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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2017-02-24 14:59:16 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:56 -0800
commit288bc54949fc2625a4fd811a188fb200cc498946 (patch)
tree29a5581d821429a6b0783544fc002acb4a953a99 /mm/mprotect.c
parentcee216a696b2004017a5ecb583366093d90b1568 (diff)
downloadlwn-288bc54949fc2625a4fd811a188fb200cc498946.tar.gz
lwn-288bc54949fc2625a4fd811a188fb200cc498946.zip
mm/autonuma: let architecture override how the write bit should be stashed in a protnone pte.
Patch series "Numabalancing preserve write fix", v2. This patch series address an issue w.r.t THP migration and autonuma preserve write feature. migrate_misplaced_transhuge_page() cannot deal with concurrent modification of the page. It does a page copy without following the migration pte sequence. IIUC, this was done to keep the migration simpler and at the time of implemenation we didn't had THP page cache which would have required a more elaborate migration scheme. That means thp autonuma migration expect the protnone with saved write to be done such that both kernel and user cannot update the page content. This patch series enables archs like ppc64 to do that. We are good with the hash translation mode with the current code, because we never create a hardware page table entry for a protnone pte. This patch (of 2): Autonuma preserves the write permission across numa fault to avoid taking a writefault after a numa fault (Commit: b191f9b106ea " mm: numa: preserve PTE write permissions across a NUMA hinting fault"). Architecture can implement protnone in different ways and some may choose to implement that by clearing Read/ Write/Exec bit of pte. Setting the write bit on such pte can result in wrong behaviour. Fix this up by allowing arch to override how to save the write bit on a protnone pte. [aneesh.kumar@linux.vnet.ibm.com: don't mark pte saved write in case of dirty_accountable] Link: http://lkml.kernel.org/r/1487942884-16517-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com [aneesh.kumar@linux.vnet.ibm.com: v3] Link: http://lkml.kernel.org/r/1487498625-10891-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/1487050314-3892-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: Michael Neuling <mikey@neuling.org> Cc: Rik van Riel <riel@surriel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <michaele@au1.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mprotect.c')
-rw-r--r--mm/mprotect.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
index a45b4dc6a7f5..848e946b08e5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -99,7 +99,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
ptent = ptep_modify_prot_start(mm, addr, pte);
ptent = pte_modify(ptent, newprot);
if (preserve_write)
- ptent = pte_mkwrite(ptent);
+ ptent = pte_mk_savedwrite(ptent);
/* Avoid taking write faults for known dirty pages */
if (dirty_accountable && pte_dirty(ptent) &&