linux-kernel - Re: [PATCH] mm: Fix a race during split THP

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Date:   Sat, 10 Oct 2020 08:26:26 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Rafael Aquini <aquini@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH] mm: Fix a race during split THP

Matthew Wilcox <willy@...radead.org> writes:

> On Fri, Oct 09, 2020 at 03:36:47PM +0800, Huang, Ying wrote:
>> +	if (PageSwapCache(head)) {
>> +		swp_entry_t entry = { .val = page_private(head) };
>> +
>> +		split_swap_cluster(entry);
>> +	}
> ...
>> -		if (PageSwapCache(head)) {
>> -			swp_entry_t entry = { .val = page_private(head) };
>> -
>> -			ret = split_swap_cluster(entry);
>
> Are we sure split_swap_cluster() can't fail?  Or if it does fail, it's
> OK to continue with the split and not report the error?

split_swap_cluster() can only fail for invalid swap entry.  Which isn't
expected to happen in this situation.

Best Regards,
Huang, Ying