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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-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 17DE4C04F5 X-Stat-Signature: 7wkx5r3fu9wahk84sxexaw7mgh1wirpt X-HE-Tag: 1731570697-503670 X-HE-Meta: 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 rr8lGU7g fRXaeSvOlkPn7VI+R0+nHv9mKtgJgeSCp6e5r4kTtkkjHBIlO410CMt7L5hNbqZp75rN6KUnjhq2cmAvuWYFvAEHX9FvzUD7C8NyHWnD+GD6uiNCtbWycIGaIwGfmraAdD0LwLGyqQ6hMuVHSzzo6c6M/ixt9g9FPtQA7plffsXRy5CZOsCQBYavtFvjMwwMwsPPD8/J/C/nXJ0O29A7DEQMyG0Q5PnX0qUrPWl3fugFjeufUEYJHVjo8eDQSP6D0VVgCahG1FzH0uLbkvotzgyqhq3Brfk7t1vwF 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 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); >> > >