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Date: Tue, 20 Oct 2015 16:52:22 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Hugh Dickins <hughd@...gle.com>,
Davidlohr Bueso <dave@...olabs.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH v2 4/4] mm/hugetlb: Unmap pages to remove if page fault raced with hole punch
Page faults can race with fallocate hole punch. If a page fault happens
between the unmap and remove operations, the page is not removed and
remains within the hole. This is not the desired behavior. If a page
is mapped, the remove operation (remove_inode_hugepages) will unmap the
page before removing. The unmap within remove_inode_hugepages occurs
with the hugetlb_fault_mutex held so that no other faults can occur
until the page is removed.
The (unmodified) routine hugetlb_vmdelete_list was moved ahead of
remove_inode_hugepages to satisfy the new reference.
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
fs/hugetlbfs/inode.c | 123 ++++++++++++++++++++++++++-------------------------
1 file changed, 63 insertions(+), 60 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 719bbe0..f25b72f 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -324,11 +324,44 @@ static void remove_huge_page(struct page *page)
delete_from_page_cache(page);
}
+static inline void
+hugetlb_vmdelete_list(struct rb_root *root, pgoff_t start, pgoff_t end)
+{
+ struct vm_area_struct *vma;
+
+ /*
+ * end == 0 indicates that the entire range after
+ * start should be unmapped.
+ */
+ vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
+ unsigned long v_offset;
+
+ /*
+ * Can the expression below overflow on 32-bit arches?
+ * No, because the interval tree returns us only those vmas
+ * which overlap the truncated area starting at pgoff,
+ * and no vma on a 32-bit arch can span beyond the 4GB.
+ */
+ if (vma->vm_pgoff < start)
+ v_offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
+ else
+ v_offset = 0;
+
+ if (end) {
+ end = ((end - start) << PAGE_SHIFT) +
+ vma->vm_start + v_offset;
+ if (end > vma->vm_end)
+ end = vma->vm_end;
+ } else
+ end = vma->vm_end;
+
+ unmap_hugepage_range(vma, vma->vm_start + v_offset, end, NULL);
+ }
+}
/*
* remove_inode_hugepages handles two distinct cases: truncation and hole
* punch. There are subtle differences in operation for each case.
-
* truncation is indicated by end of range being LLONG_MAX
* In this case, we first scan the range and release found pages.
* After releasing pages, hugetlb_unreserve_pages cleans up region/reserv
@@ -381,12 +414,25 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
for (i = 0; i < pagevec_count(&pvec); ++i) {
struct page *page = pvec.pages[i];
u32 hash;
+ bool rsv_on_error;
hash = hugetlb_fault_mutex_hash(h, current->mm,
&pseudo_vma,
mapping, next, 0);
mutex_lock(&hugetlb_fault_mutex_table[hash]);
+ /*
+ * If page is mapped, it was faulted in after being
+ * unmapped in caller. Unmap (again) now after taking
+ * the fault mutex. The mutex will prevent faults
+ * until we finish removing the page.
+ */
+ if (page_mapped(page)) {
+ hugetlb_vmdelete_list(&mapping->i_mmap,
+ next * pages_per_huge_page(h),
+ (next + 1) * pages_per_huge_page(h));
+ }
+
lock_page(page);
if (page->index >= end) {
unlock_page(page);
@@ -396,31 +442,23 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
}
/*
- * If page is mapped, it was faulted in after being
- * unmapped. Do nothing in this race case. In the
- * normal case page is not mapped.
+ * We must free the huge page and remove from page
+ * cache (remove_huge_page) BEFORE removing the
+ * region/reserve map (hugetlb_unreserve_pages).
+ * In rare out of memory conditions, removal of the
+ * region/reserve map could fail. Before free'ing
+ * the page, note PagePrivate which is used in case
+ * of error.
*/
- if (!page_mapped(page)) {
- bool rsv_on_error = !PagePrivate(page);
- /*
- * We must free the huge page and remove
- * from page cache (remove_huge_page) BEFORE
- * removing the region/reserve map
- * (hugetlb_unreserve_pages). In rare out
- * of memory conditions, removal of the
- * region/reserve map could fail. Before
- * free'ing the page, note PagePrivate which
- * is used in case of error.
- */
- remove_huge_page(page);
- freed++;
- if (!truncate_op) {
- if (unlikely(hugetlb_unreserve_pages(
- inode, next,
- next + 1, 1)))
- hugetlb_fix_reserve_counts(
- inode, rsv_on_error);
- }
+ rsv_on_error = !PagePrivate(page);
+ remove_huge_page(page);
+ freed++;
+ if (!truncate_op) {
+ if (unlikely(hugetlb_unreserve_pages(inode,
+ next, next + 1,
+ 1)))
+ hugetlb_fix_reserve_counts(inode,
+ rsv_on_error);
}
if (page->index > next)
@@ -450,41 +488,6 @@ static void hugetlbfs_evict_inode(struct inode *inode)
clear_inode(inode);
}
-static inline void
-hugetlb_vmdelete_list(struct rb_root *root, pgoff_t start, pgoff_t end)
-{
- struct vm_area_struct *vma;
-
- /*
- * end == 0 indicates that the entire range after
- * start should be unmapped.
- */
- vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
- unsigned long v_offset;
-
- /*
- * Can the expression below overflow on 32-bit arches?
- * No, because the interval tree returns us only those vmas
- * which overlap the truncated area starting at pgoff,
- * and no vma on a 32-bit arch can span beyond the 4GB.
- */
- if (vma->vm_pgoff < start)
- v_offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
- else
- v_offset = 0;
-
- if (end) {
- end = ((end - start) << PAGE_SHIFT) +
- vma->vm_start + v_offset;
- if (end > vma->vm_end)
- end = vma->vm_end;
- } else
- end = vma->vm_end;
-
- unmap_hugepage_range(vma, vma->vm_start + v_offset, end, NULL);
- }
-}
-
static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
pgoff_t pgoff;
--
2.4.3
--
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