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Content-Language: en-US To: Kemeng Shi , Qiang Liu , baolin.wang@linux.alibaba.com 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> <56ee8988-fd25-76bf-08a8-b84732fd2170@huaweicloud.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+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: <56ee8988-fd25-76bf-08a8-b84732fd2170@huaweicloud.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 81A5612067C X-Stat-Signature: q3ynz7f7obwsjazxz7mksdtiuxui6cmr X-Rspam-User: X-HE-Tag: 1731576966-627847 X-HE-Meta: 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 Rq3cBffF R5BswNEOA/EPQHfDWtlAu39osA/NkigGPNuRKLq5L52iZzpWm+2i/bLtL6l84ijpcLB5xdNQeZDORAByxVulBB/4diLxONxCCrwJTJldTpJKsJC39uSfSkj98n+5QmKJWsnLYq76WVJpTeBXc22byqOHK9Avj4T8N4rzEVNBpm2G+LlqYX6+ua+VMmrkJLhwZ4kZM4v13nj932oLHbZ/44fAej8aNN3fElDZDLG1OtJKhPnNkmJO1ktV6RkJnweVwFA7QNf/Tji8QpFB9D3SO0lZ2kteG1GecMPy0 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 11/14/24 10:21, Kemeng Shi wrote: > > Hello > on 11/14/2024 3:44 PM, 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 >> > As stride could 32, if isolate_freepages_range() is called with start_pfn not > aligned with 32, we could bail out look with blockpfn > end_pfn in > isolate_freepages_block(). Please correct if I miss something. >> I see that's since 3da0272a4c7d ("mm/compaction: correctly return failure >> with bogus compound_order in strict mode") >> >> 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? > As order of pageblock is <= MAX_ORDER, if bogus order is > MAX_ORDER, then > blockpfn + (1UL << order) must be > end_pfn, I think the sanity check is > not needed. Hm I guess we could only overflow with blockpfn being initially >= 1UL << 63 and reading a bogus order of 63. So it can't realistically happen. > Thanks. > Kemeng >> >>> --- >>> 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); >>> >> >