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From:   Namjae Jeon <linkinjeon@kernel.org>
Date:   Fri, 11 Nov 2022 23:53:08 +0900
Message-ID: <CAKYAXd--CCur4Pd9RhSTzV3ra7CV8zqsDgj-iOerun0sub1Xdw@mail.gmail.com>
Subject: Re: [PATCH] vfs: fix copy_file_range() averts filesystem freeze protection
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Olga Kornievskaia <olga.kornievskaia@gmail.com>,
        Luis Henriques <lhenriques@suse.com>,
        linux-fsdevel@vger.kernel.org, linux-cifs@vger.kernel.org,
        linux-nfs@vger.kernel.org
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2022-11-11 0:55 GMT+09:00, Amir Goldstein <amir73il@gmail.com>:
> Commit 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs
> copies") removed fallback to generic_copy_file_range() for cross-fs
> cases inside vfs_copy_file_range().
>
> To preserve behavior of nfsd and ksmbd server-side-copy, the fallback to
> generic_copy_file_range() was added in nfsd and ksmbd code, but that
> call is missing sb_start_write(), fsnotify hooks and more.
>
> Ideally, nfsd and ksmbd would pass a flag to vfs_copy_file_range() that
> will take care of the fallback, but that code would be subtle and we got
> vfs_copy_file_range() logic wrong too many times already.
>
> Instead, add a flag to explicitly request vfs_copy_file_range() to
> perform only generic_copy_file_range() and let nfsd and ksmbd use this
> flag only in the fallback path.
>
> This choise keeps the logic changes to minimum in the non-nfsd/ksmbd code
> paths to reduce the risk of further regressions.
>
> Fixes: 868f9f2f8e00 ("vfs: fix copy_file_range() regression in cross-fs
> copies")
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>
> Hi Al,
>
> Another fix for the long tradition of copy_file_range() regressions.
> This one only affected cross-fs server-side-copy from nfsd/ksmbd.
>
> I ran the copy_range fstests group on ext4/xfs/overlay to verify no
> regressions in local fs and nfsv3/nfsv4 to test server-side-copy.
>
> I also patched copy_file_range() to test the nfsd fallback code on
> local fs.
>
> Namje, could you please test ksmbd.
Works fine. You can add tested-by tag for ksmbd.
Tested-by: Namjae Jeon <linkinjeon@kernel.org>

>
> Thanks,
> Amir.