From: Dave Hansen <dave.hansen@intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
linux-ide <linux-ide@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Cc: lsf-pc@lists.linux-foundation.org
Subject: Re: [LSF/MM TOPIC] Fixing large block devices on 32 bit
Date: Fri, 31 Jan 2014 13:47:18 -0800 [thread overview]
Message-ID: <52EC19E6.9010509@intel.com> (raw)
In-Reply-To: <1391194978.2172.20.camel@dabdike.int.hansenpartnership.com>
On 01/31/2014 11:02 AM, James Bottomley wrote:
> 3. Increase pgoff_t and the radix tree indexes to u64 for
> CONFIG_LBDAF. This will blow out the size of struct page on 32
> bits by 4 bytes and may have other knock on effects, but at
> least it will be transparent.
I'm not sure how many acrobatics we want to go through for 32-bit, but...
Between page->mapping and page->index, we have 64 bits of space, which
*should* be plenty to uniquely identify a block. We could easily add a
second-level lookup somewhere so that we store some cookie for the
address_space instead of a direct pointer. How many devices would need,
practically? 8 bits worth?
WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave.hansen@intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
linux-ide <linux-ide@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Cc: lsf-pc@lists.linux-foundation.org
Subject: Re: [LSF/MM TOPIC] Fixing large block devices on 32 bit
Date: Fri, 31 Jan 2014 13:47:18 -0800 [thread overview]
Message-ID: <52EC19E6.9010509@intel.com> (raw)
In-Reply-To: <1391194978.2172.20.camel@dabdike.int.hansenpartnership.com>
On 01/31/2014 11:02 AM, James Bottomley wrote:
> 3. Increase pgoff_t and the radix tree indexes to u64 for
> CONFIG_LBDAF. This will blow out the size of struct page on 32
> bits by 4 bytes and may have other knock on effects, but at
> least it will be transparent.
I'm not sure how many acrobatics we want to go through for 32-bit, but...
Between page->mapping and page->index, we have 64 bits of space, which
*should* be plenty to uniquely identify a block. We could easily add a
second-level lookup somewhere so that we store some cookie for the
address_space instead of a direct pointer. How many devices would need,
practically? 8 bits worth?
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next prev parent reply other threads:[~2014-01-31 21:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-31 19:02 [LSF/MM TOPIC] Fixing large block devices on 32 bit James Bottomley
2014-01-31 19:26 ` Dave Jones
2014-01-31 23:16 ` James Bottomley
2014-01-31 21:20 ` Chris Mason
2014-01-31 21:20 ` Chris Mason
2014-01-31 23:14 ` James Bottomley
2014-01-31 21:47 ` Dave Hansen [this message]
2014-01-31 21:47 ` Dave Hansen
2014-01-31 23:27 ` James Bottomley
2014-01-31 23:27 ` James Bottomley
2014-02-01 0:19 ` Dave Hansen
2014-02-01 0:25 ` Kirill A. Shutemov
2014-02-01 0:32 ` Dave Hansen
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