This is a note to let you know that I've just added the patch titled
mm/hugetlbfs: fix bugs in fallocate hole punch of areas with holes
to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-hugetlbfs-fix-bugs-in-fallocate-hole-punch-of-areas-with-holes.patch
and it can be found in the queue-4.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1817889e3b2cc1db8abb595712095129ff9156c1 Mon Sep 17 00:00:00 2001
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Date: Fri, 20 Nov 2015 15:57:13 -0800
Subject: mm/hugetlbfs: fix bugs in fallocate hole punch of areas with holes
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
commit 1817889e3b2cc1db8abb595712095129ff9156c1 upstream.
Hugh Dickins pointed out problems with the new hugetlbfs fallocate hole
punch code. These problems are in the routine remove_inode_hugepages and
mostly occur in the case where there are holes in the range of pages to be
removed. These holes could be the result of a previous hole punch or
simply sparse allocation. The current code could access pages outside the
specified range.
remove_inode_hugepages handles both hole punch and truncate operations.
Page index handling was fixed/cleaned up so that the loop index always
matches the page being processed. The code now only makes a single pass
through the range of pages as it was determined page faults could not race
with truncate. A cond_resched() was added after removing up to
PAGEVEC_SIZE pages.
Some totally unnecessary code in hugetlbfs_fallocate() that remained from
early development was also removed.
Tested with fallocate tests submitted here:
http://librelist.com/browser//libhugetlbfs/2015/6/25/patch-tests-add-tests-for-fallocate-system-call/
And, some ftruncate tests under development
Fixes: b5cec28d36f5 ("hugetlbfs: truncate_hugepages() takes a range of pages")
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: "Hillf Danton" <hillf.zj@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/hugetlbfs/inode.c | 65 +++++++++++++++++++++++++--------------------------
1 file changed, 32 insertions(+), 33 deletions(-)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -332,12 +332,17 @@ static void remove_huge_page(struct page
* 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
- * maps and global counts.
+ * maps and global counts. Page faults can not race with truncation
+ * in this routine. hugetlb_no_page() prevents page faults in the
+ * truncated range. It checks i_size before allocation, and again after
+ * with the page table lock for the page held. The same lock must be
+ * acquired to unmap a page.
* hole punch is indicated if end is not LLONG_MAX
* In the hole punch case we scan the range and release found pages.
* Only when releasing a page is the associated region/reserv map
* deleted. The region/reserv map for ranges without associated
- * pages are not modified.
+ * pages are not modified. Page faults can race with hole punch.
+ * This is indicated if we find a mapped page.
* Note: If the passed end of range value is beyond the end of file, but
* not LLONG_MAX this routine still performs a hole punch operation.
*/
@@ -361,46 +366,37 @@ static void remove_inode_hugepages(struc
next = start;
while (next < end) {
/*
- * Make sure to never grab more pages that we
- * might possibly need.
+ * Don't grab more pages than the number left in the range.
*/
if (end - next < lookup_nr)
lookup_nr = end - next;
/*
- * This pagevec_lookup() may return pages past 'end',
- * so we must check for page->index > end.
+ * When no more pages are found, we are done.
*/
- if (!pagevec_lookup(&pvec, mapping, next, lookup_nr)) {
- if (next == start)
- break;
- next = start;
- continue;
- }
+ if (!pagevec_lookup(&pvec, mapping, next, lookup_nr))
+ break;
for (i = 0; i < pagevec_count(&pvec); ++i) {
struct page *page = pvec.pages[i];
u32 hash;
+ /*
+ * The page (index) could be beyond end. This is
+ * only possible in the punch hole case as end is
+ * max page offset in the truncate case.
+ */
+ next = page->index;
+ if (next >= end)
+ break;
+
hash = hugetlb_fault_mutex_hash(h, current->mm,
&pseudo_vma,
mapping, next, 0);
mutex_lock(&hugetlb_fault_mutex_table[hash]);
lock_page(page);
- if (page->index >= end) {
- unlock_page(page);
- mutex_unlock(&hugetlb_fault_mutex_table[hash]);
- next = end; /* we are done */
- break;
- }
-
- /*
- * 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.
- */
- if (!page_mapped(page)) {
+ if (likely(!page_mapped(page))) {
bool rsv_on_error = !PagePrivate(page);
/*
* We must free the huge page and remove
@@ -421,17 +417,23 @@ static void remove_inode_hugepages(struc
hugetlb_fix_reserve_counts(
inode, rsv_on_error);
}
+ } else {
+ /*
+ * If page is mapped, it was faulted in after
+ * being unmapped. It indicates a race between
+ * hole punch and page fault. Do nothing in
+ * this case. Getting here in a truncate
+ * operation is a bug.
+ */
+ BUG_ON(truncate_op);
}
- if (page->index > next)
- next = page->index;
-
- ++next;
unlock_page(page);
-
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
}
+ ++next;
huge_pagevec_release(&pvec);
+ cond_resched();
}
if (truncate_op)
@@ -647,9 +649,6 @@ static long hugetlbfs_fallocate(struct f
if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
i_size_write(inode, offset + len);
inode->i_ctime = CURRENT_TIME;
- spin_lock(&inode->i_lock);
- inode->i_private = NULL;
- spin_unlock(&inode->i_lock);
out:
mutex_unlock(&inode->i_mutex);
return error;
Patches currently in stable-queue which might be from mike.kravetz@xxxxxxxxxx are
queue-4.3/mm-hugetlb-call-huge_pte_alloc-only-if-ptep-is-null.patch
queue-4.3/mm-hugetlbfs-fix-bugs-in-fallocate-hole-punch-of-areas-with-holes.patch
queue-4.3/mm-hugetlb.c-fix-resv-map-memory-leak-for-placeholder-entries.patch
queue-4.3/mm-hugetlb-fix-hugepage-memory-leak-caused-by-wrong-reserve-count.patch
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