linux-kernel - Re: [PATCH v3 1/3] mm/gup: fix wrongly calculated returned value in fault_in_safe

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Message-ID: <Z_TvDwA6xGfXMiED@localhost.localdomain>
Date: Tue, 8 Apr 2025 11:40:31 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Baoquan He <bhe@...hat.com>
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org, david@...hat.com,
	mingo@...nel.org, yanjun.zhu@...ux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] mm/gup: fix wrongly calculated returned value in
 fault_in_safe_writeable()

On Mon, Apr 07, 2025 at 11:03:04AM +0800, Baoquan He wrote:
> Not like fault_in_readable() or fault_in_writeable(), in
> fault_in_safe_writeable() local variable 'start' is increased page
> by page to loop till the whole address range is handled. However,
> it mistakenly calcalates the size of handled range with 'uaddr - start'.
                ^^ calculates
> 
> Here fix the code bug in fault_in_safe_writeable(), and also adjusting
> the codes in fault_in_readable() and fault_in_writeable() to use local
> variable 'start' to loop so that codes in these three functions are
> consistent.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>

The fix for the bug in fault_in_safe_writeable() looks good to me.
But I think that David suggested the other way around wrt. uaddr and
start variables in those three functions? I think he had in mind that
fault_in_safe_writeable() follows fault_in_safe_writeable() and
fault_in_readable() lead.

Other than that looks good to me.


-- 
Oscar Salvador
SUSE Labs