linux-kernel - Re: [PATCH 1/6] fuse: drop usage of folio

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Message-ID: <aA7N1SHoR-tY4PJW@casper.infradead.org>
Date: Mon, 28 Apr 2025 01:37:42 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, Chris Li <chrisl@...nel.org>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	"Huang, Ying" <ying.huang@...ux.alibaba.com>,
	Nhat Pham <nphamcs@...il.com>, Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
	Joanne Koong <joannelkoong@...il.com>,
	Josef Bacik <josef@...icpanda.com>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/6] fuse: drop usage of folio_index

On Mon, Apr 28, 2025 at 02:59:03AM +0800, Kairui Song wrote:
> folio_index is only needed for mixed usage of page cache and swap
> cache, for pure page cache usage, the caller can just use
> folio->index instead.
> 
> It can't be a swap cache folio here.  Swap mapping may only call into fs
> through `swap_rw` and that is not supported for fuse.  So just drop it
> and use folio->index instead.
> 
> uigned-off-by: Kairui Song <kasong@...cent.com>
> Cc: Miklos Szeredi <miklos@...redi.hu>
> Cc: Joanne Koong <joannelkoong@...il.com>
> Cc: Josef Bacik <josef@...icpanda.com>
> Cc: linux-fsdevel@...r.kernel.org
> Signed-off-by: Kairui Song <kasong@...cent.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>

> @@ -2349,7 +2349,7 @@ static bool fuse_writepage_need_send(struct fuse_conn *fc, struct folio *folio,
>  		return true;
>  
>  	/* Discontinuity */
> -	if (data->orig_folios[ap->num_folios - 1]->index + 1 != folio_index(folio))
> +	if (data->orig_folios[ap->num_folios - 1]->index + 1 != folio->index)
>  		return true;

This looks like a pre-existing bug.

-	if (data->orig_folios[ap->num_folios - 1]->index + 1 != folio_index(folio))
+	prev_folio = data->orig_folios[ap->num_folios - 1];
+	if (prev_folio->index + folio_nr_pages(prev_folio) != folio->index)
		return true;