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mm/hugetlbfs: fix bugs in fallocate hole punch of areas with holes 

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: b5cec28d36 ("hugetlbfs: truncate_hugepages() takes a range of pages")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Hillf Danton" <hillf.zj@alibaba-inc.com>
Cc: <stable@vger.kernel.org>	[4.3]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Kravetz 2015-11-20 15:57:13 -08:00 committed by Linus Torvalds
parent 50e55bf626
commit 1817889e3b
1 changed files with 32 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
fs/hugetlbfs/inode.c
View File

@ -332,12 +332,17 @@ static void remove_huge_page(struct page *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(struct inode *inode, loff_t lstart,
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(struct inode *inode, loff_t lstart,
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 file *file, int mode, loff_t offset,
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;