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 849A1D74EEC for ; Fri, 23 Jan 2026 16:21:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AAECC6B050D; Fri, 23 Jan 2026 11:21:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A7BBD6B050E; Fri, 23 Jan 2026 11:21:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 966B86B050F; Fri, 23 Jan 2026 11:21:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 846686B050D for ; Fri, 23 Jan 2026 11:21:32 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 20B9A140401 for ; Fri, 23 Jan 2026 16:21:32 +0000 (UTC) X-FDA: 84363744024.05.69EDA48 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) by imf02.hostedemail.com (Postfix) with ESMTP id 8C91C80015 for ; Fri, 23 Jan 2026 16:21:28 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=kiL0wXJJ; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=WYSEuCkZ; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=kiL0wXJJ; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=WYSEuCkZ; spf=pass (imf02.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 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=1769185289; 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=L58AJIr91oTMKf0PXTG1TbeTEeGFV9i4xfX9fFVLhOQ=; b=CUxjD5m2liXbbEAnW60MaQeXLMipRBpoBUX+afPQEaO1zU96vOFkJ8AL+PxUL4Q6legoqv U6Gr4H5BPkikhyMjsXfafZtDniQW8jxvmgW4GUbfcmtbOVhywLr3DxPSeNmE++L9eNHNAn 8TqDbtUURDQjyc8wShsum/KALICSH58= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=kiL0wXJJ; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=WYSEuCkZ; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=kiL0wXJJ; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=WYSEuCkZ; spf=pass (imf02.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769185289; a=rsa-sha256; cv=none; b=Yx0aGQtv4EaEWPujToUSjdK+mLzT1Ym4w3F5gj5LdOUBjgvVb6FdZUBZsvUM/GFmMRlcXa 1xVdcHgdu7mz5Sd3t9dUVzXZ/23SQggs9gMA5MqNNzisSaK1Bk1v1f2QLixHA5NL4xsC88 8F5bpKWhaTabp+hoZ2unCXGyEH5d7ag= 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-out2.suse.de (Postfix) with ESMTPS id 96E3C5BCCF; Fri, 23 Jan 2026 16:21:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1769185286; 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=L58AJIr91oTMKf0PXTG1TbeTEeGFV9i4xfX9fFVLhOQ=; b=kiL0wXJJgh1HZq4TCsure9RERmyqII/kPjxCj0kIkQLBiE242PuXZ3NdmN1xgGJ41Jhas1 IX9XioeqvhtuKVp4Y4/0oRdACHfLmwZBu5HPfG1Mik5FaZK0k1xHqTScO5NDFmVSttKrdj KLiereNzlxSMJ07q1vMvgC44Ag96riI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1769185286; 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=L58AJIr91oTMKf0PXTG1TbeTEeGFV9i4xfX9fFVLhOQ=; b=WYSEuCkZ4kAULpe5Rjq1HbLNcgx3KwRNfSAE/H4jyWWJJiGYEXW0r0k+sDTJ6MSMWD0MBI LTTJ7lLo2MfeTSDA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1769185286; 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=L58AJIr91oTMKf0PXTG1TbeTEeGFV9i4xfX9fFVLhOQ=; b=kiL0wXJJgh1HZq4TCsure9RERmyqII/kPjxCj0kIkQLBiE242PuXZ3NdmN1xgGJ41Jhas1 IX9XioeqvhtuKVp4Y4/0oRdACHfLmwZBu5HPfG1Mik5FaZK0k1xHqTScO5NDFmVSttKrdj KLiereNzlxSMJ07q1vMvgC44Ag96riI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1769185286; 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=L58AJIr91oTMKf0PXTG1TbeTEeGFV9i4xfX9fFVLhOQ=; b=WYSEuCkZ4kAULpe5Rjq1HbLNcgx3KwRNfSAE/H4jyWWJJiGYEXW0r0k+sDTJ6MSMWD0MBI LTTJ7lLo2MfeTSDA== 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 697181395E; Fri, 23 Jan 2026 16:21:26 +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 9QNXGQagc2nMGwAAD6G6ig (envelope-from ); Fri, 23 Jan 2026 16:21:26 +0000 Message-ID: Date: Fri, 23 Jan 2026 17:21:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND v3 08/10] mm/vma: improve and document __is_vma_write_locked() Content-Language: en-US To: Suren Baghdasaryan , Lorenzo Stoakes Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Mike Rapoport , Michal Hocko , Shakeel Butt , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt References: <70dcf80f79ecd00a750ea17101061b0949119429.1769086312.git.lorenzo.stoakes@oracle.com> 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-Action: no action X-Stat-Signature: 6mkp6nptrkqj4dfxbu54myx6bepx9tf6 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8C91C80015 X-HE-Tag: 1769185288-835384 X-HE-Meta: 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 4thQ+CL0 lyOYRZG1YPl1zT7tOiFhsEE7FfRtYGO9oMtdl8xIb7c2Xgc5+usjvygx+QmD2ckmPU+vvIbOqY3lh71aRoKWFJKoATaeBPTgw8SqXr4A3fv7wp5KNT8sX09YFO+7RHAmS/lXGxqbRfvIjWS/NM1uWfHqhJodlOaOzKLM4Rq42mq+J8cSxKNxrYE42V5Lg/q50I3NxI8w/BXZK4Z81mkO9Nb8sc81Re+tdIjHjirmAjVFjP+3zzg3f92aBnhH0nLrUmFhwncvhsYR5b5scbXHGr8woDmEnxvLBKZMln5N07Y3cYCiIXqvsPKiA06iKEzgvOHAFX7+M6zkHPa9P5A/eqL56fody2j1Dqf5pJI5FHbrqL/qiuMNTJznO+wweaz6Kivcr6aHTNgntH43rD7K9TWblot3jwKeV1VfCNO+tYSAu3vtAJXgPYlGtorRY6/9huMPK403qfNcz22g= 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 1/22/26 22:55, Suren Baghdasaryan wrote: > On Thu, Jan 22, 2026 at 5:02 AM Lorenzo Stoakes > wrote: >> >> The function is a little confusing, clean it up a little then add a >> descriptive comment. > > I appreciate the descriptive comment but what exactly was confusing in > this function? > >> >> No functional change intended. >> >> Signed-off-by: Lorenzo Stoakes >> --- >> include/linux/mmap_lock.h | 23 ++++++++++++++++++----- >> 1 file changed, 18 insertions(+), 5 deletions(-) >> >> diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h >> index 873bc5f3c97c..b00d34b5ad10 100644 >> --- a/include/linux/mmap_lock.h >> +++ b/include/linux/mmap_lock.h >> @@ -252,17 +252,30 @@ static inline void vma_end_read(struct vm_area_struct *vma) >> vma_refcount_put(vma); >> } >> >> -/* WARNING! Can only be used if mmap_lock is expected to be write-locked */ >> -static inline bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq) >> +/* >> + * Determine whether a VMA is write-locked. Must be invoked ONLY if the mmap >> + * write lock is held. >> + * >> + * Returns true if write-locked, otherwise false. >> + * >> + * Note that mm_lock_seq is updated only if the VMA is NOT write-locked. Could it also say to what it's updated to? Or is it too obvious? > > True, this does not result in a functional change because we do not > use mm_lock_seq if __is_vma_write_locked() succeeds. However this > seems to add additional gotcha that you need to remember. Any reason > why? Actually I wonder if it's really worth returning the mm_lock_seq and passing it to __vma_start_write(), which could just determine it on its own. It would simplify things. >> + */ >> +static inline bool __is_vma_write_locked(struct vm_area_struct *vma, >> + unsigned int *mm_lock_seq) >> { >> - mmap_assert_write_locked(vma->vm_mm); >> + struct mm_struct *mm = vma->vm_mm; >> + const unsigned int seq = mm->mm_lock_seq.sequence; >> + >> + mmap_assert_write_locked(mm); >> >> /* >> * current task is holding mmap_write_lock, both vma->vm_lock_seq and >> * mm->mm_lock_seq can't be concurrently modified. >> */ >> - *mm_lock_seq = vma->vm_mm->mm_lock_seq.sequence; >> - return (vma->vm_lock_seq == *mm_lock_seq); >> + if (vma->vm_lock_seq == seq) >> + return true; >> + *mm_lock_seq = seq; >> + return false; >> } >> >> int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq, >> -- >> 2.52.0