From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D748C2DCF70 for ; Thu, 6 Nov 2025 07:23:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762413830; cv=none; b=UW3Gtv27TGoTdSIge9WdXveOD7U3CS4dZ6WdfrXbbIONkE8oOAldhWILmeED7R8cBCIhz/EQsYFqhGH62n8iV+pyKlkcmpCEF8JfhES9qYbyi9wp+eRxgZve2amV53nnGwuIokigANbuA/GTqSqRvjrC4yO9pYnWclIoo1Ds6yQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762413830; c=relaxed/simple; bh=PpCYZiESS+NYFao5qNfGpf2j/tTFJn3MrA5HeQxrUNk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Jkl/scQJzWHsItgCgycXYMZeSMx93X+XnLHJ3VcwmdThBLrxQe/BOOS7ZXpdIPTq8sadc97BV6MXmbVCFZMPOUyzTS7hVyJAlEBUWXIsWFkJ4SrfYj8hdHf874ey3G9c2xHP3aOFJXAd/MvIi+QmKUJe7bz33IHWtwgVY36UCZQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=1ru3bnl6; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=BsryQK1I; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=hkkosBGu; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=B0kfOKCP; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="1ru3bnl6"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="BsryQK1I"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="hkkosBGu"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="B0kfOKCP" Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id D7F59211C4; Thu, 6 Nov 2025 07:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1762413826; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=7KuTnD+Lrz4fdyLGJ4uF39ab38gWiaLaVToVQMrbw5E=; b=1ru3bnl6zTaJQ22XU2gMsGWTpkp+gmHjZZ2t57pZnLSE0QjP0E4B1zcCm8TnUwYyfhG/ep OpbTc6WwNFKkMjtP4c8sXl6Ym+xAaFBERP40zXBQU74CT247gS/19DU9MnjP+otQHreMVI vs/S4A7gDgq3TAGLaO4pVQsRsSPNGmQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1762413826; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=7KuTnD+Lrz4fdyLGJ4uF39ab38gWiaLaVToVQMrbw5E=; b=BsryQK1I2wVpamBuHrtZ31BKHFAtMHf9K/Tl5yuw8v+MxsMLHcCbufG/28Lw2pHrIHXDzD PfSNFhbLG5sCPrAw== Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=hkkosBGu; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=B0kfOKCP DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1762413825; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=7KuTnD+Lrz4fdyLGJ4uF39ab38gWiaLaVToVQMrbw5E=; b=hkkosBGuczAqLSXJr+/wi6QitrxxQFm0+AGDbamyv1Hy6AxZBklElEY7Ezgt4Bnt4z7fyQ qfBeJRVDWzYhbvr4amFFMTne3KNKcgx/e35xjXNT7ApSqUpDfqFPGM7/uSklQc27gFJD6Y yfvk/tclGtIKrrMi5bXpX6Z0o90D4hg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1762413825; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=7KuTnD+Lrz4fdyLGJ4uF39ab38gWiaLaVToVQMrbw5E=; b=B0kfOKCPU7tEewGxnfh3t5a/1LSwMFkJ2xB7BBlodeWGgw+J1Dj5HeNkwMa/qS9L6oRqlV QFQkN5b/C9x5+NDg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id B68C9139A9; Thu, 6 Nov 2025 07:23:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id AZ9yKwFNDGk8GAAAD6G6ig (envelope-from ); Thu, 06 Nov 2025 07:23:45 +0000 Message-ID: <2d4356a4-a0c1-423a-bd40-af1f8a28fd84@suse.cz> Date: Thu, 6 Nov 2025 08:23:45 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] slab: move kfence_alloc() out of internal bulk alloc To: Alexei Starovoitov Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , "Liam R. Howlett" , Suren Baghdasaryan , Alexei Starovoitov , linux-mm , LKML , bpf , kasan-dev , Alexander Potapenko , Marco Elver , Dmitry Vyukov References: <20251105-sheaves-cleanups-v1-0-b8218e1ac7ef@suse.cz> <20251105-sheaves-cleanups-v1-2-b8218e1ac7ef@suse.cz> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D7F59211C4 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_DN_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_TO(0.00)[gmail.com]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; MID_RHS_MATCH_FROM(0.00)[]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.cz:email,suse.cz:mid,suse.cz:dkim] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -3.01 X-Spam-Level: On 11/6/25 03:39, Alexei Starovoitov wrote: > On Wed, Nov 5, 2025 at 1:05 AM Vlastimil Babka wrote: >> >> SLUB's internal bulk allocation __kmem_cache_alloc_bulk() can currently >> allocate some objects from KFENCE, i.e. when refilling a sheaf. It works >> but it's conceptually the wrong layer, as KFENCE allocations should only >> happen when objects are actually handed out from slab to its users. >> >> Currently for sheaf-enabled caches, slab_alloc_node() can return KFENCE >> object via kfence_alloc(), but also via alloc_from_pcs() when a sheaf >> was refilled with KFENCE objects. Continuing like this would also >> complicate the upcoming sheaf refill changes. >> >> Thus remove KFENCE allocation from __kmem_cache_alloc_bulk() and move it >> to the places that return slab objects to users. slab_alloc_node() is >> already covered (see above). Add kfence_alloc() to >> kmem_cache_alloc_from_sheaf() to handle KFENCE allocations from >> prefilled sheafs, with a comment that the caller should not expect the >> sheaf size to decrease after every allocation because of this >> possibility. >> >> For kmem_cache_alloc_bulk() implement a different strategy to handle >> KFENCE upfront and rely on internal batched operations afterwards. >> Assume there will be at most once KFENCE allocation per bulk allocation >> and then assign its index in the array of objects randomly. >> >> Cc: Alexander Potapenko >> Cc: Marco Elver >> Cc: Dmitry Vyukov >> Signed-off-by: Vlastimil Babka >> --- >> mm/slub.c | 44 ++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 36 insertions(+), 8 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 074abe8e79f8..0237a329d4e5 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -5540,6 +5540,9 @@ int kmem_cache_refill_sheaf(struct kmem_cache *s, gfp_t gfp, >> * >> * The gfp parameter is meant only to specify __GFP_ZERO or __GFP_ACCOUNT >> * memcg charging is forced over limit if necessary, to avoid failure. >> + * >> + * It is possible that the allocation comes from kfence and then the sheaf >> + * size is not decreased. >> */ >> void * >> kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp, >> @@ -5551,7 +5554,10 @@ kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp, >> if (sheaf->size == 0) >> goto out; >> >> - ret = sheaf->objects[--sheaf->size]; >> + ret = kfence_alloc(s, s->object_size, gfp); >> + >> + if (likely(!ret)) >> + ret = sheaf->objects[--sheaf->size]; > > Judging by this direction you plan to add it to kmalloc/alloc_from_pcs too? No, kmem_cache_alloc_from_sheaf() is a new API for use cases like maple tree, it's different from the internal alloc_from_pcs() caching. > If so it will break sheaves+kmalloc_nolock approach in > your prior patch set, since kfence_alloc() is not trylock-ed. > Or this will stay kmem_cache specific? I rechecked the result of the full RFC and kfence_alloc() didn't appear in kmalloc_nolock() path. I would say this patch moved it rather in the opposite direction, away from internal layers that could end up in kmalloc_nolock() path when kmalloc caches have sheaves.