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authorAl Viro <viro@zeniv.linux.org.uk>2016-07-01 05:34:49 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2016-07-01 05:34:49 +0200
commitb223f4e215b32849b841e750e83a915b670070f5 (patch)
tree75340f6305028de331a17255018869822b3886d2 /mm/hugetlb.c
parentRemove last traces of ->sync_page (diff)
parentvfs: clean up documentation (diff)
downloadlinux-b223f4e215b32849b841e750e83a915b670070f5.tar.xz
linux-b223f4e215b32849b841e750e83a915b670070f5.zip
Merge branch 'd_real' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into work.misc
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c46
1 files changed, 42 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b322c85c58c3..df3c17603a0d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -832,8 +832,27 @@ static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
* Only the process that called mmap() has reserves for
* private mappings.
*/
- if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
- return true;
+ if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
+ /*
+ * Like the shared case above, a hole punch or truncate
+ * could have been performed on the private mapping.
+ * Examine the value of chg to determine if reserves
+ * actually exist or were previously consumed.
+ * Very Subtle - The value of chg comes from a previous
+ * call to vma_needs_reserves(). The reserve map for
+ * private mappings has different (opposite) semantics
+ * than that of shared mappings. vma_needs_reserves()
+ * has already taken this difference in semantics into
+ * account. Therefore, the meaning of chg is the same
+ * as in the shared case above. Code could easily be
+ * combined, but keeping it separate draws attention to
+ * subtle differences.
+ */
+ if (chg)
+ return false;
+ else
+ return true;
+ }
return false;
}
@@ -1011,6 +1030,7 @@ static void destroy_compound_gigantic_page(struct page *page,
int nr_pages = 1 << order;
struct page *p = page + 1;
+ atomic_set(compound_mapcount_ptr(page), 0);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
clear_compound_head(p);
set_page_refcounted(p);
@@ -1816,6 +1836,25 @@ static long __vma_reservation_common(struct hstate *h,
if (vma->vm_flags & VM_MAYSHARE)
return ret;
+ else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) && ret >= 0) {
+ /*
+ * In most cases, reserves always exist for private mappings.
+ * However, a file associated with mapping could have been
+ * hole punched or truncated after reserves were consumed.
+ * As subsequent fault on such a range will not use reserves.
+ * Subtle - The reserve map for private mappings has the
+ * opposite meaning than that of shared mappings. If NO
+ * entry is in the reserve map, it means a reservation exists.
+ * If an entry exists in the reserve map, it means the
+ * reservation has already been consumed. As a result, the
+ * return value of this routine is the opposite of the
+ * value returned from reserve map manipulation routines above.
+ */
+ if (ret)
+ return 0;
+ else
+ return 1;
+ }
else
return ret < 0 ? ret : 0;
}
@@ -4190,7 +4229,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (saddr) {
spte = huge_pte_offset(svma->vm_mm, saddr);
if (spte) {
- mm_inc_nr_pmds(mm);
get_page(virt_to_page(spte));
break;
}
@@ -4205,9 +4243,9 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (pud_none(*pud)) {
pud_populate(mm, pud,
(pmd_t *)((unsigned long)spte & PAGE_MASK));
+ mm_inc_nr_pmds(mm);
} else {
put_page(virt_to_page(spte));
- mm_inc_nr_pmds(mm);
}
spin_unlock(ptl);
out: