From: Dan Williams <dan.j.williams@intel.com>
To: Jens Axboe <axboe@fb.com>
Cc: linux-block@vger.kernel.org,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Dave Chinner <david@fromorbit.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
Jan Kara <jack@suse.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Matthew Wilcox <willy@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH 2/2] block: use DAX for partition table reads
Date: Fri, 29 Jan 2016 09:54:28 -0800 [thread overview]
Message-ID: <CAPcyv4hL-QU1MxmQ-4wiLen2wRFD2=4R8nsoGxjVu-tbLgqobA@mail.gmail.com> (raw)
In-Reply-To: <56ABA561.9070606@fb.com>
On Fri, Jan 29, 2016 at 9:46 AM, Jens Axboe <axboe@fb.com> wrote:
> On 01/29/2016 08:18 AM, Dan Williams wrote:
>>
>> +unsigned char *read_dev_sector(struct block_device *bdev, sector_t n,
>> Sector *p)
>> +{
>> struct page *page;
>>
>> - page = read_mapping_page(mapping, (pgoff_t)(n >>
>> (PAGE_CACHE_SHIFT-9)),
>> - NULL);
>> + /* don't populate page cache for dax capable devices */
>> + if (IS_DAX(bdev->bd_inode))
>> + page = read_dax_sector(bdev, n);
>> + else
>> + page = read_pagecache_sector(bdev, n);
>> +
>
>
> Fall back to non-dax, if dax fails?
I think we need to fail hard otherwise we're back to the original
problem of confusing the dax code that expects to find an empty page
cache.
>
>> +struct page *read_dax_sector(struct block_device *bdev, sector_t n)
>> +{
>> + struct page *page = __page_cache_alloc(GFP_KERNEL | __GFP_COLD);
>
>
> Why isn't that just alloc_pages()?
Just for symmetry with the same allocation that the pagecache path
makes, but alloc_pages() works too...
WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: Jens Axboe <axboe@fb.com>
Cc: linux-block@vger.kernel.org,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
Dave Chinner <david@fromorbit.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
Jan Kara <jack@suse.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Matthew Wilcox <willy@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH 2/2] block: use DAX for partition table reads
Date: Fri, 29 Jan 2016 09:54:28 -0800 [thread overview]
Message-ID: <CAPcyv4hL-QU1MxmQ-4wiLen2wRFD2=4R8nsoGxjVu-tbLgqobA@mail.gmail.com> (raw)
In-Reply-To: <56ABA561.9070606@fb.com>
On Fri, Jan 29, 2016 at 9:46 AM, Jens Axboe <axboe@fb.com> wrote:
> On 01/29/2016 08:18 AM, Dan Williams wrote:
>>
>> +unsigned char *read_dev_sector(struct block_device *bdev, sector_t n,
>> Sector *p)
>> +{
>> struct page *page;
>>
>> - page = read_mapping_page(mapping, (pgoff_t)(n >>
>> (PAGE_CACHE_SHIFT-9)),
>> - NULL);
>> + /* don't populate page cache for dax capable devices */
>> + if (IS_DAX(bdev->bd_inode))
>> + page = read_dax_sector(bdev, n);
>> + else
>> + page = read_pagecache_sector(bdev, n);
>> +
>
>
> Fall back to non-dax, if dax fails?
I think we need to fail hard otherwise we're back to the original
problem of confusing the dax code that expects to find an empty page
cache.
>
>> +struct page *read_dax_sector(struct block_device *bdev, sector_t n)
>> +{
>> + struct page *page = __page_cache_alloc(GFP_KERNEL | __GFP_COLD);
>
>
> Why isn't that just alloc_pages()?
Just for symmetry with the same allocation that the pagecache path
makes, but alloc_pages() works too...
next prev parent reply other threads:[~2016-01-29 17:54 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 15:18 [PATCH 0/2] block: fix raw block device dax support Dan Williams
2016-01-29 15:18 ` Dan Williams
2016-01-29 15:18 ` [PATCH 1/2] block: revert runtime dax control of the raw block device Dan Williams
2016-01-29 15:18 ` Dan Williams
2016-01-29 17:54 ` Ross Zwisler
2016-01-29 17:54 ` Ross Zwisler
2016-01-29 15:18 ` [PATCH 2/2] block: use DAX for partition table reads Dan Williams
2016-01-29 15:18 ` Dan Williams
2016-01-29 17:46 ` Jens Axboe
2016-01-29 17:46 ` Jens Axboe
2016-01-29 17:46 ` Jens Axboe
2016-01-29 17:54 ` Dan Williams [this message]
2016-01-29 17:54 ` Dan Williams
2016-01-29 19:24 ` Ross Zwisler
2016-01-29 19:24 ` Ross Zwisler
2016-01-29 22:45 ` Matthew Wilcox
2016-01-29 22:45 ` Matthew Wilcox
2016-01-30 0:33 ` [PATCH v2] " Dan Williams
2016-01-30 0:33 ` Dan Williams
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