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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2012-10-08 16:30:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:30 +0900
commit75077afbec1ac89178c1542b23a70d0f960b0aaf (patch)
tree843b8a7175de7a9a2dca37d877cd742121f4b627 /arch/s390/mm/gup.c
parent8e72033f2a489b6c98c4e3c7cc281b1afd6cb85c (diff)
downloadop-kernel-dev-75077afbec1ac89178c1542b23a70d0f960b0aaf.zip
op-kernel-dev-75077afbec1ac89178c1542b23a70d0f960b0aaf.tar.gz
thp, s390: thp splitting backend for s390
This patch is part of the architecture backend for thp on s390. It provides the functions related to thp splitting, including serialization against gup. Unlike other archs, pmdp_splitting_flush() cannot use a tlb flushing operation to serialize against gup on s390, because that wouldn't be stopped by the disabled IRQs. So instead, smp_call_function() is called with an empty function, which will have the expected effect. Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Hillf Danton <dhillf@gmail.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/s390/mm/gup.c')
-rw-r--r--arch/s390/mm/gup.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index eeaf802..60acb93 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -115,7 +115,16 @@ static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
pmd = *pmdp;
barrier();
next = pmd_addr_end(addr, end);
- if (pmd_none(pmd))
+ /*
+ * The pmd_trans_splitting() check below explains why
+ * pmdp_splitting_flush() has to serialize with
+ * smp_call_function() against our disabled IRQs, to stop
+ * this gup-fast code from running while we set the
+ * splitting bit in the pmd. Returning zero will take
+ * the slow path that will call wait_split_huge_page()
+ * if the pmd is still in splitting state.
+ */
+ if (pmd_none(pmd) || pmd_trans_splitting(pmd))
return 0;
if (unlikely(pmd_huge(pmd))) {
if (!gup_huge_pmd(pmdp, pmd, addr, next,
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