Re: [PATCH] f2fs: only redirty pinned folios in redirty_blocks

[Chao Yu <chao@kernel.org>]

On 7/27/26 21:04, Wenjie Qi wrote:
> redirty_blocks() pins folios with read_cache_folio() and then walks the
> same range again with filemap_lock_folio() to redirty them and drop the
> references it took.
> 
> Commit 5951fee46bef ("f2fs: Use a folio in redirty_blocks()") changed
> the second pass to a do/while loop. If read_cache_folio() fails before
> anything is pinned, page_idx does not advance but the cleanup loop still
> runs once.
> 
> If readahead has already populated the failed folio in page cache, that
> extra iteration finds it and folio_put_refs(folio, 2) drops one
> reference too many. Later drop_caches or reclaim can then report
> "BUG: Bad page state".
> 
> Only redirty the range that was pinned successfully.
> 
> Fixes: 5951fee46bef ("f2fs: Use a folio in redirty_blocks()")
> Cc: stable@kernel.org
> Assisted-by: Codex:gpt-5.5
> Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,