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 E95211EABAB for ; Thu, 14 Nov 2024 07:52:22 +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=1731570745; cv=none; b=IiRe8NFUYULzOUXV1bdbn1eEPrxbL2QaQqMsaJ4GLBFJ36WzNcoJOcbab7UtnGASxpCVVcoKQSSPWCLiIp8m5H7/k977GI0Fsd6GbK5iDR8nYBmt5xEVGKNXSqKsVkMCMaQM1SmfiYHfXnkXsIeqqmWT46lHKpXWYS029w0zkzs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731570745; c=relaxed/simple; bh=YvIPzQ4ESV2et8xD4F+yHEJAVV77Z3dmui/A1sUlMok=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=f9kB7CfWqu9DTT/BrP9QIl2RflXwLLyWXK2MsISC3Yk4XSpvVLrd3M+fqDAzwlj4ucMSimgNWNARg+Ok1OpH2JsiLGVfBfqi4mxPideshiC0qwejYXb49khHfq1Z5OCjTR7RV+gOitspmg//wzzg4RG1t9/TyehBBXKTEKd2Z2c= 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=V9gHOWmE; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=qZgF7dN7; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=V9gHOWmE; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=qZgF7dN7; 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="V9gHOWmE"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="qZgF7dN7"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="V9gHOWmE"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="qZgF7dN7" Received: from imap1.dmz-prg2.suse.org (unknown [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 0364121979; Thu, 14 Nov 2024 07:52:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1731570741; 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=WQ4uIaR8EC9zCCXZjp5UewO6FD29d7j31WBEEqB9OUE=; b=V9gHOWmEwuYU+gnLWkvmJaIW/JmbOZwdhPDN5DBf46No1EWIL2/j6h41yunv+VN6dohw1M nBLPI631VJwHupvkdkOpS+9P/CJIk/QmPRDUP4zFOg993eqlq/lv3D90WpFiqE70Gi7IfH SZ2dWu69Nh8A+2WGs8Zt5JDqtHbe0ig= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1731570741; 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=WQ4uIaR8EC9zCCXZjp5UewO6FD29d7j31WBEEqB9OUE=; b=qZgF7dN7+fjEBlLo4+PFJSqGil1iQivj/EqGBNB3qpQW6g+Pg88wHOKO2/Pjq/gjEk4sE4 JYjb5AD8Y/FJEDAg== Authentication-Results: smtp-out1.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1731570741; 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=WQ4uIaR8EC9zCCXZjp5UewO6FD29d7j31WBEEqB9OUE=; b=V9gHOWmEwuYU+gnLWkvmJaIW/JmbOZwdhPDN5DBf46No1EWIL2/j6h41yunv+VN6dohw1M nBLPI631VJwHupvkdkOpS+9P/CJIk/QmPRDUP4zFOg993eqlq/lv3D90WpFiqE70Gi7IfH SZ2dWu69Nh8A+2WGs8Zt5JDqtHbe0ig= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1731570741; 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=WQ4uIaR8EC9zCCXZjp5UewO6FD29d7j31WBEEqB9OUE=; b=qZgF7dN7+fjEBlLo4+PFJSqGil1iQivj/EqGBNB3qpQW6g+Pg88wHOKO2/Pjq/gjEk4sE4 JYjb5AD8Y/FJEDAg== 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 E336F13794; Thu, 14 Nov 2024 07:52:20 +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 g3nYNjSsNWf+agAAD6G6ig (envelope-from ); Thu, 14 Nov 2024 07:52:20 +0000 Message-ID: Date: Thu, 14 Nov 2024 08:52:20 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/compaction: remove unnecessary detection code. Content-Language: en-US From: Vlastimil Babka To: Qiang Liu , baolin.wang@linux.alibaba.com, Kemeng Shi , Baolin Wang Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241114065720.3665-1-liuq131@chinatelecom.cn> <2b6ca5b1-f421-4dda-a2a2-865af97b2db8@suse.cz> 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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <2b6ca5b1-f421-4dda-a2a2-865af97b2db8@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:mid] X-Spam-Flag: NO X-Spam-Level: On 11/14/24 08:44, Vlastimil Babka wrote: > On 11/14/24 07:57, Qiang Liu wrote: >> It is impossible for the situation where blockpfn > end_pfn to arise, >> The if statement here is not only unnecessary, but may also lead to >> a misunderstanding that blockpfn > end_pfn could potentially happen. >> so these unnecessary checking code should be removed. >> >> Signed-off-by: Qiang Liu > > I see that's since 3da0272a4c7d ("mm/compaction: correctly return failure > with bogus compound_order in strict mode") Hm but we still have: for (; blockpfn < end_pfn; blockpfn += stride, page += stride) { and this advance by stride can mix up with advance by isolated, initial pfn might not be aligned... I don't see any guarantee that the for loop will exit with exactly blockpfn == end_pfn, it may easily advance beyond end_pfn so we shouldn't remove the check? > I think that commit introduced a risk of overflow due to a bogus order > (which we read in a racy way), and once blockpfn overflows it will satisfy > <= end_pfn and might e.g. end up scanning a completely different zone? > > if (blockpfn + (1UL << order) <= end_pfn) { > > blockpfn += (1UL << order) - 1; > page += (1UL << order) - 1; > nr_scanned += (1UL << order) - 1; > } > > We should better add back the MAX_ORDER sanity check? > >> --- >> mm/compaction.c | 6 ------ >> 1 file changed, 6 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index a2b16b08cbbf..baeda7132252 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -682,12 +682,6 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, >> if (locked) >> spin_unlock_irqrestore(&cc->zone->lock, flags); >> >> - /* >> - * Be careful to not go outside of the pageblock. >> - */ >> - if (unlikely(blockpfn > end_pfn)) >> - blockpfn = end_pfn; >> - >> trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, >> nr_scanned, total_isolated); >> > >