2011-05-05 02:04:24

by Shaohua Li

Subject: [patch v3 1/3] block: add a non-queueable flush flag

flush request isn't queueable in some drives. Add a flag to let driver
notify block layer about this. We can optimize flush performance with the
knowledge.

Signed-off-by: Shaohua Li <[email protected]>
---
block/blk-settings.c | 6 ++++++
include/linux/blkdev.h | 7 +++++++
2 files changed, 13 insertions(+)

Index: linux/include/linux/blkdev.h
===================================================================
--- linux.orig/include/linux/blkdev.h 2011-05-04 14:23:42.000000000 +0800
+++ linux/include/linux/blkdev.h 2011-05-05 09:05:18.000000000 +0800
@@ -364,6 +364,7 @@ struct request_queue
* for flush operations
*/
unsigned int flush_flags;
+ unsigned int flush_not_queueable:1;
unsigned int flush_pending_idx:1;
unsigned int flush_running_idx:1;
unsigned long flush_pending_since;
@@ -843,6 +844,7 @@ extern void blk_queue_softirq_done(struc
extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern void blk_queue_flush(struct request_queue *q, unsigned int flush);
+extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);

extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
@@ -1111,6 +1113,11 @@ static inline unsigned int block_size(st
return bdev->bd_block_size;
}

+static inline bool queue_flush_queueable(struct request_queue *q)
+{
+ return !q->flush_not_queueable;
+}
+
typedef struct {struct page *v;} Sector;

unsigned char *read_dev_sector(struct block_device *, sector_t, Sector *);
Index: linux/block/blk-settings.c
===================================================================
--- linux.orig/block/blk-settings.c 2011-05-05 08:37:05.000000000 +0800
+++ linux/block/blk-settings.c 2011-05-05 09:02:16.000000000 +0800
@@ -790,6 +790,12 @@ void blk_queue_flush(struct request_queu
}
EXPORT_SYMBOL_GPL(blk_queue_flush);

+void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
+{
+ q->flush_not_queueable = !queueable;
+}
+EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
+
static int __init blk_settings_init(void)
{
blk_max_low_pfn = max_low_pfn - 1;

2011-05-05 02:17:45

by Jeff Garzik

Subject: Re: [patch v3 1/3] block: add a non-queueable flush flag

On 05/04/2011 09:59 PM, [email protected] wrote:
> flush request isn't queueable in some drives. Add a flag to let driver
> notify block layer about this. We can optimize flush performance with the
> knowledge.
>
> Signed-off-by: Shaohua Li<[email protected]>
> ---
> block/blk-settings.c | 6 ++++++
> include/linux/blkdev.h | 7 +++++++
> 2 files changed, 13 insertions(+)

hmmm.

This assumes that flush on new hardware, by default, is queueable.

I think the sense should be reversed: don't enable the optimization,
unless we know the optimization works.

That seems safer than always enabling the optimization, unless we know
it does not work. That is not a fail-safe mode of operation.

Jeff

2011-05-05 02:21:19

by Shaohua Li

Subject: Re: [patch v3 1/3] block: add a non-queueable flush flag

On Thu, May 05, 2011 at 10:17:39AM +0800, Jeff Garzik wrote:
> On 05/04/2011 09:59 PM, [email protected] wrote:
> > flush request isn't queueable in some drives. Add a flag to let driver
> > notify block layer about this. We can optimize flush performance with the
> > knowledge.
> >
> > Signed-off-by: Shaohua Li<[email protected]>
> > ---
> > block/blk-settings.c | 6 ++++++
> > include/linux/blkdev.h | 7 +++++++
> > 2 files changed, 13 insertions(+)
>
> hmmm.
>
> This assumes that flush on new hardware, by default, is queueable.
>
> I think the sense should be reversed: don't enable the optimization,
> unless we know the optimization works.
>
> That seems safer than always enabling the optimization, unless we know
> it does not work. That is not a fail-safe mode of operation.
This assumes flush is queueable by default. but I only enable the optimization
for non-queueable flush. So the optimization is off by default, please see
the second patch.

Thanks,
Shaohua

2011-05-05 07:54:06

by Tejun Heo

Subject: Re: [patch v3 1/3] block: add a non-queueable flush flag

On Thu, May 05, 2011 at 09:59:33AM +0800, [email protected] wrote:
> flush request isn't queueable in some drives. Add a flag to let driver
> notify block layer about this. We can optimize flush performance with the
> knowledge.
>
> Signed-off-by: Shaohua Li <[email protected]>

Acked-by: Tejun Heo <[email protected]>

Thanks.

--
tejun