Re: [PATCH v1 0/5] exfat: fix valid_size handling and locking

[Chi Zhiling <chizhiling@163.com>]

On 10/3/26 7:42 AM, Namjae Jeon wrote:
> On Thu, Oct 1, 2026 at 11:53 AM Chi Zhiling <chizhiling@163.com> wrote:
>>
>> On 9/30/26 6:01 PM, Namjae Jeon wrote:
>>> On Sun, Sep 27, 2026 at 5:04 PM Chi Zhiling <chizhiling@163.com> wrote:
>>>>
>>>> From: Chi Zhiling <chizhiling@kylinos.cn>
>>>>
>>>> valid_size marks the on-disk up-to-date region of an exFAT file. It is
>>>> advanced from the write path, from read/zeroing completion, and via
>>>> truncate, while it is read without i_rwsem from ->iomap_begin and from bio
>>>> completion context. This series fixes several races and stale-data windows
>>>> that follow from that split ownership.
>>>>
>>>> Patches 1-2 are self-contained fixes: an append write may be moved to EOF
>>>> by generic_write_checks(), so valid_size must be advanced using the
>>>> recalculated position; and exfat_zero_new_range() must mark non-uptodate
>>>> pages dirty so the whole page is written back.
>>>>
>>>> Patches 3-4 are prerequisites for patch 5: truncate now holds the
>>>> invalidate lock so it is mutually exclusive with mmap writes, and
>>>> valid_size/zeroed_size become atomic so they can be read safely outside
>>>> i_rwsem. Patch 5 then takes exfat_page_mkwrite() out from under i_rwsem,
>>>> since blocking on the inode lock under mmap_lock could deadlock and its
>>>> VM_FAULT_RETRY result is not honored, and advances valid_size under the
>>>> folio lock to keep the page cache and valid_size consistent.
>>>>
>>>> Link: https://lore.kernel.org/exfat/10029d6f-13cc-4d17-a2f9-b093a8339dde@163.com/T/#t
>>>>
>>>> Chi Zhiling (5):
>>>>     exfat: advance valid_size to EOF for append writes
>>>>     exfat: dirty all new pages when extending valid_size
>>>>     exfat: hold the invalidate lock while truncating
>>>>     exfat: make valid_size and zeroed_size atomic
>>>>     exfat: use folio lock to protect valid_size
>>> Could you check the review comments from Sashiko ?
>>>
>>> https://sashiko.dev/#/patchset/20260927080305.831641-1-chizhiling%40163.com
>>
>> Okay, I’ll take a close look at this review comment.
>>
>> I also noticed that the comment mentions that concurrent DIO and page
>> faults may lead to data corruption. I believe this is a long-standing
>> issue, and I don’t currently have a good way to fix it.
> Okay, I'll take a look at that. Will you send v2 patchset soon?
> Thanks!

Okay