Re:Re: [PATCH v3 3/3] exfat: drain in-flight DIO before buffered writes

["jiale yao" <19888972804@163.com>]

At 2026-10-03 09:17:18, "Chi Zhiling" <chizhiling@163.com> wrote:
>On 9/28/26 4:54 PM, Jiale Yao wrote:
>> An asynchronous direct write can remain in flight after the inode lock is
>> released.  If a buffered write dirties page cache while the direct write
>> is still pending, the direct write's post-I/O invalidation can find the
>> dirty pages, report a page cache invalidation failure, and record -EIO in
>> the mapping error sequence.  A later fsync() therefore returns -EIO.
>> 
>> Commit 15cdefd0c0522f9d5e12d947fa04f4c11649b699 ("ext4: drain
>> in-flight DIO before buffered write fallback") fixed the same race in
>> ext4.  ExFAT does not drain in-flight DIO before either a regular buffered
>> write or the buffered fallback after iomap_dio_rw() returns -ENOTBLK or a
>> short write.
>> 
>> Wait for in-flight DIO before calling iomap_file_buffered_write() in both
>> paths.
>> 
>> A reproducer using concurrent AIO direct writes and buffered fallback
>> triggered the following warning and made a subsequent fsync() return
>> -EIO:
>> 
>>    Page cache invalidation failure on direct I/O.  Possible data corruption
>>    due to collision with buffered I/O!
>> 
>> Fixes: 867b9c96dc83 ("exfat: add iomap direct I/O support")
>> Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@linux.alibaba.com
>> Signed-off-by: Jiale Yao <yaojiale02@163.com>
>> ---
>>   fs/exfat/file.c | 12 ++++++++++--
>>   1 file changed, 10 insertions(+), 2 deletions(-)
>> 
>> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
>> index a2a9ee1a2004..28811210663f 100644
>> --- a/fs/exfat/file.c
>> +++ b/fs/exfat/file.c
>> @@ -807,6 +807,8 @@ static ssize_t exfat_fallback_buffered_write(struct kiocb *iocb,
>>   
>>   	iocb->ki_flags &= ~IOCB_DIRECT;
>>   
>> +	inode_dio_wait(file_inode(iocb->ki_filp));
>> +
>>   	written = iomap_file_buffered_write(iocb, from, &exfat_write_iomap_ops,
>>   			NULL, NULL);
>>   	if (written < 0)
>> @@ -889,11 +891,17 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
>>   			goto unlock;
>>   	}
>>   
>> -	if (iocb->ki_flags & IOCB_DIRECT)
>> +	if (iocb->ki_flags & IOCB_DIRECT) {
>>   		ret = exfat_dio_write_iter(iocb, iter);
>> -	else
>> +	} else {
>> +		/*
>> +		 * Prevent concurrent direct I/O and buffered I/O to the same file
>> +		 * range. Wait for in-flight DIO to finish before dirtying pages.
>> +		 */
>> +		inode_dio_wait(inode);
>>   		ret = iomap_file_buffered_write(iocb, iter,
>>   				&exfat_write_iomap_ops, NULL, NULL);
>> +	}
>>   	if (ret < 0)
>>   		goto unlock;
>>   
>
>Also, if you don't mind, could you add inode_dio_wait() to 
>exfat_extend_valid_size() as well?
Sure, v4 in https://lore.kernel.org/all/20261003093035.532916-1-yaojiale02@163.com/
>
>Thanks.