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b=gn5uZuhUpXzP9VigOESWPHGxXoZ5RZinv++4S35D7dxPQwaPB2DJAqvIz7cSnT7GA 4LgPXNxYrhRNw6829RNDPTllKQz+pCYGK3D4bqmtJWqNNobD+XSRmS2GT8nVB/fQJ+ SpPBFKeIKyfbfHSzTASJp1DxuRpYyp9Ln0XQh5cafRg9/SO7i2bLMSAPOPXuuGVDS7 2yj5q9Qamzuhz9BgwLuE90A9knKqMBMtwxivdKcqW0DP8RyAvaRIWJHzKm/4aMFewh 4kGyEqwghU9lKYEYw3ZYtRMgwHrAs+YoxZg2bfGxDGEKmiP3ZEjmmm7nOsQZPza84F siW62n/ym6rSA== Message-ID: <01ea11f8-65b4-4941-adf7-423c3f000292@kernel.org> Date: Tue, 21 Jul 2026 09:34:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/slub: prevent pfmemalloc objects from entering the barn 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)" Content-Language: en-US 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 X-Stat-Signature: 3ozx589tmsbuq93wx67xrsjtykfbo8di X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A4475180002 X-HE-Tag: 1784619246-325334 X-HE-Meta: U2FsdGVkX18VNL1inbKY/umPJg2rkLvLRBBKbNTbOYVsZ3RzgA77yy0jEQ2dGYWut58DIc901Q0X/qVh4LuNR2TLeUUb1LDQ0gN8HcfBmUupiYIEVp/jUXX1nM0t2nxZdSmBObWbtUPsi+s5mpEsNPGeemqjlpANcoiXOGEPEkwpzZrK9q/MhibNcKKbsk+5KbMoE4pTcpZC9XdPVpE4F/8GTvQqfsfjOW+nuPhMeSE/eDLs3Grxj633A4mSi9GPPls+J0Hzrzd5BE1rRJtD49fUhChHmDKGTSb8/0+SLZEBvjz93/teaZE85DsnmnRVe+acVU1nw8eCXItEeH69QtJqKK7CUqs3HTnpN26cw8cfn0A+WN0COhrv2FPcY/XwILeoUfHBRqkPKRtWi2TCG3RSCX1LKvOWFqlRuKGT9EjOoj78OGIWkj4XCHzQpvaR9Hqf09gYUBWObSODie4tkH8hyCyPIpm7mkhnzbpHLvCOYYePlSs8fb5VTbo2iLCM7ISJNWa1werrQYd5W3kiEyayWG6rvK2yy+QFvkhkYmhZK394qH2Fw5PkUkX8TGDIq8XI+QJVhNQ/HdgCGxIEbmutaWKCdGnEfRaM/C3472J25vO4qdjCay9J4/wnMulhodbz52CYzH/0S9Vf83cfCk2seVuv8yfu8nSXpBu7kWz0AwLXIuEQJ59t99LQDa3vIu2fn7fDNiPyv/YSh6ZW4ltKORM3rH8BVZQ1RlP4FGGyPb1w35oCq8hfIYwRA1AF43No6m/1cyihYsrHgijTp234INWKog757mvDTDwzDzDeC88bKs3jHY2/gOn+McUKLPve60qCQFx6/7iL8Ujs+gLw5sOxwkK2soEGANtYillN2dsbj/9jX52U/kxG3nX0tOI9YDmWmdS7LFU7SXnziVFCo35sX2jnAjP1399hD3nAA43Gkw7vKRaTYfPAH5cVy6vyflxB38un5/x0khF uWDfPH8S aI/0snLQhnz3B3eLP3p7sqKsqpu0Rj3XhwkSW7OdyPrEU3FIpJFe7NyPa7ZCcxCrn1TBC8QlboWCNrXyNzTGjs+gzdtOKMZu726R11vISyvHJBdGNnXuj468oWpN2EO8m/UCh43ChF6/v7XWgJXajz0RErrRaF3Uz9ozaFIL73kLeQPU7Ls5wUsJAttReBgfMe155ARdw7hU39gzuTjpiHwlX8QiBqBJaHsHBVs9XB21F2qcaqmbbIFK/N/a2Gj7n2ZJsKRMAsxFhjrxSy21zZUv5Fox3nue4A+m4TT5WeQX5mHd9y0uumGHP18+fk1ZjQ9FZRi4gMP/Dk5/H8V7GU8t+3JasbF0RvS5GjgJDGuA/VVU= 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") 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? > 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;