David Woodhouse <dwmw2@xxxxxxxxxxxxx> writes:
> Some block devices benefit from a hint that they can forget the contents
> of certain sectors. Add basic support for this to the block core, along
> with a 'blkdev_issue_discard()' helper function which issues such
> requests.
>
> Although blkdev_issue_discard() can take an end_io function, it's
> acceptable to leave that as NULL and in that case the allocated bio will
> be automatically freed. Most of the time, it's expected that callers
> won't care about when, or even _if_, the request completes. It's only a
> hint to the device anyway. By definition, the file system doesn't _care_
> about these sectors any more.
Looks like good start. Thanks. Although I'm not quite sure it helps, is
there any plan to merge bios?
> +int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> + unsigned nr_sects, bio_end_io_t end_io)
> +{
> + struct request_queue *q;
[...]
> +
> + bio->bi_end_io = end_io;
> + bio->bi_bdev = bdev;
> + bio->bi_sector = sector;
> + bio->bi_size = nr_sects << 9;
> + submit_bio(1 << BIO_RW_DISCARD, bio);
> + return 0;
> +}
If fs merges contiguous blocks to one bio, bi_size will overflow.
Will we have to limit (of the device?) and separate for the device?
Or how about to have #define for discard bio for BIO_RW_DISCARD users?
> @@ -185,10 +188,16 @@ struct bio {
> #define bio_failfast(bio) ((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
> #define bio_rw_ahead(bio) ((bio)->bi_rw & (1 << BIO_RW_AHEAD))
> #define bio_rw_meta(bio) ((bio)->bi_rw & (1 << BIO_RW_META))
> +#define bio_discard(bio) ((bio)->bi_rw & (1 << BIO_RW_DISCARD))
> #define bio_empty_barrier(bio) (bio_barrier(bio) && !(bio)->bi_size)
>
> +#define bio_dataless(bio) (!(bio)->bi_io_vec)
The following seems good to convert to bio_dataless?
Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
---
mm/bounce.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/bounce.c~test mm/bounce.c
--- linux-2.6/mm/bounce.c~test 2008-08-07 00:04:26.000000000 +0900
+++ linux-2.6-hirofumi/mm/bounce.c 2008-08-07 00:04:57.000000000 +0900
@@ -267,7 +267,7 @@ void blk_queue_bounce(struct request_que
/*
* Data-less bio, nothing to bounce
*/
- if (bio_empty_barrier(*bio_orig))
+ if (bio_dataless(*bio_orig)) {
return;
/*
_
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
