From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8CECF42A79F for ; Tue, 21 Jul 2026 07:41:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784619701; cv=none; b=VtynjGDZNELBb3Z82CiZL1XVABbGhlqsCvMHYqob0NajzdxEgn+sgPDyNxYpCOumFLEDQdaUBkZ5ADFrig5Up7hCMT4fYdiVYXQOgewswn+K/gsj4nvgIVXAN0ylkfvxexKtXaOwC+fFovf04khfr8vwYzs5g/OmiRyrR2FfA08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784619701; c=relaxed/simple; bh=7flbzxQM5NiSWaJSc4M+YFr1P8YHslMXW0JfW8C97jg=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=V52eKu2xqJ2d6VAxXqk4pfD024fl061yRD77K45pP/sDntyndH54Bi76ISCsIPdWmvXEZ0gZsnFWa+2lEn9x86/Ge0vspeOedBUOuQGOPorXFMNSYNLDaYJVvRDEu7R5lAONUgbQOGDH31pJbp6UT1hIBs3P3op9bV3E2ssmXyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OeQHhVhP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OeQHhVhP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 207C21F000E9; Tue, 21 Jul 2026 07:41:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784619700; bh=6RDa7GxGPcZxw1iR56r9UobJy+ITg20eg0gqvz46Dbg=; h=Date:Subject:From:To:Cc:References:In-Reply-To; b=OeQHhVhPSAjaAr6m2sK2/xPUH3iA6gDakIWCLn6DfD8uPGUuAAHHQES9SBQnCmgW9 kAMbhpLa+nJlipJ84DQQREh7ENV8cz02VRQOnOUWrNdaBkHOBxXtENoqS8Iw7H9YOC 5atWYHmSLpCeFKKEpDbLPo6HVvAlzS2I7W9Rp6kFwe2mF1VgDWJKZenpvYVeSxZLq0 syaofVJHX1MQpfRQvaIuuRS1HiXTKvIED9Jh3oFQ7ZKaDZoT2/MskaScLflm5UegVt nFX4UmAUw3R2VaJ7xEqgwtT6OyNwFJxuaMeG2T3XrWuSG1smdD83UPkKiD/oBoqadn PC0fhjjQuY/8Q== Message-ID: <234c56b7-4036-4d03-8d8d-6298d16c3a77@kernel.org> Date: Tue, 21 Jul 2026 09:41:36 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/slub: prevent pfmemalloc objects from entering the barn Content-Language: en-US From: "Vlastimil Babka (SUSE)" To: hu.shengming@zte.com.cn, harry@kernel.org, akpm@linux-foundation.org Cc: hao.li@linux.dev, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhang.run@zte.com.cn, cai.qu@zte.com.cn References: <20260721084522552ZPa16p1SRj3PYat3sqxuN@zte.com.cn> <01ea11f8-65b4-4941-adf7-423c3f000292@kernel.org> Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/21/26 09:34, Vlastimil Babka (SUSE) wrote: > On 7/21/26 02:45, hu.shengming@zte.com.cn wrote: >> From: Shengming Hu >> >> kmem_cache_return_sheaf() may refill a partially consumed sheaf before >> placing it in the barn. Without an explicit restriction, this refill may >> draw objects from pfmemalloc slabs and consume emergency reserves. >> >> Add __GFP_NOMEMALLOC so that returned sheaves are refilled only from >> non-pfmemalloc slabs. Also add __GFP_NOWARN, as suggested by Hao Li, >> because this refill is a best-effort attempt and failure is acceptable. >> If the refill fails, flush and free the sheaf instead. >> >> Fixes: 3c1ea5c5019f ("slab: sheaf prefilling for guaranteed allocations") > > Wonder if 1ce20c28eafd ("slab: handle pfmemalloc slabs properly with > sheaves") is a better match. Until that commit we just didn't care, and it > seems like this is a case that commit missed? Added to slab/for-next with changed Fixes: per above, but can adjust it further if it was wrong. Thanks! >> Cc: stable@vger.kernel.org >> Signed-off-by: Shengming Hu >> --- >> Changes in v3: >> - Replace “normal memory” with the more precise “non-pfmemalloc slabs”, >> and add Fixes: and Cc: stable@vger.kernel.org, as suggested by Harry. >> - Link to v2: https://lore.kernel.org/all/20260720211127124sYtTNbvsxCXN9_pDh-pwt@zte.com.cn/ >> >> Changes in v2: >> - Add __GFP_NOWARN as suggested by Hao. >> - Link to v1: https://lore.kernel.org/all/20260719113701797vZ3R8NxiqYt8dEfeUxtON@zte.com.cn/ >> >> --- >> mm/slub.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 53b4976d3831..357b7522c817 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -5123,7 +5123,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp, >> * simply flush and free it. >> */ >> if (!barn || data_race(barn->nr_full) >= MAX_FULL_SHEAVES || >> - refill_sheaf(s, sheaf, gfp)) { >> + refill_sheaf(s, sheaf, gfp | __GFP_NOMEMALLOC | __GFP_NOWARN)) { >> sheaf_flush_unused(s, sheaf); >> free_empty_sheaf(s, sheaf); >> return; >