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Wed, 01 Oct 2025 20:31:48 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6376b3b8625sm1011005a12.18.2025.10.01.20.31.46 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 01 Oct 2025 20:31:46 -0700 (PDT) From: Wei Yang To: akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, iamjoonsoo.kim@lge.com Cc: linux-mm@kvack.org, Wei Yang Subject: [PATCH 2/2] mm/compaction: fix the range to pageblock_pfn_to_page() Date: Thu, 2 Oct 2025 03:31:40 +0000 Message-Id: <20251002033140.24462-3-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20251002033140.24462-1-richard.weiyang@gmail.com> References: <20251002033140.24462-1-richard.weiyang@gmail.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D3500180005 X-Stat-Signature: io5us11yp8nb8cdyf7qr5xzs3gzwudg6 X-Rspam-User: X-HE-Tag: 1759375909-906801 X-HE-Meta: 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 R+8sfx/3 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 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: Current code may skip some part of the range to pageblock_pfn_to_page() to check whether the range is in the same zone. Function pageblock_pfn_to_page() is first introduced by commit 7d49d8868336 ("mm, compaction: reduce zone checking frequency in the migration scanner"), in which it checks and isolates on the same range [pfn, block_end_pfn]. While after commit e1409c325fdc ("mm/compaction: pass only pageblock aligned range to pageblock_pfn_to_page"), we operate on two different ranges for check and isolation. * [block_start_pfn, block_end_pfn] to check it is in the same zone * [pfn, block_end_pfn] to do isolation It miss some range to check when start_pfn and zone->zone_start_pfn is in the same pageblock but (start_pfn < zone->zone_start_pfn). The range before zone_start_pfn is missed. start_pfn zone_start_pfn +----+-------------+-------------------+ block_start_pfn block_end_pfn This leads to the range check is passed, but it will isolate a range in two different zones. Let's use the same [block_start_pfn, block_end_pfn] for each iteration to represent the range to check and isolate. Fixes: e1409c325fdc ("mm/compaction: pass only pageblock aligned range to pageblock_pfn_to_page") Signed-off-by: Wei Yang Cc: Vlastimil Babka Cc: Joonsoo Kim --- mm/compaction.c | 37 ++++++++++++++----------------------- 1 file changed, 14 insertions(+), 23 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 1e8f8eca318c..8760d10bd0b3 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1320,27 +1320,22 @@ int isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, unsigned long end_pfn) { - unsigned long pfn, block_start_pfn, block_end_pfn; + unsigned long block_start_pfn, block_end_pfn; int ret = 0; /* Scan block by block. First and last block may be incomplete */ - pfn = start_pfn; - block_start_pfn = pageblock_start_pfn(pfn); - if (block_start_pfn < cc->zone->zone_start_pfn) - block_start_pfn = cc->zone->zone_start_pfn; - block_end_pfn = pageblock_end_pfn(pfn); + block_start_pfn = start_pfn; + block_end_pfn = pageblock_end_pfn(start_pfn); - for (; pfn < end_pfn; pfn = block_end_pfn, - block_start_pfn = block_end_pfn, + for (; block_start_pfn < end_pfn; block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { block_end_pfn = min(block_end_pfn, end_pfn); - if (!pageblock_pfn_to_page(block_start_pfn, - block_end_pfn, cc->zone)) + if (!pageblock_pfn_to_page(block_start_pfn, block_end_pfn, cc->zone)) continue; - ret = isolate_migratepages_block(cc, pfn, block_end_pfn, + ret = isolate_migratepages_block(cc, block_start_pfn, block_end_pfn, ISOLATE_UNEVICTABLE); if (ret) @@ -2046,7 +2041,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) { unsigned long block_start_pfn; unsigned long block_end_pfn; - unsigned long low_pfn; struct page *page; const isolate_mode_t isolate_mode = (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | @@ -2058,20 +2052,17 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) * initialized by compact_zone(). The first failure will use * the lowest PFN as the starting point for linear scanning. */ - low_pfn = fast_find_migrateblock(cc); - block_start_pfn = pageblock_start_pfn(low_pfn); - if (block_start_pfn < cc->zone->zone_start_pfn) - block_start_pfn = cc->zone->zone_start_pfn; + block_start_pfn = fast_find_migrateblock(cc); /* * fast_find_migrateblock() has already ensured the pageblock is not * set with a skipped flag, so to avoid the isolation_suitable check * below again, check whether the fast search was successful. */ - fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; + fast_find_block = block_start_pfn != cc->migrate_pfn && !cc->fast_search_fail; /* Only scan within a pageblock boundary */ - block_end_pfn = pageblock_end_pfn(low_pfn); + block_end_pfn = pageblock_end_pfn(block_start_pfn); /* * Iterate over whole pageblocks until we find the first suitable. @@ -2079,7 +2070,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) */ for (; block_end_pfn <= cc->free_pfn; fast_find_block = false, - cc->migrate_pfn = low_pfn = block_end_pfn, + cc->migrate_pfn = block_end_pfn, block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { @@ -2088,7 +2079,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) * many pageblocks unsuitable, so periodically check if we * need to schedule. */ - if (!(low_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) + if (!(block_start_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) cond_resched(); page = pageblock_pfn_to_page(block_start_pfn, @@ -2109,8 +2100,8 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) * before making it "skip" so other compaction instances do * not scan the same block. */ - if ((pageblock_aligned(low_pfn) || - low_pfn == cc->zone->zone_start_pfn) && + if ((pageblock_aligned(block_start_pfn) || + block_start_pfn == cc->zone->zone_start_pfn) && !fast_find_block && !isolation_suitable(cc, page)) continue; @@ -2128,7 +2119,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) } /* Perform the isolation */ - if (isolate_migratepages_block(cc, low_pfn, block_end_pfn, + if (isolate_migratepages_block(cc, block_start_pfn, block_end_pfn, isolate_mode)) return ISOLATE_ABORT; -- 2.34.1