linux-kernel - Re: [PATCH] iomap: move prefaulting out of hot write path

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Message-ID: <aIaj69N19WCbKKy8@casper.infradead.org>
Date: Sun, 27 Jul 2025 23:10:51 +0100
From: Matthew Wilcox <willy@...radead.org>
To: alexjlzheng@...il.com
Cc: brauner@...nel.org, djwong@...nel.org, dave.hansen@...ux.intel.com,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jinliang Zheng <alexjlzheng@...cent.com>
Subject: Re: [PATCH] iomap: move prefaulting out of hot write path

On Sat, Jul 26, 2025 at 05:09:56PM +0800, alexjlzheng@...il.com wrote:
> @@ -992,6 +977,12 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  		if (mapping_writably_mapped(mapping))
>  			flush_dcache_folio(folio);
>  
> +		/*
> +		 * copy_folio_from_iter_atomic() short-circuits page fault handle
> +		 * logics via pagefault_disable(), to prevent deadlock scenarios
> +		 * when both source and destination buffers reside within the same
> +		 * folio (mmap, ...).
> +		 */

Why did you change this comment from the one in 665575cff098?
The comment in that commit is correct.  This comment is so badly
mangled, it isn't even wrong.