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Date: Mon, 18 Apr 2016 15:46:46 -0400 From: Waiman Long <waiman.long@....com> To: Dave Chinner <david@...morbit.com> CC: Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>, Scott J Norton <scott.norton@....com>, Douglas Hatch <doug.hatch@....com>, Toshimitsu Kani <toshi.kani@....com> Subject: Re: [PATCH v3 1/2] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin() called On 04/15/2016 06:19 PM, Dave Chinner wrote: > On Fri, Apr 15, 2016 at 01:17:41PM -0400, Waiman Long wrote: >> On 04/15/2016 04:17 AM, Dave Chinner wrote: >>> On Thu, Apr 14, 2016 at 12:21:13PM -0400, Waiman Long wrote: >>>> What the patch does is to eliminate the innermost >>>> inode_dio_begin/end pair. >>> Yes, and with that change inode_dio_wait() no longer waits for >>> AIO+DIO writes on ext4, hence breaking truncate IO barrier >>> requirements of inode_dio_wait(). >>> >>> Cheers, >>> >>> Dave. >> You are right and thank for pointing this out to me. I think I focus too >> much on the dax_do_io() internal and didn't realize that inode_dio_end() can >> be deferred in __blockdev_direct_IO(). I will update my patch to eliminate >> the extra inode_dio_begin/end pair only for dax_do_io(). > Even there there is the risk that a future change will break ext4. > the ext4 code needs fixing first, then you can look at skipping the > DIO based counting everywhere. > > i.e. fix the root cause of the problem, don't hack around it or > throw band-aids over it. > > Cheers, > > Dave. I agree that the ext4 code needs fixing w.r.t. the problem that you found. That will take more time and testing. In the mean time, I think it is OK to pick the low-hanging fruits that are handled by my patch. Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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