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Re: [dm-devel] [PATCH v2 1/3] block: add sysfs entry for discard_alignme

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: Re: [dm-devel] [PATCH v2 1/3] block: add sysfs entry for discard_alignment
From: Vivek Goyal <vgoyal@xxxxxxxxxx>
Date: Tue, 3 Jul 2012 10:45:09 -0400
Cc: linux-kernel@xxxxxxxxxxxxxxx, axboe@xxxxxxxxx, snitzer@xxxxxxxxxx, martin.petersen@xxxxxxxxxx, david@xxxxxxxxxxxxx, xfs@xxxxxxxxxxx, dm-devel@xxxxxxxxxx, hch@xxxxxx
In-reply-to: <4FF30468.30407@xxxxxxxxxx>
References: <1341235225-27551-1-git-send-email-pbonzini@xxxxxxxxxx> <1341235225-27551-2-git-send-email-pbonzini@xxxxxxxxxx> <20120703023442.GB3586@xxxxxxxxxx> <4FF2DCB1.2090704@xxxxxxxxxx> <20120703140048.GC11272@xxxxxxxxxx> <4FF2FFEE.4000401@xxxxxxxxxx> <20120703143949.GE11272@xxxxxxxxxx> <4FF30468.30407@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Jul 03, 2012 at 04:40:40PM +0200, Paolo Bonzini wrote:
> Il 03/07/2012 16:39, Vivek Goyal ha scritto:
> >> > +static inline int bdev_discard_alignment(struct block_device *bdev)
> >> > +{
> >> > +        struct request_queue *q = bdev_get_queue(bdev);
> >> > +
> >> > +        if (bdev != bdev->bd_contains)
> >> > +                return bdev->bd_part->discard_alignment;
> >> > +
> >> > +        return q->limits.discard_alignment;
> >> > +}
> >> > +
> >> >  static inline unsigned int queue_discard_zeroes_data(struct 
> >> > request_queue *q)
> >> >  {
> >> >          if (q->limits.max_discard_sectors && 
> >> > q->limits.discard_zeroes_data == 1)
> >> > diff --git a/block/blk-lib.c b/block/blk-lib.c
> >> > index b2bde5c..77d8869 100644
> >> > --- a/block/blk-lib.c
> >> > +++ b/block/blk-lib.c
> >> > @@ -58,7 +58,7 @@ int blkdev_issue_discard(struct block_device *bdev, 
> >> > sector_t sector,
> >> >          /* Zero-sector (unknown) and one-sector granularities are the 
> >> > same.  */
> >> >          granularity = max(q->limits.discard_granularity >> 9, 1U);
> >> >          mask = granularity - 1;
> >> > -        alignment = (q->limits.discard_alignment >> 9) & mask;
> >> > +        alignment = bdev_discard_alignment(bdev) >> 9;
> > Why are you removing AND with mask operation? I don't see any AND
> > operation being done in bdev_discard_alignment().
> 
> For partitions it is done by queue_limits_discard_alignment.  For disks,
> it shouldn't be necessary at all but I can leave it.

Ok. I am fine with both with and without mask.

Thanks
Vivek

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