brd: warn on un-aligned buffer

Queue dma alignment limit requires users(fs, target, ...) of block layer
to pass aligned buffer.

So far brd doesn't support un-aligned buffer, even though it is easy
to support it.

However, given brd is often used for debug purpose, and there are other
drivers which can't support un-aligned buffer too.

So add warning so that brd users know what to fix.

Reported-by: Stephen Rust <srust@blockbridge.com>
Cc: Stephen Rust <srust@blockbridge.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index c2e5b2a..a8730cc 100644 (file)
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -297,6 +297,10 @@ static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
                unsigned int len = bvec.bv_len;
                int err;
 
+               /* Don't support un-aligned buffer */
+               WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) ||
+                               (len & (SECTOR_SIZE - 1)));
+
                err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset,
                                  bio_op(bio), sector);
                if (err)