From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id EF8B92C00B2 for ; Wed, 1 Jan 2014 20:54:08 +1100 (EST) Received: from /spool/local by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 Jan 2014 19:54:03 +1000 Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [9.190.234.120]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id D13EB3578052 for ; Wed, 1 Jan 2014 20:54:00 +1100 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s019ZMU59175384 for ; Wed, 1 Jan 2014 20:35:23 +1100 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s019rxtB008162 for ; Wed, 1 Jan 2014 20:53:59 +1100 From: "Aneesh Kumar K.V" To: benh@kernel.crashing.org, paulus@samba.org, aarcange@redhat.com, kirill.shutemov@linux.intel.com Subject: [PATCH] powerpc: thp: Fix crash on mremap Date: Wed, 1 Jan 2014 15:23:47 +0530 Message-Id: <1388570027-22933-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: "Aneesh Kumar K.V" This patch fix the below crash NIP [c00000000004cee4] .__hash_page_thp+0x2a4/0x440 LR [c0000000000439ac] .hash_page+0x18c/0x5e0 ... Call Trace: [c000000736103c40] [00001ffffb000000] 0x1ffffb000000(unreliable) [437908.479693] [c000000736103d50] [c0000000000439ac] .hash_page+0x18c/0x5e0 [437908.479699] [c000000736103e30] [c00000000000924c] .do_hash_page+0x4c/0x58 On ppc64 we use the pgtable for storing the hpte slot information and store address to the pgtable at a constant offset (PTRS_PER_PMD) from pmd. On mremap, when we switch the pmd, we need to withdraw and deposit the pgtable again, so that we find the pgtable at PTRS_PER_PMD offset from new pmd. We also want to move the withdraw and deposit before the set_pmd so that, when page fault find the pmd as trans huge we can be sure that pgtable can be located at the offset. Signed-off-by: Aneesh Kumar K.V --- NOTE: For other archs we would just be removing the pgtable from the list and adding it back. I didn't find an easy way to make it not do that without lots of #ifdef around. Any suggestion around that is welcome. mm/huge_memory.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7de1bf85f683..eb2e60d9ba45 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1500,24 +1500,23 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, */ ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); if (ret == 1) { + pgtable_t pgtable; + new_ptl = pmd_lockptr(mm, new_pmd); if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); VM_BUG_ON(!pmd_none(*new_pmd)); + /* + * Archs like ppc64 use pgtable to store per pmd + * specific information. So when we switch the pmd, + * we should also withdraw and deposit the pgtable + */ + pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); + pgtable_trans_huge_deposit(mm, new_pmd, pgtable); set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); - if (new_ptl != old_ptl) { - pgtable_t pgtable; - - /* - * Move preallocated PTE page table if new_pmd is on - * different PMD page table. - */ - pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); - pgtable_trans_huge_deposit(mm, new_pmd, pgtable); - + if (new_ptl != old_ptl) spin_unlock(new_ptl); - } spin_unlock(old_ptl); } out: -- 1.8.3.2