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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pH2ge-007qS8-EQ; Sun, 15 Jan 2023 13:04:36 +0000 Date: Sun, 15 Jan 2023 13:04:36 +0000 From: Matthew Wilcox To: Sergey Senozhatsky Cc: Andrew Morton , Mike Kravetz , Minchan Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv2 0/4] zsmalloc: make zspage chain size configurable Message-ID: References: <20230109033838.2779902-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: C02C140010 X-Rspamd-Server: rspam01 X-Stat-Signature: mjrbmbobzfueqggr583a119tewh4igtu X-HE-Tag: 1673787885-937791 X-HE-Meta: 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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: On Sun, Jan 15, 2023 at 04:18:55PM +0900, Sergey Senozhatsky wrote: > So this warning is move_to_new_folio() being called on un-isolated > src folio. I had DEBUG_VM disabled so VM_BUG_ON_FOLIO(!folio_test_isolated(src)) > did nothing, however after mops->migrate_page() it would trigger WARN_ON() > because it evaluates folio_test_isolated(src) one more time: > > [ 59.500580] page:0000000097d97a42 refcount:2 mapcount:1665 mapping:0000000000000000 index:0xffffea00185ce940 pfn:0x113dc4 > [ 59.503239] flags: 0x8000000000000001(locked|zone=2) > [ 59.505060] raw: 8000000000000001 ffffea00044f70c8 ffffc90000ba7c20 ffffffff81c22582 > [ 59.507288] raw: ffffea00185ce940 ffff88809183fdb0 0000000200000680 0000000000000000 That is quite the messed-up page. mapcount is positive, but higher than refcount. And not just a little bit; 1665 vs 2. But mapping is NULL, so it's not anon or file memory. Makes me think it belongs to a driver that's using ->mapcount for its own purposes. It's not PageSlab. Given that you're working on zsmalloc, I took a look and: static inline void set_first_obj_offset(struct page *page, unsigned int offset) { page->page_type = offset; } (page_type aliases with mapcount). So I'm pretty sure this is a zsmalloc page. But mapping should point to zsmalloc_mops. Not really sure what's going on here. Can you bisect? > [ 59.509622] page dumped because: VM_BUG_ON_FOLIO(!folio_test_isolated(src)) > [ 59.511845] ------------[ cut here ]------------ > [ 59.513181] kernel BUG at mm/migrate.c:988! > [ 59.514821] invalid opcode: 0000 [#1] PREEMPT SMP PTI > > [ 59.523018] RIP: 0010:move_to_new_folio+0x362/0x3b0 > [ 59.524160] Code: ff ff e9 55 fd ff ff 48 89 df e8 69 d8 ff ff f0 80 60 02 fb 31 c0 e9 65 fd ff ff 48 c7 c6 00 f5 e9 81 48 89 df e8 be c0 f9 ff <0f> 0b 48 c7 c6 00 f5 e9 81 48 89 df e8 ad c0 f9 ff 0f 0b b8 f5 ff > [ 59.528349] RSP: 0018:ffffc90000ba7af8 EFLAGS: 00010246 > [ 59.529551] RAX: 000000000000003f RBX: ffffea00044f7100 RCX: 0000000000000000 > [ 59.531186] RDX: 0000000000000000 RSI: ffffffff81e8dcf1 RDI: 00000000ffffffff > [ 59.532790] RBP: ffffea00184f1140 R08: 00000000ffffbfff R09: 00000000ffffbfff > [ 59.534392] R10: ffff888621ca0000 R11: ffff888621ca0000 R12: 8000000000000001 > [ 59.536026] R13: 0000000000000001 R14: 0000000000000000 R15: ffffea00184f1140 > [ 59.537646] FS: 0000000000000000(0000) GS:ffff888626a00000(0000) knlGS:0000000000000000 > [ 59.539484] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 59.540785] CR2: 00007ff7fbed8000 CR3: 0000000101a26001 CR4: 0000000000770ee0 > [ 59.542412] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 59.544030] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 59.545637] PKRU: 55555554 > [ 59.546261] Call Trace: > [ 59.546833] > [ 59.547371] ? lock_is_held_type+0xd9/0x130 > [ 59.548331] migrate_pages_batch+0x650/0xdc0 > [ 59.549326] ? move_freelist_tail+0xc0/0xc0 > [ 59.550281] ? isolate_freepages+0x290/0x290 > [ 59.551289] ? folio_flags.constprop.0+0x50/0x50 > [ 59.552348] migrate_pages+0x3fa/0x4d0 > [ 59.553224] ? isolate_freepages+0x290/0x290 > [ 59.554214] ? move_freelist_tail+0xc0/0xc0 > [ 59.555173] compact_zone+0x51b/0x6a0 > [ 59.556031] proactive_compact_node+0x8e/0xe0 > [ 59.557033] kcompactd+0x1c3/0x350 > [ 59.557842] ? swake_up_all+0xe0/0xe0 > [ 59.558699] ? kcompactd_do_work+0x260/0x260 > [ 59.559703] kthread+0xec/0x110 > [ 59.560450] ? kthread_complete_and_exit+0x20/0x20 > [ 59.561582] ret_from_fork+0x1f/0x30 > [ 59.562427] > [ 59.562966] Modules linked in: deflate zlib_deflate zstd zstd_compress zram > [ 59.564591] ---[ end trace 0000000000000000 ]--- > [ 59.565661] RIP: 0010:move_to_new_folio+0x362/0x3b0 > [ 59.566802] Code: ff ff e9 55 fd ff ff 48 89 df e8 69 d8 ff ff f0 80 60 02 fb 31 c0 e9 65 fd ff ff 48 c7 c6 00 f5 e9 81 48 89 df e8 be c0 f9 ff <0f> 0b 48 c7 c6 00 f5 e9 81 48 89 df e8 ad c0 f9 ff 0f 0b b8 f5 ff > [ 59.571048] RSP: 0018:ffffc90000ba7af8 EFLAGS: 00010246 > [ 59.572257] RAX: 000000000000003f RBX: ffffea00044f7100 RCX: 0000000000000000 > [ 59.573906] RDX: 0000000000000000 RSI: ffffffff81e8dcf1 RDI: 00000000ffffffff > [ 59.575544] RBP: ffffea00184f1140 R08: 00000000ffffbfff R09: 00000000ffffbfff > [ 59.577236] R10: ffff888621ca0000 R11: ffff888621ca0000 R12: 8000000000000001 > [ 59.578893] R13: 0000000000000001 R14: 0000000000000000 R15: ffffea00184f1140 > [ 59.580593] FS: 0000000000000000(0000) GS:ffff888626a00000(0000) knlGS:0000000000000000 > [ 59.582432] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 59.583767] CR2: 00007ff7fbed8000 CR3: 0000000101a26001 CR4: 0000000000770ee0 > [ 59.585437] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 59.587082] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 59.588738] PKRU: 55555554