Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin() called

From	Waiman Long <waiman.long@hpe.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin() called
Date	2016-04-26 18:40 +0200
Message-ID	<rsebM-2ma-11@gated-at.bofh.it> (permalink)
References	<rnb4R-3n3-11@gated-at.bofh.it> <rnb4R-3n3-9@gated-at.bofh.it> <rq7o7-5F5-27@gated-at.bofh.it> <rqrmO-52G-39@gated-at.bofh.it> <rrNbB-57Y-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 04/25/2016 07:48 AM, Christoph Hellwig wrote:
> On Thu, Apr 21, 2016 at 02:15:24PM -0400, Waiman Long wrote:
>> On 04/20/2016 04:58 PM, Christoph Hellwig wrote:
>>> FYI, none of the Dax code even needs to ever touch the dio_count,
>>> as dax I/O can't be asynchronous, and we thus don't need it to protect
>>> against truncate.  I'd suggest to remove it and then end_io callback
>> >from the DAX code entirely as a start and then move from there.
>>
>> Yes, it seems like we may not need to change the dio_count in dax_do_io()
>> after all. BTW, what do mean by using end_io callback as a start?
> I mean to remove both the i_dio_count manipulation, and the unessecary
> end_io callback from dax_do_io.

Thanks for the clarification.

Since DAX I/O is always synchronous, the locking done by the caller or 
in the dax_do_Io() for read should be enough to prevent truncation from 
happening at the same time. So we don't need to use i_dio_count for that 
purpose.

However, I have not understood enough of the block IO layer to determine 
if the end_io callback is really redundant. I am not confident enough to 
touch the end_io callback.

Cheers,
Longman

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if  inode_dio_begin() called Christoph Hellwig <hch@infradead.org> - 2016-04-20 23:00 +0200
  Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin()  called Waiman Long <waiman.long@hpe.com> - 2016-04-21 20:20 +0200
    Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if  inode_dio_begin() called Christoph Hellwig <hch@infradead.org> - 2016-04-25 13:50 +0200
      Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin()  called Waiman Long <waiman.long@hpe.com> - 2016-04-26 18:40 +0200

csiph-web