From: Paolo Bonzini <pbonzini@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk,
snitzer@redhat.com, martin.petersen@oracle.com,
david@fromorbit.com, xfs@oss.sgi.com, dm-devel@redhat.com,
hch@lst.de
Subject: Re: [dm-devel] [PATCH v2 2/3] block: reorganize rounding of max_discard_sectors
Date: Tue, 03 Jul 2012 13:47:31 +0200 [thread overview]
Message-ID: <4FF2DBD3.4080800@redhat.com> (raw)
In-Reply-To: <20120703024910.GC3586@redhat.com>
Il 03/07/2012 04:49, Vivek Goyal ha scritto:
>> > + /* Zero-sector (unknown) and one-sector granularities are the same. */
>> > + granularity = max(q->limits.discard_granularity >> 9, 1U);
>> > +
>> > /*
>> > * Ensure that max_discard_sectors is of the proper
>> > * granularity
>> > */
>> > max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
>> > + max_discard_sectors = round_down(max_discard_sectors, granularity);
>> > if (unlikely(!max_discard_sectors)) {
>> > /* Avoid infinite loop below. Being cautious never hurts. */
>> > return -EOPNOTSUPP;
>> > - } else if (q->limits.discard_granularity) {
>> > - unsigned int disc_sects = q->limits.discard_granularity >> 9;
>> > -
>> > - max_discard_sectors &= ~(disc_sects - 1);
> This is kind of odd. If discard_granularity is zero, we assume that
> discards are supported and granularity is 1. But if max_discard_sectors
> is zero, we assume discards are disabled. Not sure if we should treat
> max_discard_sectors and discard_granularity in same way or not.
Yes, this keeps the same behavior as before. It is also the one that is
consistent with drivers/scsi/sd.c. sd_config_discard always sets
limits.discard_granularity and then uses limits.max_discard_sectors to
disable discards.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: axboe@kernel.dk, martin.petersen@oracle.com, snitzer@redhat.com,
linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
dm-devel@redhat.com, hch@lst.de
Subject: Re: [dm-devel] [PATCH v2 2/3] block: reorganize rounding of max_discard_sectors
Date: Tue, 03 Jul 2012 13:47:31 +0200 [thread overview]
Message-ID: <4FF2DBD3.4080800@redhat.com> (raw)
In-Reply-To: <20120703024910.GC3586@redhat.com>
Il 03/07/2012 04:49, Vivek Goyal ha scritto:
>> > + /* Zero-sector (unknown) and one-sector granularities are the same. */
>> > + granularity = max(q->limits.discard_granularity >> 9, 1U);
>> > +
>> > /*
>> > * Ensure that max_discard_sectors is of the proper
>> > * granularity
>> > */
>> > max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
>> > + max_discard_sectors = round_down(max_discard_sectors, granularity);
>> > if (unlikely(!max_discard_sectors)) {
>> > /* Avoid infinite loop below. Being cautious never hurts. */
>> > return -EOPNOTSUPP;
>> > - } else if (q->limits.discard_granularity) {
>> > - unsigned int disc_sects = q->limits.discard_granularity >> 9;
>> > -
>> > - max_discard_sectors &= ~(disc_sects - 1);
> This is kind of odd. If discard_granularity is zero, we assume that
> discards are supported and granularity is 1. But if max_discard_sectors
> is zero, we assume discards are disabled. Not sure if we should treat
> max_discard_sectors and discard_granularity in same way or not.
Yes, this keeps the same behavior as before. It is also the one that is
consistent with drivers/scsi/sd.c. sd_config_discard always sets
limits.discard_granularity and then uses limits.max_discard_sectors to
disable discards.
Paolo
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next prev parent reply other threads:[~2012-07-03 11:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-02 13:20 [PATCH v2 0/3] block: improvements for discard alignment Paolo Bonzini
2012-07-02 13:20 ` Paolo Bonzini
2012-07-02 13:20 ` [PATCH v2 1/3] block: add sysfs entry for discard_alignment Paolo Bonzini
2012-07-02 13:20 ` Paolo Bonzini
2012-07-03 2:34 ` [dm-devel] " Vivek Goyal
2012-07-03 2:34 ` Vivek Goyal
2012-07-03 3:59 ` Mike Snitzer
2012-07-03 3:59 ` Mike Snitzer
2012-07-03 11:51 ` [dm-devel] " Paolo Bonzini
2012-07-03 11:51 ` Paolo Bonzini
2012-07-03 14:00 ` Vivek Goyal
2012-07-03 14:00 ` Vivek Goyal
2012-07-03 14:21 ` Paolo Bonzini
2012-07-03 14:21 ` Paolo Bonzini
2012-07-03 14:39 ` Vivek Goyal
2012-07-03 14:39 ` Vivek Goyal
2012-07-03 14:40 ` Paolo Bonzini
2012-07-03 14:40 ` Paolo Bonzini
2012-07-03 14:45 ` Vivek Goyal
2012-07-03 14:45 ` Vivek Goyal
2012-07-02 13:20 ` [PATCH v2 2/3] block: reorganize rounding of max_discard_sectors Paolo Bonzini
2012-07-02 13:20 ` Paolo Bonzini
2012-07-03 2:49 ` [dm-devel] " Vivek Goyal
2012-07-03 2:49 ` Vivek Goyal
2012-07-03 11:47 ` Paolo Bonzini [this message]
2012-07-03 11:47 ` Paolo Bonzini
2012-07-02 13:20 ` [PATCH v2 3/3] block: split discard into aligned requests Paolo Bonzini
2012-07-02 13:20 ` Paolo Bonzini
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