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 8DFBC43744D for ; Tue, 21 Jul 2026 08:06:21 +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=1784621182; cv=none; b=sV7sjdJpWNCw6wFvnah5sfLpaEuz2DLMzI6aK0/qBYyL+PMlShOLa61IezAHxlFbtLdoL89/n7rb7BdYpqp7EkAx4U9vg2ZnxFQMBl1r7drjZWskLDG0o3MkNnFOoZupMmpJ99uM1ayu1IIneLKkYSBtkVsFTLCSQthpMpqefXw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784621182; c=relaxed/simple; bh=ParVS40ylTkyfnxPMqbv606hTT6bDi7QQc05n8PYyAw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=X7vAPTMW+ZcLe9u1KBJHDPWnWsilyiwV5j7io/n3nDmsOQy5a+lxbOqONCF1bNXGYucuwyCGkkGGI29YOPsgevtBZvvQoE/1YuNp3RsouR4rvE61Hotaqys1lwMAynz90XISCbynRP0+dH8OhZ8lg0hAAtkLZl7S8htdUcGilvc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YiSd8pDU; 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="YiSd8pDU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A8711F00A3A; Tue, 21 Jul 2026 08:06:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784621181; bh=ROLOrfPqMTfQb393OeJq2htXFD07Htbn862T+F3MXnE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=YiSd8pDUlnk54p+cGidnrLlHwhi5yZ2AVjrgGHvwLxttGbMXx+XqXN8synT9inFmJ cIT4D3U6E76mBReMbCCip8dEZDv8f85y5wye92oxssvHvJS2q1X33CsKweQ24BX7y0 6yEyfP6/h9WEo/imefAHtTQqczYlqlgCsTB/8NIpAmRw9XWmBwkGaG3BSzSrwYhAhv Dkzjr42zd5yQ4LqGe6UHz1Gg7WNacsg3JIdbbt0FCS0w5UZhQu7ZDEr42JFY5aKxON y6orMEYgD3vOBeQLTLGlzzHZVheUtrIxkNtNo5NaoDrWtXB/wr6BRyJVnae1ABeWlG ULhQ3r7gkednw== Message-ID: <17fe32e3-6761-4101-9d5f-2b22c8a83d7b@kernel.org> Date: Tue, 21 Jul 2026 10:06:17 +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 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> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260721084522552ZPa16p1SRj3PYat3sqxuN@zte.com.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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") > Cc: stable@vger.kernel.org > Signed-off-by: Shengming Hu Ah so per sashiko [1] we should consider adding also a __GFP_NORETRY to avoid an OOM kill. Seems reasonable that an API for returning memory should not cause an OOM kill... it's unusual enough that it takes gfp flags but I thought defaulting to GFP_NOWAIT would be an unnecessary limitation. I can add __GFP_NORETRY locally if others agree. [1] https://sashiko.dev/#/patchset/20260721084522552ZPa16p1SRj3PYat3sqxuN%40zte.com.cn > --- > 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;