On Fri, 2013-01-04 at 14:08 +0000, Mel Gorman wrote: > Zhouping, please test this patch. > > Andrea and Hugh, any comments on whether this could be improved? > > ---8<--- > mm: thp: Acquire the anon_vma rwsem for lock during split > > Zhouping Liu reported the following against 3.8-rc1 when running a mmap > testcase from LTP. > > [ 588.143072] mapcount 0 page_mapcount 3 > [ 588.147471] ------------[ cut here ]------------ > [ 588.152856] kernel BUG at mm/huge_memory.c:1798! > [ 588.158125] invalid opcode: 0000 [#1] SMP > [ 588.162882] Modules linked in: ip6table_filter ip6_tables ebtable_nat ebtables bnep bluetooth rfkill iptable_mangle ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter > +ip_tables be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi vfat fat > +dm_mirror dm_region_hash dm_log dm_mod cdc_ether iTCO_wdt i7core_edac coretemp usbnet iTCO_vendor_support mii crc32c_intel edac_core lpc_ich shpchp ioatdma mfd_core i2c_i801 pcspkr serio_raw bnx2 microcode dca > +vhost_net tun macvtap macvlan kvm_intel kvm uinput mgag200 sr_mod cdrom i2c_algo_bit sd_mod drm_kms_helper crc_t10dif ata_generic pata_acpi ttm ata_piix drm libata i2c_core megaraid_sas > > [ 588.246517] CPU 1 > [ 588.248636] Pid: 23217, comm: mmap10 Not tainted 3.8.0-rc1mainline+ #17 IBM IBM System x3400 M3 Server -[7379I08]-/69Y4356 > [ 588.262171] RIP: 0010:[<ffffffff8118fac7>] [<ffffffff8118fac7>] __split_huge_page+0x677/0x6d0 > [ 588.272067] RSP: 0000:ffff88017a03fc08 EFLAGS: 00010293 > [ 588.278235] RAX: 0000000000000003 RBX: ffff88027a6c22e0 RCX: 00000000000034d2 > [ 588.286394] RDX: 000000000000748b RSI: 0000000000000046 RDI: 0000000000000246 > [ 588.294216] RBP: ffff88017a03fcb8 R08: ffffffff819d2440 R09: 000000000000054a > [ 588.302441] R10: 0000000000aaaaaa R11: 00000000ffffffff R12: 0000000000000000 > [ 588.310495] R13: 00007f4f11a00000 R14: ffff880179e96e00 R15: ffffea0005c08000 > [ 588.318640] FS: 00007f4f11f4a740(0000) GS:ffff88017bc20000(0000) knlGS:0000000000000000 > [ 588.327894] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 588.334569] CR2: 00000037e9ebb404 CR3: 000000017a436000 CR4: 00000000000007e0 > [ 588.342718] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 588.350861] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > [ 588.359134] Process mmap10 (pid: 23217, threadinfo ffff88017a03e000, task ffff880172dd32e0) > [ 588.368667] Stack: > [ 588.370960] ffff88017a540ec8 ffff88017a03fc20 ffffffff816017b5 ffff88017a03fc88 > [ 588.379566] ffffffff812fa014 0000000000000000 ffff880279ebd5c0 00000000f4f11a4c > [ 588.388150] 00000007f4f11f49 00000007f4f11a00 ffff88017a540ef0 ffff88017a540ee8 > [ 588.396711] Call Trace: > [ 588.455106] [<ffffffff816017b5>] ? rwsem_down_read_failed+0x15/0x17 > [ 588.518106] [<ffffffff812fa014>] ? call_rwsem_down_read_failed+0x14/0x30 > [ 588.580897] [<ffffffff815ffc04>] ? down_read+0x24/0x2b > [ 588.642630] [<ffffffff8118fb88>] split_huge_page+0x68/0xb0 > [ 588.703814] [<ffffffff81190ed4>] __split_huge_page_pmd+0x134/0x330 > [ 588.766064] [<ffffffff8104b997>] ? pte_alloc_one+0x37/0x50 > [ 588.826460] [<ffffffff81191121>] split_huge_page_pmd_mm+0x51/0x60 > [ 588.887746] [<ffffffff8119116b>] split_huge_page_address+0x3b/0x50 > [ 588.948673] [<ffffffff8119121c>] __vma_adjust_trans_huge+0x9c/0xf0 > [ 589.008660] [<ffffffff811650f4>] vma_adjust+0x684/0x750 > [ 589.066328] [<ffffffff811653ba>] __split_vma.isra.28+0x1fa/0x220 > [ 589.123497] [<ffffffff810135d1>] ? __switch_to+0x181/0x4a0 > [ 589.180704] [<ffffffff811661a9>] do_munmap+0xf9/0x420 > [ 589.237461] [<ffffffff8160026c>] ? __schedule+0x3cc/0x7b0 > [ 589.294520] [<ffffffff8116651e>] vm_munmap+0x4e/0x70 > [ 589.350784] [<ffffffff8116741b>] sys_munmap+0x2b/0x40 > [ 589.406971] [<ffffffff8160a159>] system_call_fastpath+0x16/0x1b > > Alexander Beregalov reported a very similar bug and Hillf Danton identified > that commit 5a505085 (mm/rmap: Convert the struct anon_vma::mutex to an > rwsem) and commit 4fc3f1d6 (mm/rmap, migration: Make rmap_walk_anon() > and try_to_unmap_anon() more scalable) were likely the problem. Reverting > these commits was reported to solve the problem. > > Despite the reason for these commits, NUMA balancing is not the direct > source of the problem. split_huge_page() expected the anon_vma lock to be > exclusive to serialise the whole split operation. Ordinarily it is expected > that the anon_vma lock would only be required when updating the avcs but > THP also uses it. The locking requirements for THP are complex and there > is some overlap but broadly speaking they include the following > > 1. mmap_sem for read or write prevents THPs being created underneath > 2. anon_vma is taken for write if collapsing a huge page > 3. mm->page_table_lock should be taken when checking if pmd_trans_huge as > split_huge_page can run in parallel > 4. wait_split_huge_page uses anon_vma taken for write mode to serialise > against other THP operations > 5. compound_lock is used to serialise between > __split_huge_page_refcount() and gup Can't find gup path hold compound_lock. > > split_huge_page takes anon_vma for read but that does not serialise against > parallel split_huge_page operations on the same page (rule 2). One process > could be modifying the ref counts while the other modifies the page tables > leading to counters not being reliable. This patch takes the anon_vma > lock for write to serialise against parallel split_huge_page and parallel > collapse operations as it is the most fine-grained lock available that > protects against both. > > Reported-by: Zhouping Liu <zliu@xxxxxxxxxx> > Reported-by: Alexander Beregalov <a.beregalov@xxxxxxxxx> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> > --- > mm/huge_memory.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 9e894ed..6001ee6 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1819,9 +1819,19 @@ int split_huge_page(struct page *page) > > BUG_ON(is_huge_zero_pfn(page_to_pfn(page))); > BUG_ON(!PageAnon(page)); > - anon_vma = page_lock_anon_vma_read(page); > + > + /* > + * The caller does not necessarily hold an mmap_sem that would prevent > + * the anon_vma disappearing so we first we take a reference to it > + * and then lock the anon_vma for write. This is similar to > + * page_lock_anon_vma_read except the write lock is taken to serialise > + * against parallel split or collapse operations. > + */ > + anon_vma = page_get_anon_vma(page); > if (!anon_vma) > goto out; > + anon_vma_lock_write(anon_vma); > + > ret = 0; > if (!PageCompound(page)) > goto out_unlock; > @@ -1832,7 +1842,8 @@ int split_huge_page(struct page *page) > > BUG_ON(PageCompound(page)); > out_unlock: > - page_unlock_anon_vma_read(anon_vma); > + anon_vma_unlock(anon_vma); > + put_anon_vma(anon_vma); > out: > return ret; > } > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . 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