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Date: Mon, 6 Jun 2016 10:45:28 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Hillf Danton <hillf.zj@...baba-inc.com>,
Michal Hocko <mhocko@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>
Subject: [RFC PATCH 3/6] mm/userfaultfd: add __mcopy_atomic_hugetlb for huge page UFFDIO_COPY
__mcopy_atomic_hugetlb performs the UFFDIO_COPY operation for huge
pages. It is based on the existing __mcopy_atomic routine for normal
pages. Unlike normal pages, there is no huge page support for the
UFFDIO_ZEROPAGE operation.
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
mm/userfaultfd.c | 179 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 179 insertions(+)
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index af817e5..c006f46 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -14,6 +14,8 @@
#include <linux/swapops.h>
#include <linux/userfaultfd_k.h>
#include <linux/mmu_notifier.h>
+#include <linux/hugetlb.h>
+#include <linux/pagemap.h>
#include <asm/tlbflush.h>
#include "internal.h"
@@ -139,6 +141,176 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
return pmd;
}
+
+#ifdef CONFIG_HUGETLB_PAGE
+/*
+ * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is
+ * called with mmap_sem held, it will release mmap_sem before returning.
+ */
+static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_start,
+ unsigned long src_start,
+ unsigned long len,
+ bool zeropage)
+{
+ ssize_t err;
+ pte_t *dst_pte;
+ unsigned long src_addr, dst_addr;
+ long copied;
+ struct page *page;
+ struct hstate *h;
+ unsigned long vma_hpagesize;
+ pgoff_t idx;
+ u32 hash;
+ struct address_space *mapping;
+
+ /*
+ * There is no default zero huge page for all huge page sizes as
+ * supported by hugetlb. A PMD_SIZE huge pages may exist as used
+ * by THP. Since we can not reliably insert a zero page, this
+ * feature is not supported.
+ */
+ if (zeropage)
+ return -EINVAL;
+
+ src_addr = src_start;
+ dst_addr = dst_start;
+ copied = 0;
+ page = NULL;
+ vma_hpagesize = vma_kernel_pagesize(dst_vma);
+
+retry:
+ /*
+ * On routine entry dst_vma is set. If we had to drop mmap_sem and
+ * retry, dst_vma will be set to NULL and we must lookup again.
+ */
+ err = -EINVAL;
+ if (!dst_vma) {
+ dst_vma = find_vma(dst_mm, dst_start);
+ vma_hpagesize = vma_kernel_pagesize(dst_vma);
+
+ /*
+ * Make sure the vma is not shared, that the dst range is
+ * both valid and fully within a single existing vma.
+ */
+ if (dst_vma->vm_flags & VM_SHARED)
+ goto out_unlock;
+ if (dst_start < dst_vma->vm_start ||
+ dst_start + len > dst_vma->vm_end)
+ goto out_unlock;
+ }
+
+ /*
+ * Validate alignment based on huge page size
+ */
+ if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
+ goto out_unlock;
+
+ /*
+ * Only allow __mcopy_atomic_hugetlb on userfaultfd registered ranges.
+ */
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
+ goto out_unlock;
+
+ /*
+ * Ensure the dst_vma has a anon_vma.
+ */
+ err = -ENOMEM;
+ if (unlikely(anon_vma_prepare(dst_vma)))
+ goto out_unlock;
+
+ h = hstate_vma(dst_vma);
+
+ while (src_addr < src_start + len) {
+ pte_t dst_pteval;
+
+ BUG_ON(dst_addr >= dst_start + len);
+ dst_addr &= huge_page_mask(h);
+
+ /*
+ * Serialize via hugetlb_fault_mutex
+ */
+ idx = linear_page_index(dst_vma, dst_addr);
+ mapping = dst_vma->vm_file->f_mapping;
+ hash = hugetlb_fault_mutex_hash(h, dst_mm, dst_vma, mapping,
+ idx, dst_addr);
+ mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
+ err = -ENOMEM;
+ dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
+ if (!dst_pte) {
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ goto out_unlock;
+ }
+
+ err = -EEXIST;
+ dst_pteval = huge_ptep_get(dst_pte);
+ if (!huge_pte_none(dst_pteval)) {
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ goto out_unlock;
+ }
+
+ err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
+ dst_addr, src_addr, &page);
+
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+
+ cond_resched();
+
+ if (unlikely(err == -EFAULT)) {
+ up_read(&dst_mm->mmap_sem);
+ BUG_ON(!page);
+
+ err = copy_huge_page_from_user(
+ (const void __user *)src_addr,
+ page, pages_per_huge_page(h));
+ if (unlikely(err)) {
+ err = -EFAULT;
+ goto out;
+ }
+ down_read(&dst_mm->mmap_sem);
+
+ dst_vma = NULL;
+ goto retry;
+ } else
+ BUG_ON(page);
+
+ if (!err) {
+ dst_addr += vma_hpagesize;
+ src_addr += vma_hpagesize;
+ copied += vma_hpagesize;
+
+ if (fatal_signal_pending(current))
+ err = -EINTR;
+ }
+ if (err)
+ break;
+ }
+
+out_unlock:
+ up_read(&dst_mm->mmap_sem);
+out:
+ if (page)
+ put_page(page);
+ BUG_ON(copied < 0);
+ BUG_ON(err > 0);
+ BUG_ON(!copied && !err);
+ return copied ? copied : err;
+}
+#else /* !CONFIG_HUGETLB_PAGE */
+static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_start,
+ unsigned long src_start,
+ unsigned long len,
+ bool zeropage)
+{
+ up_read(&dst_mm->mmap_sem); /* HUGETLB not configured */
+ BUG();
+}
+#endif /* CONFIG_HUGETLB_PAGE */
+
static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
unsigned long dst_start,
unsigned long src_start,
@@ -182,6 +354,13 @@ retry:
goto out_unlock;
/*
+ * If this is a HUGETLB vma, pass off to appropriate routine
+ */
+ if (dst_vma->vm_flags & VM_HUGETLB)
+ return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
+ src_start, len, false);
+
+ /*
* Be strict and only allow __mcopy_atomic on userfaultfd
* registered ranges to prevent userland errors going
* unnoticed. As far as the VM consistency is concerned, it
--
2.4.11
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