From: Johannes Weiner hannes@cmpxchg.org
mainline inclusion from mainline-v6.10-rc3 commit 7cc5a5d65011983952a9c62f170f5b79e24b1239 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBC4T0
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Christoph reports a page allocator splat triggered by xfstests:
generic/176 214s ... [ 1204.507931] run fstests generic/176 at 2024-05-27 12:52:30 XFS (nvme0n1): Mounting V5 Filesystem cd936307-415f-48a3-b99d-a2d52ae1f273 XFS (nvme0n1): Ending clean mount XFS (nvme1n1): Mounting V5 Filesystem ab3ee1a4-af62-4934-9a6a-6c2fde321850 XFS (nvme1n1): Ending clean mount XFS (nvme1n1): Unmounting Filesystem ab3ee1a4-af62-4934-9a6a-6c2fde321850 XFS (nvme1n1): Mounting V5 Filesystem 7099b02d-9c58-4d1d-be1d-2cc472d12cd9 XFS (nvme1n1): Ending clean mount ------------[ cut here ]------------ page type is 3, passed migratetype is 1 (nr=512) WARNING: CPU: 0 PID: 509870 at mm/page_alloc.c:645 expand+0x1c5/0x1f0 Modules linked in: i2c_i801 crc32_pclmul i2c_smbus [last unloaded: scsi_debug] CPU: 0 PID: 509870 Comm: xfs_io Not tainted 6.10.0-rc1+ #2437 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:expand+0x1c5/0x1f0 Code: 05 16 70 bf 02 01 e8 ca fc ff ff 8b 54 24 34 44 89 e1 48 c7 c7 80 a2 28 83 48 89 c6 b8 01 00 3 RSP: 0018:ffffc90003b2b968 EFLAGS: 00010082 RAX: 0000000000000000 RBX: ffffffff83fa9480 RCX: 0000000000000000 RDX: 0000000000000005 RSI: 0000000000000027 RDI: 00000000ffffffff RBP: 00000000001f2600 R08: 00000000fffeffff R09: 0000000000000001 R10: 0000000000000000 R11: ffffffff83676200 R12: 0000000000000009 R13: 0000000000000200 R14: 0000000000000001 R15: ffffea0007c98000 FS: 00007f72ca3d5780(0000) GS:ffff8881f9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f72ca1fff38 CR3: 00000001aa0c6002 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> ? __warn+0x7b/0x120 ? expand+0x1c5/0x1f0 ? report_bug+0x191/0x1c0 ? handle_bug+0x3c/0x80 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? expand+0x1c5/0x1f0 ? expand+0x1c5/0x1f0 __rmqueue_pcplist+0x3a9/0x730 get_page_from_freelist+0x7a0/0xf00 __alloc_pages_noprof+0x153/0x2e0 __folio_alloc_noprof+0x10/0xa0 __filemap_get_folio+0x16b/0x370 iomap_write_begin+0x496/0x680
While trying to service a movable allocation (page type 1), the page allocator runs into a two-pageblock buddy on the movable freelist whose second block is typed as highatomic (page type 3).
This inconsistency is caused by the highatomic reservation system operating on single pageblocks, while MAX_ORDER can be bigger than that - in this configuration, pageblock_order is 9 while MAX_PAGE_ORDER is 10. The test case is observed to make several adjacent order-3 requests with __GFP_DIRECT_RECLAIM cleared, which marks the surrounding block as highatomic. Upon freeing, the blocks merge into an order-10 buddy. When the highatomic pool is drained later on, this order-10 buddy gets moved back to the movable list, but only the first pageblock is marked movable again. A subsequent expand() of this buddy warns about the tail being of a different type.
This is a long-standing bug that's surfaced by the recent block type warnings added to the allocator. The consequences seem mostly benign, it just results in odd behavior: the highatomic tail blocks are not properly drained, instead they end up on the movable list first, then go back to the highatomic list after an alloc-free cycle.
To fix this, make the highatomic reservation code aware that allocations/buddies can be larger than a pageblock.
While it's an old quirk, the recently added type consistency warnings seem to be the most prominent consequence of it. Set the Fixes: tag accordingly to highlight this backporting dependency.
Link: https://lkml.kernel.org/r/20240530114203.GA1222079@cmpxchg.org Fixes: e0932b6c1f94 ("mm: page_alloc: consolidate free page accounting") Signed-off-by: Johannes Weiner hannes@cmpxchg.org Reported-by: Christoph Hellwig hch@infradead.org Reviewed-by: Zi Yan ziy@nvidia.com Tested-by: Christoph Hellwig hch@lst.de Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Vlastimil Babka vbabka@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/page_alloc.c | 50 +++++++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 16 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4e2ec54b6a7f..53534165b5ab 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1982,10 +1982,12 @@ int find_suitable_fallback(struct free_area *area, unsigned int order, }
/* - * Reserve a pageblock for exclusive use of high-order atomic allocations if - * there are no empty page blocks that contain a page with a suitable order + * Reserve the pageblock(s) surrounding an allocation request for + * exclusive use of high-order atomic allocations if there are no + * empty page blocks that contain a page with a suitable order */ -static void reserve_highatomic_pageblock(struct page *page, struct zone *zone) +static void reserve_highatomic_pageblock(struct page *page, int order, + struct zone *zone) { int mt; unsigned long max_managed, flags; @@ -2011,10 +2013,17 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone) /* Yoink! */ mt = get_pageblock_migratetype(page); /* Only reserve normal pageblocks (i.e., they can merge with others) */ - if (migratetype_is_mergeable(mt)) - if (move_freepages_block(zone, page, mt, - MIGRATE_HIGHATOMIC) != -1) - zone->nr_reserved_highatomic += pageblock_nr_pages; + if (!migratetype_is_mergeable(mt)) + goto out_unlock; + + if (order < pageblock_order) { + if (move_freepages_block(zone, page, mt, MIGRATE_HIGHATOMIC) == -1) + goto out_unlock; + zone->nr_reserved_highatomic += pageblock_nr_pages; + } else { + change_pageblock_range(page, order, MIGRATE_HIGHATOMIC); + zone->nr_reserved_highatomic += 1 << order; + }
out_unlock: spin_unlock_irqrestore(&zone->lock, flags); @@ -2026,7 +2035,7 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone) * intense memory pressure but failed atomic allocations should be easier * to recover from than an OOM. * - * If @force is true, try to unreserve a pageblock even though highatomic + * If @force is true, try to unreserve pageblocks even though highatomic * pageblock is exhausted. */ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, @@ -2068,6 +2077,7 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, * adjust the count once. */ if (is_migrate_highatomic(mt)) { + unsigned long size; /* * It should never happen but changes to * locking could inadvertently allow a per-cpu @@ -2075,9 +2085,9 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, * while unreserving so be safe and watch for * underflows. */ - zone->nr_reserved_highatomic -= min( - pageblock_nr_pages, - zone->nr_reserved_highatomic); + size = max(pageblock_nr_pages, 1UL << order); + size = min(size, zone->nr_reserved_highatomic); + zone->nr_reserved_highatomic -= size; }
/* @@ -2089,11 +2099,19 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, * of pageblocks that cannot be completely freed * may increase. */ - ret = move_freepages_block(zone, page, mt, - ac->migratetype); + if (order < pageblock_order) + ret = move_freepages_block(zone, page, mt, + ac->migratetype); + else { + move_to_free_list(page, zone, order, mt, + ac->migratetype); + change_pageblock_range(page, order, + ac->migratetype); + ret = 1; + } /* - * Reserving this block already succeeded, so this should - * not fail on zone boundaries. + * Reserving the block(s) already succeeded, + * so this should not fail on zone boundaries. */ WARN_ON_ONCE(ret == -1); if (ret > 0) { @@ -3440,7 +3458,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, * if the pageblock should be reserved for the future */ if (unlikely(alloc_flags & ALLOC_HIGHATOMIC)) - reserve_highatomic_pageblock(page, zone); + reserve_highatomic_pageblock(page, order, zone);
return page; } else {