From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx144.netapp.com ([216.240.21.25]:47024 "EHLO mx144.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753574AbbJNR7o (ORCPT ); Wed, 14 Oct 2015 13:59:44 -0400 Subject: Re: [PATCH v5 8/9] vfs: Add vfs_copy_file_range() support for pagecache copies To: Christoph Hellwig References: <1443634014-3026-1-git-send-email-Anna.Schumaker@Netapp.com> <1443634014-3026-9-git-send-email-Anna.Schumaker@Netapp.com> <20151011142203.GA31867@infradead.org> <20151012231749.GC11398@birch.djwong.org> CC: "Darrick J. Wong" , , , , , , , , , From: Anna Schumaker Message-ID: <561E980C.9010509@Netapp.com> Date: Wed, 14 Oct 2015 13:59:40 -0400 MIME-Version: 1.0 In-Reply-To: <20151012231749.GC11398@birch.djwong.org> Content-Type: text/plain; charset="utf-8" Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/12/2015 07:17 PM, Darrick J. Wong wrote: > On Sun, Oct 11, 2015 at 07:22:03AM -0700, Christoph Hellwig wrote: >> On Wed, Sep 30, 2015 at 01:26:52PM -0400, Anna Schumaker wrote: >>> This allows us to have an in-kernel copy mechanism that avoids frequent >>> switches between kernel and user space. This is especially useful so >>> NFSD can support server-side copies. >>> >>> I make pagecache copies configurable by adding three new (exclusive) >>> flags: >>> - COPY_FR_REFLINK tells vfs_copy_file_range() to only create a reflink. >>> - COPY_FR_COPY does a full data copy, but may be filesystem accelerated. >>> - COPY_FR_DEDUP creates a reflink, but only if the contents of both >>> ranges are identical. >> >> All but FR_COPY really should be a separate system call. Clones (an >> dedup as a special case of clones) are really a separate beast from file >> copies. >> >> If I want to clone a file I either want it clone fully or fail, not copy >> a certain amount. That means that a) we need to return an error not >> short "write", and b) locking impementations are important - we need to >> prevent other applications from racing with our clone even if it is >> large, while to get these semantics for the possible short returning >> file copy will require a proper userland locking protocol. Last but not >> least file copies need to be interruptible while clones should be not. >> All this is already important for local file systems and even more >> important for NFS exporting. >> >> So I'd suggest to drop this patch and just let your syscall handle >> actualy copies with all their horrors. We can go with Peng's patches >> to generalize the btrfs ioctls for clones for now which is what everyone >> already uses anyway, and then add a separate sys_file_clone later. So what I'm hearing is that I should drop the reflink and dedup flags and change this system call only perform a full copy (with preserving of sparseness), correct? I can make those changes, but only if everybody is in agreement that it's the best way forward. The only reason I haven't done anything to make this system call interruptible is because I haven't been able to find any documentation or examples for making system calls interruptible. How do I do this? Anna > > Hm. Peng's patches only generalize the CLONE and CLONE_RANGE ioctls from > btrfs, however they don't port over the (vastly different) EXTENT_SAME ioctl. > > What does everyone think about generalizing EXTENT_SAME? The interface enables > one to ask the kernel to dedupe multiple file ranges in a single call. That's > more complex than what I was proposing with COPY_FR_DEDUP(E), but I'm assuming > that the extra complexity buys us the ability to ... multi-dedupe at the same > time, with locks held on the source file? > > I'm happy to generalize the existing EXTENT_SAME, but please yell if you really > hate the interface. > > --D > >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-api" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anna Schumaker Subject: Re: [PATCH v5 8/9] vfs: Add vfs_copy_file_range() support for pagecache copies Date: Wed, 14 Oct 2015 13:59:40 -0400 Message-ID: <561E980C.9010509@Netapp.com> References: <1443634014-3026-1-git-send-email-Anna.Schumaker@Netapp.com> <1443634014-3026-9-git-send-email-Anna.Schumaker@Netapp.com> <20151011142203.GA31867@infradead.org> <20151012231749.GC11398@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: "Darrick J. Wong" , , , , , , , , , To: Christoph Hellwig Return-path: In-Reply-To: <20151012231749.GC11398-PTl6brltDGh4DFYR7WNSRA@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On 10/12/2015 07:17 PM, Darrick J. Wong wrote: > On Sun, Oct 11, 2015 at 07:22:03AM -0700, Christoph Hellwig wrote: >> On Wed, Sep 30, 2015 at 01:26:52PM -0400, Anna Schumaker wrote: >>> This allows us to have an in-kernel copy mechanism that avoids frequent >>> switches between kernel and user space. This is especially useful so >>> NFSD can support server-side copies. >>> >>> I make pagecache copies configurable by adding three new (exclusive) >>> flags: >>> - COPY_FR_REFLINK tells vfs_copy_file_range() to only create a reflink. >>> - COPY_FR_COPY does a full data copy, but may be filesystem accelerated. >>> - COPY_FR_DEDUP creates a reflink, but only if the contents of both >>> ranges are identical. >> >> All but FR_COPY really should be a separate system call. Clones (an >> dedup as a special case of clones) are really a separate beast from file >> copies. >> >> If I want to clone a file I either want it clone fully or fail, not copy >> a certain amount. That means that a) we need to return an error not >> short "write", and b) locking impementations are important - we need to >> prevent other applications from racing with our clone even if it is >> large, while to get these semantics for the possible short returning >> file copy will require a proper userland locking protocol. Last but not >> least file copies need to be interruptible while clones should be not. >> All this is already important for local file systems and even more >> important for NFS exporting. >> >> So I'd suggest to drop this patch and just let your syscall handle >> actualy copies with all their horrors. We can go with Peng's patches >> to generalize the btrfs ioctls for clones for now which is what everyone >> already uses anyway, and then add a separate sys_file_clone later. So what I'm hearing is that I should drop the reflink and dedup flags and change this system call only perform a full copy (with preserving of sparseness), correct? I can make those changes, but only if everybody is in agreement that it's the best way forward. The only reason I haven't done anything to make this system call interruptible is because I haven't been able to find any documentation or examples for making system calls interruptible. How do I do this? Anna > > Hm. Peng's patches only generalize the CLONE and CLONE_RANGE ioctls from > btrfs, however they don't port over the (vastly different) EXTENT_SAME ioctl. > > What does everyone think about generalizing EXTENT_SAME? The interface enables > one to ask the kernel to dedupe multiple file ranges in a single call. That's > more complex than what I was proposing with COPY_FR_DEDUP(E), but I'm assuming > that the extra complexity buys us the ability to ... multi-dedupe at the same > time, with locks held on the source file? > > I'm happy to generalize the existing EXTENT_SAME, but please yell if you really > hate the interface. > > --D > >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-api" in >> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anna Schumaker Subject: Re: [PATCH v5 8/9] vfs: Add vfs_copy_file_range() support for pagecache copies Date: Wed, 14 Oct 2015 13:59:40 -0400 Message-ID: <561E980C.9010509@Netapp.com> References: <1443634014-3026-1-git-send-email-Anna.Schumaker@Netapp.com> <1443634014-3026-9-git-send-email-Anna.Schumaker@Netapp.com> <20151011142203.GA31867@infradead.org> <20151012231749.GC11398@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151012231749.GC11398-PTl6brltDGh4DFYR7WNSRA@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig Cc: "Darrick J. Wong" , linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, zab-ugsP4Wv/S6ZeoWH0uzbU5w@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, clm-b10kYP2dOMg@public.gmane.org, mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, andros-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org List-Id: linux-api@vger.kernel.org On 10/12/2015 07:17 PM, Darrick J. Wong wrote: > On Sun, Oct 11, 2015 at 07:22:03AM -0700, Christoph Hellwig wrote: >> On Wed, Sep 30, 2015 at 01:26:52PM -0400, Anna Schumaker wrote: >>> This allows us to have an in-kernel copy mechanism that avoids frequent >>> switches between kernel and user space. This is especially useful so >>> NFSD can support server-side copies. >>> >>> I make pagecache copies configurable by adding three new (exclusive) >>> flags: >>> - COPY_FR_REFLINK tells vfs_copy_file_range() to only create a reflink. >>> - COPY_FR_COPY does a full data copy, but may be filesystem accelerated. >>> - COPY_FR_DEDUP creates a reflink, but only if the contents of both >>> ranges are identical. >> >> All but FR_COPY really should be a separate system call. Clones (an >> dedup as a special case of clones) are really a separate beast from file >> copies. >> >> If I want to clone a file I either want it clone fully or fail, not copy >> a certain amount. That means that a) we need to return an error not >> short "write", and b) locking impementations are important - we need to >> prevent other applications from racing with our clone even if it is >> large, while to get these semantics for the possible short returning >> file copy will require a proper userland locking protocol. Last but not >> least file copies need to be interruptible while clones should be not. >> All this is already important for local file systems and even more >> important for NFS exporting. >> >> So I'd suggest to drop this patch and just let your syscall handle >> actualy copies with all their horrors. We can go with Peng's patches >> to generalize the btrfs ioctls for clones for now which is what everyone >> already uses anyway, and then add a separate sys_file_clone later. So what I'm hearing is that I should drop the reflink and dedup flags and change this system call only perform a full copy (with preserving of sparseness), correct? I can make those changes, but only if everybody is in agreement that it's the best way forward. The only reason I haven't done anything to make this system call interruptible is because I haven't been able to find any documentation or examples for making system calls interruptible. How do I do this? Anna > > Hm. Peng's patches only generalize the CLONE and CLONE_RANGE ioctls from > btrfs, however they don't port over the (vastly different) EXTENT_SAME ioctl. > > What does everyone think about generalizing EXTENT_SAME? The interface enables > one to ask the kernel to dedupe multiple file ranges in a single call. That's > more complex than what I was proposing with COPY_FR_DEDUP(E), but I'm assuming > that the extra complexity buys us the ability to ... multi-dedupe at the same > time, with locks held on the source file? > > I'm happy to generalize the existing EXTENT_SAME, but please yell if you really > hate the interface. > > --D > >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-api" in >> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html