On Fri, Jun 18, 2010 at 09:47:04AM +0200, Christoph Hellwig wrote:
> Remove the current bio flags and reuse the request flags for the bio, too.
> This allows to more easily trace the type of I/O from the filesystem
> down to the block driver. There were two flags in the bio that were
> missing in the requests: BIO_RW_UNPLUG and BIO_RW_AHEAD. Also I've
> renamed two request flags that had a superflous RW in them.
>
> Note that the flags are in bio.h despite having the REQ_ name - as
> blkdev.h includes bio.h that is the only way to go for now.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
>
> Index: linux-2.6/block/blk-core.c
> ===================================================================
> --- linux-2.6.orig/block/blk-core.c 2010-06-17 13:21:18.000000000 +0200
> +++ linux-2.6/block/blk-core.c 2010-06-17 13:26:55.958005535 +0200
> @@ -1139,27 +1139,9 @@ void init_request_from_bio(struct reques
> {
> req->cpu = bio->bi_comp_cpu;
> req->cmd_type = REQ_TYPE_FS;
> -
> - /*
> - * Inherit FAILFAST from bio (for read-ahead, and explicit
> - * FAILFAST). FAILFAST flags are identical for req and bio.
> - */
> - if (bio_rw_flagged(bio, BIO_RW_AHEAD))
> + req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
> + if (bio->bi_rw & REQ_RAHEAD)
> req->cmd_flags |= REQ_FAILFAST_MASK;
> - else
> - req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
> -
> - if (bio_rw_flagged(bio, BIO_RW_DISCARD))
> - req->cmd_flags |= REQ_DISCARD;
> - if (bio_rw_flagged(bio, BIO_RW_BARRIER))
> - req->cmd_flags |= REQ_HARDBARRIER;
> - if (bio_rw_flagged(bio, BIO_RW_SYNCIO))
> - req->cmd_flags |= REQ_RW_SYNC;
> - if (bio_rw_flagged(bio, BIO_RW_META))
> - req->cmd_flags |= REQ_RW_META;
> - if (bio_rw_flagged(bio, BIO_RW_NOIDLE))
> - req->cmd_flags |= REQ_NOIDLE;
Much better for branches and icache.
Any reason not to make REQ_RAHEAD include REQ_FAILFAST_MASK?
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