[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAPcyv4hL-QU1MxmQ-4wiLen2wRFD2=4R8nsoGxjVu-tbLgqobA@mail.gmail.com>
Date: Fri, 29 Jan 2016 09:54:28 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Jens Axboe <axboe@...com>
Cc: linux-block@...r.kernel.org,
"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
Dave Chinner <david@...morbit.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>,
Jan Kara <jack@...e.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Matthew Wilcox <willy@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 2/2] block: use DAX for partition table reads
On Fri, Jan 29, 2016 at 9:46 AM, Jens Axboe <axboe@...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...
Powered by blists - more mailing lists