Re: [PATCH v4 01/11] iomap: introduce IOMAP_F_ZERO_TAIL flag

[Christian Brauner]

On Mon, May 18, 2026 at 08:46:55PM +0900, Namjae Jeon wrote:
> In filesystems that maintain a separate Valid Data Length, such as exFAT
> and NTFS, a partial write may start at or beyond the current valid_size and
> extend it. In this case, the region after the previous valid_size but
> within the same filesystem block is considered unwritten.
> 
> This patch introduces IOMAP_F_ZERO_TAIL. When this flag is set in iomap,
> __iomap_write_begin() will zero only the tail portion while preserving any
> valid data before it in the same block.
> 
> Without this tail zeroing, stale data in the unwritten portion of the block
> can remain in the page cache. Subsequent reads can then return incorrect
> contents from that region.
> 
> Acked-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
> ---

I've applied this. The branch is marked as shared with the exfat tree
and will remain stable.