From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5502FC433E0 for ; Tue, 23 Feb 2021 10:33:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0775864E4B for ; Tue, 23 Feb 2021 10:33:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231701AbhBWKcp (ORCPT ); Tue, 23 Feb 2021 05:32:45 -0500 Received: from mx2.suse.de ([195.135.220.15]:41266 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229864AbhBWKcK (ORCPT ); Tue, 23 Feb 2021 05:32:10 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 95D35ADD6; Tue, 23 Feb 2021 10:31:27 +0000 (UTC) Received: from localhost (brahms [local]) by brahms (OpenSMTPD) with ESMTPA id eea028fc; Tue, 23 Feb 2021 10:32:32 +0000 (UTC) Date: Tue, 23 Feb 2021 10:32:32 +0000 From: Luis Henriques To: dai.ngo@oracle.com Cc: Amir Goldstein , Jeff Layton , Steve French , Miklos Szeredi , Trond Myklebust , Anna Schumaker , Alexander Viro , "Darrick J. Wong" , Dave Chinner , Greg KH , Nicolas Boichat , Ian Lance Taylor , Luis Lozano , Andreas Dilger , Olga Kornievskaia , Christoph Hellwig , ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH v8] vfs: fix copy_file_range regression in cross-fs copies Message-ID: References: <20210221195833.23828-1-lhenriques@suse.de> <20210222102456.6692-1-lhenriques@suse.de> <26a22719-427a-75cf-92eb-dda10d442ded@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <26a22719-427a-75cf-92eb-dda10d442ded@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 22, 2021 at 08:25:27AM -0800, dai.ngo@oracle.com wrote: > > On 2/22/21 2:24 AM, Luis Henriques wrote: > > A regression has been reported by Nicolas Boichat, found while using the > > copy_file_range syscall to copy a tracefs file. Before commit > > 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") the > > kernel would return -EXDEV to userspace when trying to copy a file across > > different filesystems. After this commit, the syscall doesn't fail anymore > > and instead returns zero (zero bytes copied), as this file's content is > > generated on-the-fly and thus reports a size of zero. > > > > This patch restores some cross-filesystem copy restrictions that existed > > prior to commit 5dae222a5ff0 ("vfs: allow copy_file_range to copy across > > devices"). Filesystems are still allowed to fall-back to the VFS > > generic_copy_file_range() implementation, but that has now to be done > > explicitly. > > > > nfsd is also modified to fall-back into generic_copy_file_range() in case > > vfs_copy_file_range() fails with -EOPNOTSUPP or -EXDEV. > > > > Fixes: 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") > > Link: https://urldefense.com/v3/__https://lore.kernel.org/linux-fsdevel/20210212044405.4120619-1-drinkcat@chromium.org/__;!!GqivPVa7Brio!P1UWThiSkxbjfjFQWNYJmCxGEkiLFyvHjH6cS-G1ZTt1z-TeqwGQgQmi49dC6w$ > > Link: https://urldefense.com/v3/__https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx*BnvW=ZmpsG47CyHFJwnw7zSX6Q@mail.gmail.com/__;Kw!!GqivPVa7Brio!P1UWThiSkxbjfjFQWNYJmCxGEkiLFyvHjH6cS-G1ZTt1z-TeqwGQgQmgCmMHzA$ > > Link: https://urldefense.com/v3/__https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/__;!!GqivPVa7Brio!P1UWThiSkxbjfjFQWNYJmCxGEkiLFyvHjH6cS-G1ZTt1z-TeqwGQgQmzqItkrQ$ > > Reported-by: Nicolas Boichat > > Signed-off-by: Luis Henriques > > --- > > Changes since v7 > > - set 'ret' to '-EOPNOTSUPP' before the clone 'if' statement so that the > > error returned is always related to the 'copy' operation > > Changes since v6 > > - restored i_sb checks for the clone operation > > Changes since v5 > > - check if ->copy_file_range is NULL before calling it > > Changes since v4 > > - nfsd falls-back to generic_copy_file_range() only *if* it gets -EOPNOTSUPP > > or -EXDEV. > > Changes since v3 > > - dropped the COPY_FILE_SPLICE flag > > - kept the f_op's checks early in generic_copy_file_checks, implementing > > Amir's suggestions > > - modified nfsd to use generic_copy_file_range() > > Changes since v2 > > - do all the required checks earlier, in generic_copy_file_checks(), > > adding new checks for ->remap_file_range > > - new COPY_FILE_SPLICE flag > > - don't remove filesystem's fallback to generic_copy_file_range() > > - updated commit changelog (and subject) > > Changes since v1 (after Amir review) > > - restored do_copy_file_range() helper > > - return -EOPNOTSUPP if fs doesn't implement CFR > > - updated commit description > > > > fs/nfsd/vfs.c | 8 +++++++- > > fs/read_write.c | 49 ++++++++++++++++++++++++------------------------- > > 2 files changed, 31 insertions(+), 26 deletions(-) > > > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > > index 04937e51de56..23dab0fa9087 100644 > > --- a/fs/nfsd/vfs.c > > +++ b/fs/nfsd/vfs.c > > @@ -568,6 +568,7 @@ __be32 nfsd4_clone_file_range(struct nfsd_file *nf_src, u64 src_pos, > > ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst, > > u64 dst_pos, u64 count) > > { > > + ssize_t ret; > > /* > > * Limit copy to 4MB to prevent indefinitely blocking an nfsd > > @@ -578,7 +579,12 @@ ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst, > > * limit like this and pipeline multiple COPY requests. > > */ > > count = min_t(u64, count, 1 << 22); > > - return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0); > > + ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0); > > + > > + if (ret == -EOPNOTSUPP || ret == -EXDEV) > > + ret = generic_copy_file_range(src, src_pos, dst, dst_pos, > > + count, 0); > > + return ret; > > } > > __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp, > > diff --git a/fs/read_write.c b/fs/read_write.c > > index 75f764b43418..5a26297fd410 100644 > > --- a/fs/read_write.c > > +++ b/fs/read_write.c > > @@ -1388,28 +1388,6 @@ ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in, > > } > > EXPORT_SYMBOL(generic_copy_file_range); > > -static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in, > > - struct file *file_out, loff_t pos_out, > > - size_t len, unsigned int flags) > > -{ > > - /* > > - * Although we now allow filesystems to handle cross sb copy, passing > > - * a file of the wrong filesystem type to filesystem driver can result > > - * in an attempt to dereference the wrong type of ->private_data, so > > - * avoid doing that until we really have a good reason. NFS defines > > - * several different file_system_type structures, but they all end up > > - * using the same ->copy_file_range() function pointer. > > - */ > > - if (file_out->f_op->copy_file_range && > > - file_out->f_op->copy_file_range == file_in->f_op->copy_file_range) > > - return file_out->f_op->copy_file_range(file_in, pos_in, > > - file_out, pos_out, > > - len, flags); > > - > > - return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len, > > - flags); > > -} > > - > > /* > > * Performs necessary checks before doing a file copy > > * > > @@ -1427,6 +1405,25 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in, > > loff_t size_in; > > int ret; > > + /* > > + * Although we now allow filesystems to handle cross sb copy, passing > > + * a file of the wrong filesystem type to filesystem driver can result > > + * in an attempt to dereference the wrong type of ->private_data, so > > + * avoid doing that until we really have a good reason. NFS defines > > + * several different file_system_type structures, but they all end up > > + * using the same ->copy_file_range() function pointer. > > + */ > > + if (file_out->f_op->copy_file_range) { > > + if (file_in->f_op->copy_file_range != > > + file_out->f_op->copy_file_range) > > + return -EXDEV; > > + } else if (file_in->f_op->remap_file_range) { > > + if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb) > > + return -EXDEV; > > I think this check is redundant, it's done in vfs_copy_file_range. > If this check is removed then the else clause below should be removed > also. Once this check and the else clause are removed then might as > well move the the check of copy_file_range from here to vfs_copy_file_range. > I don't think it's really redundant, although I agree is messy due to the fact we try to clone first instead of copying them. So, in the clone path, this is the only place where we return -EXDEV if: 1) we don't have ->copy_file_range *and* 2) we have ->remap_file_range but the i_sb are different. The check in vfs_copy_file_range() is only executed if: 1) we have *valid* ->copy_file_range ops and/or 2) we have *valid* ->remap_file_range So... if we remove the check in generic_copy_file_checks() as you suggest and: - we don't have ->copy_file_range, - we have ->remap_file_range but - the i_sb are different we'll return the -EOPNOTSUPP (the one set in line "ret = -EOPNOTSUPP;" in function vfs_copy_file_range() ) instead of -EXDEV. But I may have got it all wrong. I've looked so many times at this code that I'm probably useless at finding problems in it :-) Cheers, -- Luís > -Dai > > > + } else { > > + return -EOPNOTSUPP; > > + } > > + > > ret = generic_file_rw_checks(file_in, file_out); > > if (ret) > > return ret; > > @@ -1495,6 +1492,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, > > file_start_write(file_out); > > + ret = -EOPNOTSUPP; > > /* > > * Try cloning first, this is supported by more file systems, and > > * more efficient if both clone and copy are supported (e.g. NFS). > > @@ -1513,9 +1511,10 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, > > } > > } > > - ret = do_copy_file_range(file_in, pos_in, file_out, pos_out, len, > > - flags); > > - WARN_ON_ONCE(ret == -EOPNOTSUPP); > > + if (file_out->f_op->copy_file_range) > > + ret = file_out->f_op->copy_file_range(file_in, pos_in, > > + file_out, pos_out, > > + len, flags); > > done: > > if (ret > 0) { > > fsnotify_access(file_in);