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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 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; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: dazrpzamhmtzkk7w8ta84887jjwz4jy6 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0E93C140009 X-Rspam-User: X-HE-Tag: 1784621181-764080 X-HE-Meta: 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 Nly+2ZW4 dVtJ/r4XgHYQzGcFU2dSN4AbVD/oaQMPXTPe1PPlnZbjai8SamZlELS5QoZPRUYUiM5ICWrSTGubAcAAcgYYfiCAUY7+MLcLjyNdNr7ipWf17MKNZndpTbnFjedSQwUyFplXep2Udw20/MOwfDjgEAy6S08n6hEZ8w3uRupAq+aYxGx9oPBPyklwV0AxAHuFKkHDBx4a4HW7flEkVyaB8bQ4HFWm+fT4GMu271mjlBEp1YeJ5Pcpj4j8oX75lRX3jT2P2dp/xSKeVzOlLnBGmP4Ea3h5gdDLuWSITrsvB+TJJOlyeMTwvVa+XMQkUiKSvVYMgdt3/TTM7ngDdcS5HWPCPVYYOZlLywfwsckuMY97dAjmJ3/mct9h8ysOhxqqTVOssvKDtt04xQCo5FwE6IRO+NMowrqV9tWtfdqoEauyVY7c= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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;