From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91231CCD1AB for ; Fri, 24 Oct 2025 09:39:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F2E008E006E; Fri, 24 Oct 2025 05:39:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F052E8E0042; Fri, 24 Oct 2025 05:39:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DCD2A8E006E; Fri, 24 Oct 2025 05:39:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id CC6CA8E0042 for ; Fri, 24 Oct 2025 05:39:56 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 639611A0E03 for ; Fri, 24 Oct 2025 09:39:56 +0000 (UTC) X-FDA: 84032511192.11.161CE76 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf02.hostedemail.com (Postfix) with ESMTP id CF11E80002 for ; Fri, 24 Oct 2025 09:39:53 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=RrzCA3KC; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=3xkpbhDy; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=mRm1e6Qt; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=3OOr9Fx0; spf=pass (imf02.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761298794; a=rsa-sha256; cv=none; b=Wi/w/F1+uyE4aioDwBpGiFBPlN9vbxj3k/PZwoC1iR2QjURfQTC7qR25Bjm9AmNH6uJq2/ eFLzwcSek2fKJfspUXKUh5+X6PBgYVUYkL8kwBoEbcgiR9H41aqdLl3+4RCIT+N5rA0ysb w7o7wja85eR0vqtJyqUKsjD2Y460tfc= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=RrzCA3KC; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=3xkpbhDy; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=mRm1e6Qt; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=3OOr9Fx0; spf=pass (imf02.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761298794; h=from:from:sender:reply-to:subject:subject: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:dkim-signature; bh=HaeU5LbPknUgXKPUkJQnm2Eei92xzLJh6du52BkuqtA=; b=ZLUTORKyfwNH7LOzDhxaQW3KS586s5posZI+as2wJh+NnNykCuQwxioc/06hv4gttuWpZd pE3FeD2VGSB9IORPkOEEfB34cYpZbEVUJ5Op/bQNtq21kp+kXWnSN8rVV9NPynzRAEvRGy ADPnzRjxibQ4muBSZtQxgMyI0FkpYzw= 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 277E521208; Fri, 24 Oct 2025 09:39:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1761298788; 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=HaeU5LbPknUgXKPUkJQnm2Eei92xzLJh6du52BkuqtA=; b=RrzCA3KCRESdRNCEsTw5XqDS0TnaN7YW6KgYWy/NZ4ql7+WHEPhzf6lK3lo9VfXGhQl7Ct sqMHRWch8Ho6W5reGwlom8aY03JRMjFN102NCTcBMT4ZFFqL9tHvDkJHqHdaReKdQgS+ne dp2JItXqSv4vFqRyvyAmGM75QBDFtJw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1761298788; 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=HaeU5LbPknUgXKPUkJQnm2Eei92xzLJh6du52BkuqtA=; b=3xkpbhDy2G0quZ8iCxYPCL22vW1lCUfs3Fzh8h1xV5XORy0YeFxUzJ2ZPM/Y96jbRBrd6Q 4HKmEUgeLg+bvrAA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1761298784; 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=HaeU5LbPknUgXKPUkJQnm2Eei92xzLJh6du52BkuqtA=; b=mRm1e6QtA7ifuVnhcBcm22FOsKGeWC4VhNWn1dIoJAavxc9ViIz9pHaCVYAnuv8J077jGl LmkRmW4OSii079a/+XERAHDYbUTaZYSKgkplJ9OMJ80iFDvzy6u2y53NZQkXihpHEOEYMZ phhzTn8CB1VERSzNSe4bNpN0aP9Zlog= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1761298784; 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=HaeU5LbPknUgXKPUkJQnm2Eei92xzLJh6du52BkuqtA=; b=3OOr9Fx05gyUFr0wK3a4n2/BU0ArJP3tzJF828bttoQ+ByfNCrMTDTicvRuqaUZJb0Akte 302zmNe8OQmnr6Ag== 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 1160F132C2; Fri, 24 Oct 2025 09:39:44 +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 3VjjA2BJ+2g0HwAAD6G6ig (envelope-from ); Fri, 24 Oct 2025 09:39:44 +0000 Message-ID: <8b152d73-ecc4-415c-acdc-3f5105412ac0@suse.cz> Date: Fri, 24 Oct 2025 11:39:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] slab: Fix obj_ext is mistakenly considered NULL due to race condition Content-Language: en-US To: Hao Ge , Harry Yoo Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Suren Baghdasaryan , Shakeel Butt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge References: <20251023143313.1327968-1-hao.ge@linux.dev> <49a186cf-c248-45ff-a61c-a6de1a3a98b7@linux.dev> 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: <49a186cf-c248-45ff-a61c-a6de1a3a98b7@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Stat-Signature: mh74e9wcoyokwwz851i3rhfsdtmwouyh X-Rspamd-Queue-Id: CF11E80002 X-Rspamd-Server: rspam09 X-HE-Tag: 1761298793-317836 X-HE-Meta: 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 dYQs34X2 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/24/25 11:27, Hao Ge wrote: > Hi Harry > Hi Vlastimil > > > Thank you for adding V2 to your tree. Now, should I resubmit V3, > > or can you assist with making these modifications in your tree? Massaged it a bit more and now have this: commit b4bdf6770cadb8bffcf3dce7ad7a346979f79ede Author: Hao Ge Date: Thu Oct 23 22:33:13 2025 +0800 slab: Fix obj_ext mistakenly considered NULL due to race condition If two competing threads enter alloc_slab_obj_exts(), and the one that allocates the vector wins the cmpxchg(), the other thread that failed allocation mistakenly assumes that slab->obj_exts is still empty due to its own allocation failure. This will then trigger warnings with CONFIG_MEM_ALLOC_PROFILING_DEBUG checks in the subsequent free path. Therefore, let's check the result of cmpxchg() to see if marking the allocation as failed was successful. If it wasn't, check whether the winning side has succeeded its allocation (it might have been also marking it as failed) and if yes, return success. Suggested-by: Harry Yoo Signed-off-by: Hao Ge Link: https://patch.msgid.link/20251023143313.1327968-1-hao.ge@linux.dev Reviewed-by: Suren Baghdasaryan Reviewed-by: Harry Yoo Signed-off-by: Vlastimil Babka diff --git a/mm/slub.c b/mm/slub.c index 87a1d2f9de0d..d4367f25b20d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2052,9 +2052,9 @@ static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) } } -static inline void mark_failed_objexts_alloc(struct slab *slab) +static inline bool mark_failed_objexts_alloc(struct slab *slab) { - cmpxchg(&slab->obj_exts, 0, OBJEXTS_ALLOC_FAIL); + return cmpxchg(&slab->obj_exts, 0, OBJEXTS_ALLOC_FAIL) == 0; } static inline void handle_failed_objexts_alloc(unsigned long obj_exts, @@ -2076,7 +2076,7 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts, #else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */ static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) {} -static inline void mark_failed_objexts_alloc(struct slab *slab) {} +static inline bool mark_failed_objexts_alloc(struct slab *slab) { return false; } static inline void handle_failed_objexts_alloc(unsigned long obj_exts, struct slabobj_ext *vec, unsigned int objects) {} @@ -2124,8 +2124,14 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, slab_nid(slab)); } if (!vec) { - /* Mark vectors which failed to allocate */ - mark_failed_objexts_alloc(slab); + /* + * Try to mark vectors which failed to allocate. + * If this operation fails, there may be a racing process + * that has already completed the allocation. + */ + if (!mark_failed_objexts_alloc(slab) && + slab_obj_exts(slab)) + return 0; return -ENOMEM; }