From: Jeff Moyer <jmoyer@redhat.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
ocfs2-devel@oss.oracle.com, xfs@oss.sgi.com
Subject: Re: vfs/xfs: directio updates to ease COW handling V2
Date: Wed, 03 Feb 2016 16:53:04 -0500 [thread overview]
Message-ID: <x49twlpxxz3.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20160203200159.GK20038@birch.djwong.org> (Darrick J. Wong's message of "Wed, 3 Feb 2016 12:01:59 -0800")
"Darrick J. Wong" <darrick.wong@oracle.com> writes:
> On Wed, Feb 03, 2016 at 02:43:02PM -0500, Jeff Moyer wrote:
>> Hi, Christoph,
>>
>> Can you explain a bit what you mean by easing COW handling? Whenever I
>> see COW referenced near DIO, my mind always turns to g_u_p vs. fork.
>
> Just to clarify, I'm talking about copy on write for disk blocks, not for
> memory pages.
>
> Basically, XFS implements (disk block) copy on write for (perfectly block
> aligned) directio writes by allocating a set of replacement blocks, mapping the
> dio writes to the new blocks, and playing a punch/remap trick to map the new
> blocks into the file at the appropriate offset.
>
> If the write fails then we don't want do the remap, so the dio_complete handler
> has to know whether or not the IO succeeded, hence the new parameter.
> Furthermore, if the write succeeds but the remap fails, we also want to be able
> to report that to userspace, hence the change of return value from void to int.
>
> (If the dio write isn't block aligned, we fall back to the page cache.)
>
> Hope that helps,
Eric said the magic word: reflink. I think I've got it now.
Thanks!
Jeff
WARNING: multiple messages have this Message-ID (diff)
From: Jeff Moyer <jmoyer@redhat.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
Christoph Hellwig <hch@lst.de>,
ocfs2-devel@oss.oracle.com, xfs@oss.sgi.com
Subject: Re: vfs/xfs: directio updates to ease COW handling V2
Date: Wed, 03 Feb 2016 16:53:04 -0500 [thread overview]
Message-ID: <x49twlpxxz3.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20160203200159.GK20038@birch.djwong.org> (Darrick J. Wong's message of "Wed, 3 Feb 2016 12:01:59 -0800")
"Darrick J. Wong" <darrick.wong@oracle.com> writes:
> On Wed, Feb 03, 2016 at 02:43:02PM -0500, Jeff Moyer wrote:
>> Hi, Christoph,
>>
>> Can you explain a bit what you mean by easing COW handling? Whenever I
>> see COW referenced near DIO, my mind always turns to g_u_p vs. fork.
>
> Just to clarify, I'm talking about copy on write for disk blocks, not for
> memory pages.
>
> Basically, XFS implements (disk block) copy on write for (perfectly block
> aligned) directio writes by allocating a set of replacement blocks, mapping the
> dio writes to the new blocks, and playing a punch/remap trick to map the new
> blocks into the file at the appropriate offset.
>
> If the write fails then we don't want do the remap, so the dio_complete handler
> has to know whether or not the IO succeeded, hence the new parameter.
> Furthermore, if the write succeeds but the remap fails, we also want to be able
> to report that to userspace, hence the change of return value from void to int.
>
> (If the dio write isn't block aligned, we fall back to the page cache.)
>
> Hope that helps,
Eric said the magic word: reflink. I think I've got it now.
Thanks!
Jeff
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
WARNING: multiple messages have this Message-ID (diff)
From: Jeff Moyer <jmoyer@redhat.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
ocfs2-devel@oss.oracle.com, xfs@oss.sgi.com
Subject: [Ocfs2-devel] vfs/xfs: directio updates to ease COW handling V2
Date: Wed, 03 Feb 2016 16:53:04 -0500 [thread overview]
Message-ID: <x49twlpxxz3.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20160203200159.GK20038@birch.djwong.org> (Darrick J. Wong's message of "Wed, 3 Feb 2016 12:01:59 -0800")
"Darrick J. Wong" <darrick.wong@oracle.com> writes:
> On Wed, Feb 03, 2016 at 02:43:02PM -0500, Jeff Moyer wrote:
>> Hi, Christoph,
>>
>> Can you explain a bit what you mean by easing COW handling? Whenever I
>> see COW referenced near DIO, my mind always turns to g_u_p vs. fork.
>
> Just to clarify, I'm talking about copy on write for disk blocks, not for
> memory pages.
>
> Basically, XFS implements (disk block) copy on write for (perfectly block
> aligned) directio writes by allocating a set of replacement blocks, mapping the
> dio writes to the new blocks, and playing a punch/remap trick to map the new
> blocks into the file at the appropriate offset.
>
> If the write fails then we don't want do the remap, so the dio_complete handler
> has to know whether or not the IO succeeded, hence the new parameter.
> Furthermore, if the write succeeds but the remap fails, we also want to be able
> to report that to userspace, hence the change of return value from void to int.
>
> (If the dio write isn't block aligned, we fall back to the page cache.)
>
> Hope that helps,
Eric said the magic word: reflink. I think I've got it now.
Thanks!
Jeff
next prev parent reply other threads:[~2016-02-03 21:53 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 18:40 vfs/xfs: directio updates to ease COW handling V2 Christoph Hellwig
2016-02-03 18:40 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-03 18:40 ` Christoph Hellwig
2016-02-03 18:40 ` [PATCH 1/3] direct-io: always call ->end_io if non-NULL Christoph Hellwig
2016-02-03 18:40 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-03 18:40 ` Christoph Hellwig
2016-02-03 19:55 ` Darrick J. Wong
2016-02-03 19:55 ` [Ocfs2-devel] " Darrick J. Wong
2016-02-03 19:55 ` Darrick J. Wong
2016-02-04 7:14 ` Christoph Hellwig
2016-02-04 7:14 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-04 7:14 ` Christoph Hellwig
2016-02-04 8:17 ` Darrick J. Wong
2016-02-04 8:17 ` [Ocfs2-devel] " Darrick J. Wong
2016-02-04 8:17 ` Darrick J. Wong
2016-02-03 18:40 ` [PATCH 2/3] xfs: don't use ioends for direct write completions Christoph Hellwig
2016-02-03 18:40 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-03 18:40 ` Christoph Hellwig
2016-02-05 21:57 ` Darrick J. Wong
2016-02-05 21:57 ` [Ocfs2-devel] " Darrick J. Wong
2016-02-05 21:57 ` Darrick J. Wong
2016-02-05 22:36 ` Dave Chinner
2016-02-05 22:36 ` [Ocfs2-devel] " Dave Chinner
2016-02-05 22:36 ` Dave Chinner
2016-02-08 1:00 ` Dave Chinner
2016-02-08 1:00 ` [Ocfs2-devel] " Dave Chinner
2016-02-08 1:00 ` Dave Chinner
2016-02-08 6:17 ` Dave Chinner
2016-02-08 6:17 ` [Ocfs2-devel] " Dave Chinner
2016-02-08 6:17 ` Dave Chinner
2016-02-08 7:31 ` Christoph Hellwig
2016-02-08 7:31 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-08 7:31 ` Christoph Hellwig
2016-02-08 9:16 ` Dave Chinner
2016-02-08 9:16 ` [Ocfs2-devel] " Dave Chinner
2016-02-08 9:16 ` Dave Chinner
2016-02-08 9:22 ` Christoph Hellwig
2016-02-08 9:22 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-08 9:22 ` Christoph Hellwig
2016-02-03 18:40 ` [PATCH 3/3] xfs: fold xfs_vm_do_dio into xfs_vm_direct_IO Christoph Hellwig
2016-02-03 18:40 ` [Ocfs2-devel] " Christoph Hellwig
2016-02-03 18:40 ` Christoph Hellwig
2016-02-03 18:40 ` Christoph Hellwig
2016-02-03 19:43 ` vfs/xfs: directio updates to ease COW handling V2 Jeff Moyer
2016-02-03 19:43 ` [Ocfs2-devel] " Jeff Moyer
2016-02-03 19:43 ` Jeff Moyer
2016-02-03 20:01 ` Darrick J. Wong
2016-02-03 20:01 ` [Ocfs2-devel] " Darrick J. Wong
2016-02-03 20:01 ` Darrick J. Wong
2016-02-03 21:53 ` Jeff Moyer [this message]
2016-02-03 21:53 ` [Ocfs2-devel] " Jeff Moyer
2016-02-03 21:53 ` Jeff Moyer
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