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To: Vlastimil Babka , 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> From: Kemeng Shi Message-ID: <56ee8988-fd25-76bf-08a8-b84732fd2170@huaweicloud.com> Date: Thu, 14 Nov 2024 17:21:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <2b6ca5b1-f421-4dda-a2a2-865af97b2db8@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgA3l+MrwTVn9jH2Bg--.34094S2 X-Coremail-Antispam: 1UD129KBjvJXoW7CFy3XFy8Ww4kGF4fXw4kXrb_yoW8ZF4Dpa 4DKa4xWF18u34j9FnFyw45ZF47Z392yF47Jws8KFy8AFnYyas7tr90yry8ZryqqrnxArWq vrsrKFZxCan0vaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkEb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxk0xIA0c2IEe2xFo4CEbIxvr21lc7CjxVAaw2AF wI0_JF0_Jw1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4 xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r126r1D MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I 0E14v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWU JVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x07jjVb kUUUUU= X-CM-SenderInfo: 5vklyvpphqwq5kxd4v5lfo033gof0z/ X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F31DA206FF X-Stat-Signature: wiwy9sm6oaqoqw5gmfqrba9hcdt6x5bp X-Rspam-User: X-HE-Tag: 1731576070-948402 X-HE-Meta: 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 wYq4JFTA LS6BxruyuCE1brAW08wJ+cBJu0CYpvtUxHbdKexDWm0cwJuHDR6UGqTTrQ4qjEs4aoMmVk9SlUrpjdU4MNaJvRqPthO4kC+NtBpFYQHQg/IxBmtH5aFoy6OOmSA== 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: 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. 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); >> >