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

[Namjae Jeon]

On Sun, Sep 27, 2026 at 5:04 PM Chi Zhiling <chizhiling@xxxxxxx> wrote:
>
> From: Chi Zhiling <chizhiling@xxxxxxxxxx>
>
> 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@xxxxxxx/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

Thanks!