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vfs: fix copy_file_range() averts filesystem freeze protection

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commit 10bc8e4af65946b727728d7479c028742321b60a upstream.

[backport comments for pre v5.15:
- ksmbd mentions are irrelevant - ksmbd hunks were dropped
- sb_write_started() is missing - assert was dropped
]

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")
Tested-by: Namjae Jeon <linkinjeon@kernel.org>
Tested-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Amir Goldstein
2022-12-13 15:13:41 +02:00
committed by Greg Kroah-Hartman
parent ed96733949
commit 965d93fb39
3 changed files with 23 additions and 6 deletions
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4
fs/nfsd/vfs.c
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@@ -584,8 +584,8 @@ ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
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);
ret = vfs_copy_file_range(src, src_pos, dst, dst_pos, count,
COPY_FILE_SPLICE);
return ret;
}