diff options
| author | Mike Kravetz <mike.kravetz@oracle.com> | 2019-02-05 13:04:12 +1100 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2019-02-05 13:04:12 +1100 |
| commit | 87cd030ee6edc89554fb87c7894a90ee74d3f9a2 (patch) | |
| tree | 349e40bb9c02daba2df19f312a53f0d8323a1f94 /fs | |
| parent | d2c3aac7f989e1b2c643e616478192646f2848cb (diff) | |
| download | linux-next-87cd030ee6edc89554fb87c7894a90ee74d3f9a2.tar.gz | |
huegtlbfs: fix page leak during migration of file pages
Files can be created and mapped in an explicitly mounted hugetlbfs
filesystem. If pages in such files are migrated, the filesystem usage
will not be decremented for the associated pages. This can result in mmap
or page allocation failures as it appears there are fewer pages in the
filesystem than there should be.
For example, a test program which hole punches, faults and migrates pages
in such a file (1G in size) will eventually fail because it can not
allocate a page. Reported counts and usage at time of failure:
node0
537 free_hugepages
1024 nr_hugepages
0 surplus_hugepages
node1
1000 free_hugepages
1024 nr_hugepages
0 surplus_hugepages
Filesystem Size Used Avail Use% Mounted on
nodev 4.0G 4.0G 0 100% /var/opt/hugepool
Note that the filesystem shows 4G of pages used, while actual usage is 511
pages (just under 1G). Failed trying to allocate page 512.
If a hugetlb page is associated with an explicitly mounted filesystem,
this information in contained in the page_private field. At migration
time, this information is not preserved. To fix, simply transfer
page_private from old to new page at migration time if necessary. Also,
migrate_page_states() unconditionally clears page_private and PagePrivate
of the old page. It is unlikely, but possible that these fields could be
non-NULL and are needed at hugetlb free page time. So, do not touch these
fields for hugetlb pages.
Link: http://lkml.kernel.org/r/20190130211443.16678-1-mike.kravetz@oracle.com
Fixes: 290408d4a250 ("hugetlb: hugepage migration core")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/hugetlbfs/inode.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 32920a10100e..fb6de1db8806 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -859,6 +859,16 @@ static int hugetlbfs_migrate_page(struct address_space *mapping, rc = migrate_huge_page_move_mapping(mapping, newpage, page); if (rc != MIGRATEPAGE_SUCCESS) return rc; + + /* + * page_private is subpool pointer in hugetlb pages, transfer + * if needed. + */ + if (page_private(page) && !page_private(newpage)) { + set_page_private(newpage, page_private(page)); + set_page_private(page, 0); + } + if (mode != MIGRATE_SYNC_NO_COPY) migrate_page_copy(newpage, page); else |