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Subject: Re: [PATCH v2] vfs: generic_copy_file_checks should return EINVAL
 when source offset is beyond EOF
From:   dai.ngo@oracle.com
To:     "Darrick J. Wong" <djwong@kernel.org>
Cc:     linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org
References: <20210201204952.74625-1-dai.ngo@oracle.com>
 <20210201211446.GA7187@magnolia>
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Hi Darrick,

My man page was out-of-date. The latest man page of coy_file_range is more clear:

This EINVAL was removed:

        EINVAL Requested range extends beyond the end of the source file; or the flags argument is not 0.

and replaced with this:
         
*EINVAL *The/flags/  argument is not 0

Thanks,
-Dai

On 2/1/21 1:51 PM, dai.ngo@oracle.com wrote:
>
> On 2/1/21 1:14 PM, Darrick J. Wong wrote:
>> On Mon, Feb 01, 2021 at 03:49:52PM -0500, Dai Ngo wrote:
>>> Fix by returning -EINVAL instead of 0, per man page of copy_file_range,
>> Huh?  That's not what the manpage[1] says:
>>
>> RETURN VALUE
>>         Upon successful completion, copy_file_range() will return the
>> number of bytes copied between files.  This could be less than the
>> length originally requested.  If the file offset of fd_in is at or past
>> the end of file, no bytes are copied, and copy_file_range() returns
>> zero.
>
> In the ERROR section:
>
> ERROR
>     EINVAL Requested range extends beyond the end of the source file; 
> or the flags argument is not 0.
>
> -Dai
>
>>
>> --D
>>
>> [1] 
>> https://urldefense.com/v3/__https://man7.org/linux/man-pages/man2/copy_file_range.2.html*RETURN_VALUE__;Iw!!GqivPVa7Brio!N8XGLyK9dUTWOYWmb3NCuq-9kL-tX8OGcq-sV7M53ub5KMgr7e93a2B8eUryKw$
>>
>>> when the requested range extends beyond the end of the source file.
>>> Problem was discovered by subtest inter11 of nfstest_ssc.
>>>
>>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>>> ---
>>>   fs/read_write.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/fs/read_write.c b/fs/read_write.c
>>> index 75f764b43418..438c00910716 100644
>>> --- a/fs/read_write.c
>>> +++ b/fs/read_write.c
>>> @@ -1445,7 +1445,7 @@ static int generic_copy_file_checks(struct 
>>> file *file_in, loff_t pos_in,
>>>       /* Shorten the copy to EOF */
>>>       size_in = i_size_read(inode_in);
>>>       if (pos_in >= size_in)
>>> -        count = 0;
>>> +        count = -EINVAL;
>>>       else
>>>           count = min(count, size_in - (uint64_t)pos_in);
>>>   --
>>> 2.9.5
>>>