue_enter_live() */
-#define BIO_TRACKED 12         /* set if bio goes through the rq_qos path */
+       BIO_QUEUE_ENTERED,      /* can use blk_queue_enter_live() */
+       BIO_TRACKED,            /* set if bio goes through the rq_qos path */
+       BIO_FLAG_LAST
+};
 
 /* See BVEC_POOL_OFFSET below before adding new flags */