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block: add helpers to run flush_dcache_page() against a bio and a request's pages

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Mtdblock driver doesn't call flush_dcache_page for pages in request.  So,
this causes problems on architectures where the icache doesn't fill from
the dcache or with dcache aliases.  The patch fixes this.

The ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE symbol was introduced to avoid
pointless empty cache-thrashing loops on architectures for which
flush_dcache_page() is a no-op.  Every architecture was provided with this
flush pages on architectires where ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE is
equal 1 or do nothing otherwise.

See "fix mtd_blkdevs problem with caches on some architectures" discussion
on LKML for more information.

Signed-off-by: Ilya Loginov <isloginov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Peter Horton <phorton@bitbox.co.uk>
Cc: "Ed L. Cashin" <ecashin@coraid.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Ilya Loginov
2009-11-26 09:16:19 +01:00
committed by Jens Axboe
parent 3586e917f2
commit 2d4dc890b5
29 changed files with 83 additions and 0 deletions
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19
block/blk-core.c
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@@ -2358,6 +2358,25 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
rq->rq_disk = bio->bi_bdev->bd_disk;
}
#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
/**
* rq_flush_dcache_pages - Helper function to flush all pages in a request
* @rq: the request to be flushed
*
* Description:
* Flush all pages in @rq.
*/
void rq_flush_dcache_pages(struct request *rq)
{
struct req_iterator iter;
struct bio_vec *bvec;
rq_for_each_segment(bvec, rq, iter)
flush_dcache_page(bvec->bv_page);
}
EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
#endif
/**
* blk_lld_busy - Check if underlying low-level drivers of a device are busy
* @q : the queue of the device being checked