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From: dai.ngo@oracle.com
To: Luis Henriques <lhenriques@suse.de>
Cc: Amir Goldstein <amir73il@gmail.com>,
	Jeff Layton <jlayton@kernel.org>,
	Steve French <sfrench@samba.org>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Trond Myklebust <trond.myklebust@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Dave Chinner <dchinner@redhat.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Nicolas Boichat <drinkcat@chromium.org>,
	Ian Lance Taylor <iant@google.com>,
	Luis Lozano <llozano@chromium.org>,
	Andreas Dilger <adilger@dilger.ca>,
	Olga Kornievskaia <aglo@umich.edu>,
	Christoph Hellwig <hch@infradead.org>,
	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
Date: Tue, 23 Feb 2021 07:29:09 -0800	[thread overview]
Message-ID: <7cc69c24-80dd-0053-24b9-3a28b0153f7e@oracle.com> (raw)
In-Reply-To: <YDTZwH7xv41Wimax@suse.de>


On 2/23/21 2:32 AM, Luis Henriques wrote:
> 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 <drinkcat@chromium.org>
>>> Signed-off-by: Luis Henriques <lhenriques@suse.de>
>>> ---
>>> 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.

Yes, this is the different.The NFS code handles both -EOPNOTSUPP and
-EXDEVV by doing generic_copy_file_range.  Do any other consumers of
vfs_copy_file_range rely on -EXDEV and not -EOPNOTSUPP and which is
the correct error code for this case? It seems to me that -EOPNOTSUPP
is more appropriate than EXDEV when (sb1 != sb2).

>
> 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 :-)

You're not alone, we all try to do the right thing :-)

-Dai

>
> 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);

  parent reply	other threads:[~2021-02-23 15:31 UTC|newest]

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-12  4:43 [PATCH 0/6] Add generated flag to filesystem struct to block copy_file_range Nicolas Boichat
2021-02-12  4:44 ` [PATCH 1/6] fs: Add flag to file_system_type to indicate content is generated Nicolas Boichat
2021-02-12  7:46   ` Greg KH
2021-02-12  8:20     ` Nicolas Boichat
2021-02-12  8:37       ` Greg KH
2021-02-12 15:33         ` Ian Lance Taylor
2021-02-12 15:45           ` Greg KH
2021-02-12 15:59             ` Ian Lance Taylor
2021-02-12 16:28               ` Greg KH
2021-02-12 20:22                 ` Ian Lance Taylor
2021-02-12 23:03             ` Dave Chinner
2021-02-12 23:07               ` Ian Lance Taylor
2021-02-12 23:27                 ` Dave Chinner
2021-02-12 23:54                   ` Darrick J. Wong
2021-02-15  0:38                     ` Dave Chinner
2021-02-15  1:12                       ` Ian Lance Taylor
2021-02-15  1:25                         ` Nicolas Boichat
2021-02-15  5:56                           ` Amir Goldstein
2021-02-15  8:30                           ` Greg KH
2021-02-12  8:22     ` Amir Goldstein
2021-02-12  8:39       ` Greg KH
2021-02-12 12:05         ` Luis Henriques
2021-02-12 12:18           ` Greg KH
2021-02-12 12:41             ` Luis Henriques
2021-02-12 14:11               ` Greg KH
2021-02-12 15:01                 ` Luis Henriques
2021-02-15  6:12               ` Amir Goldstein
2021-02-15 10:39                 ` Luis Henriques
2021-02-15 12:22                   ` Luis Henriques
2021-02-15 14:23                     ` Amir Goldstein
2021-02-15 14:51                       ` Luis Henriques
2021-02-15 15:43                       ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Luis Henriques
2021-02-15 16:02                         ` Trond Myklebust
2021-02-16  0:25                           ` Steve French
2021-02-15 16:34                         ` Amir Goldstein
2021-02-15 16:53                           ` Trond Myklebust
2021-02-15 17:24                             ` Amir Goldstein
2021-02-15 18:57                               ` Trond Myklebust
2021-02-15 19:43                                 ` Amir Goldstein
2021-02-16 11:17                                   ` Luis Henriques
2021-02-16 11:28                                     ` gregkh
2021-02-16 12:01                                       ` Luis Henriques
2021-02-16 12:08                                         ` Greg KH
2021-02-16 13:51                                     ` Amir Goldstein
2021-02-16 16:42                                       ` Luis Henriques
2021-02-16 17:44                                         ` Amir Goldstein
2021-02-16 18:55                                           ` Luis Henriques
2021-02-16 19:20                                             ` Amir Goldstein
2021-02-16 19:27                                               ` Anna Schumaker
2021-02-16 19:31                                                 ` Steve French
2021-02-16 19:40                                                   ` Amir Goldstein
2021-02-16 21:15                                                     ` Steve French
2021-02-17  8:08                                                       ` Amir Goldstein
2021-02-17 17:26                                                         ` [PATCH v3] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-17 20:47                                                           ` Amir Goldstein
2021-02-18  0:56                                                           ` Nicolas Boichat
2021-02-18  5:32                                                           ` Olga Kornievskaia
2021-02-18  6:47                                                             ` Amir Goldstein
2021-02-18 16:28                                                               ` Olga Kornievskaia
2021-02-18  7:43                                                           ` Christoph Hellwig
2021-02-18  0:50                                                         ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Andreas Dilger
2021-02-18  7:34                                                           ` gregkh
2021-02-16 18:54                                       ` Andreas Dilger
2021-02-17  4:45                         ` Nicolas Boichat
2021-02-18  7:42                         ` Christoph Hellwig
2021-02-18  9:10                           ` Amir Goldstein
2021-02-18 10:29                             ` Luis Henriques
2021-02-18 12:15                               ` Luis Henriques
2021-02-18 12:49                                 ` Amir Goldstein
2021-02-18 14:36                                   ` [PATCH v4] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-18 14:58                                     ` Amir Goldstein
2021-02-18 15:17                                       ` [PATCH v5] " Luis Henriques
2021-02-18 15:53                                         ` Amir Goldstein
2021-02-18 16:35                                           ` Luis Henriques
2021-02-18 17:18                                             ` [PATCH v6] " Luis Henriques
2021-02-19 21:18                                               ` Olga Kornievskaia
2021-02-19 21:52                                                 ` Amir Goldstein
2021-02-21 19:58                                                 ` [PATCH v7] " Luis Henriques
2021-02-22  3:00                                                   ` Nicolas Boichat
2021-02-22 10:24                                                   ` [PATCH v8] " Luis Henriques
2021-02-22 10:46                                                     ` Amir Goldstein
2021-02-22 16:25                                                     ` dai.ngo
2021-02-23 10:32                                                       ` Luis Henriques
2021-02-23 15:28                                                         ` Amir Goldstein
2021-02-23 15:29                                                         ` dai.ngo [this message]
2021-02-23 16:02                                                           ` dai.ngo
2021-02-23 16:47                                                             ` Amir Goldstein
2021-02-23 16:57                                                               ` dai.ngo
     [not found]                                                                 ` <e3eed18b-fc7e-e687-608b-7f662017329c@oracle.com>
2021-02-23 17:33                                                                   ` Amir Goldstein
2021-02-24  0:13                                                                     ` dai.ngo
2021-02-23 17:56                                                                 ` Luis Henriques
2021-02-23 17:13                                                             ` Olga Kornievskaia
2021-02-24  1:00                                                     ` Olga Kornievskaia
2021-02-24 10:23                                                       ` Luis Henriques
2021-02-24 10:44                                                         ` Nicolas Boichat
2021-04-09  5:23                                                           ` Nicolas Boichat
2021-04-09 13:39                                                             ` Luis Henriques
2021-04-09 13:50                                                               ` Amir Goldstein
2021-04-23  4:40                                                                 ` Nicolas Boichat
2021-05-03  8:54                                                                   ` Luis Henriques
2021-05-10  4:59                                                                     ` Amir Goldstein
2021-05-10  9:10                                                                       ` Luis Henriques
2021-02-24 14:23                                                     ` [PATCH] copy_file_range.2: Kernel v5.12 updates Luis Henriques
2021-02-24 16:10                                                       ` Amir Goldstein
2021-02-25 10:21                                                         ` Luis Henriques
2021-02-26 10:13                                                           ` Alejandro Colomar (man-pages)
2021-02-26 10:34                                                             ` Amir Goldstein
2021-02-26 11:15                                                               ` Alejandro Colomar (man-pages)
2021-02-26 13:59                                                                 ` Jeff Layton
2021-02-26 21:26                                                                   ` Alejandro Colomar (man-pages)
2021-02-26 22:18                                                         ` Alejandro Colomar (man-pages)
2021-02-27  5:41                                                           ` Amir Goldstein
2021-02-27 12:20                                                             ` Alejandro Colomar (man-pages)
2021-02-27 13:49                                                               ` [RFC v2] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-02-27 16:00                                                                 ` Amir Goldstein
2021-02-27 23:08                                                             ` [PATCH] copy_file_range.2: Kernel v5.12 updates Steve French
2021-02-28  7:35                                                               ` Amir Goldstein
2021-02-28 22:25                                                                 ` Steve French
2021-03-01  6:18                                                                   ` Amir Goldstein
2021-03-01 14:41                                                       ` [RFC v3] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-03-01 14:58                                                         ` Amir Goldstein
2021-03-04  9:38                                                       ` [RFC v4] " Alejandro Colomar
2021-03-04 17:13                                                         ` Darrick J. Wong
2021-03-04 18:24                                                           ` Alejandro Colomar (man-pages)
2021-03-04 23:50                                                             ` Darrick J. Wong
2021-02-24  7:15                                     ` [PATCH v4] vfs: fix copy_file_range regression in cross-fs copies Amir Goldstein
2021-02-24  8:30                                       ` Petr Vorel
2021-02-18 20:41                             ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Steve French
2021-02-12 23:15       ` [PATCH 1/6] fs: Add flag to file_system_type to indicate content is generated Dave Chinner
2021-02-12  7:54   ` Amir Goldstein
2021-02-12  4:44 ` [PATCH 2/6] proc: Add FS_GENERATED_CONTENT to filesystem flags Nicolas Boichat
2021-02-12  4:44 ` [PATCH 6/6] vfs: Disallow copy_file_range on generated file systems Nicolas Boichat
2021-02-12  4:53   ` Darrick J. Wong
2021-02-12  4:59     ` Darrick J. Wong
2021-02-12  5:24       ` Nicolas Boichat
2021-02-14 23:09 ` [PATCH 0/6] Add generated flag to filesystem struct to block copy_file_range Al Viro

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