When creating a hugetlb mapping, attempt PUD_SIZE alignment if the
following conditions are met:
- Address passed to mmap or shmat is NULL
- The mapping is flaged as shared
- The mapping is at least PUD_SIZE in length
If a PUD_SIZE aligned mapping can not be created, then fall back to a
huge page size mapping.
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
fs/hugetlbfs/inode.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 540ddc9..22b2e38 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -175,6 +175,17 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
struct vm_area_struct *vma;
struct hstate *h = hstate_file(file);
struct vm_unmapped_area_info info;
+ bool pud_size_align = false;
+ unsigned long ret_addr;
+
+ /*
+ * If PMD sharing is enabled, align to PUD_SIZE to facilitate
+ * sharing. Only attempt alignment if no address was passed in,
+ * flags indicate sharing and size is big enough.
+ */
+ if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
+ !addr && flags & MAP_SHARED && len >= PUD_SIZE)
+ pud_size_align = true;
if (len & ~huge_page_mask(h))
return -EINVAL;
@@ -199,9 +210,23 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
info.length = len;
info.low_limit = TASK_UNMAPPED_BASE;
info.high_limit = TASK_SIZE;
- info.align_mask = PAGE_MASK & ~huge_page_mask(h);
+ if (pud_size_align)
+ info.align_mask = PAGE_MASK & (PUD_SIZE - 1);
+ else
+ info.align_mask = PAGE_MASK & ~huge_page_mask(h);
info.align_offset = 0;
- return vm_unmapped_area(&info);
+ ret_addr = vm_unmapped_area(&info);
+
+ /*
+ * If failed with PUD_SIZE alignment, try again with huge page
+ * size alignment.
+ */
+ if ((ret_addr & ~PAGE_MASK) && pud_size_align) {
+ info.align_mask = PAGE_MASK & ~huge_page_mask(h);
+ ret_addr = vm_unmapped_area(&info);
+ }
+
+ return ret_addr;
}
#endif
--
2.4.3
--
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