The patch titled Subject: huegtlbfs: fix page leak during migration of file pages has been added to the -mm tree. Its filename is huegtlbfs-fix-page-leak-during-migration-of-file-pages.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/huegtlbfs-fix-page-leak-during-migr... and later at http://ozlabs.org/~akpm/mmotm/broken-out/huegtlbfs-fix-page-leak-during-migr...
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------------------------------------------------------ From: Mike Kravetz mike.kravetz@oracle.com Subject: 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 ---
fs/hugetlbfs/inode.c | 10 ++++++++++ mm/migrate.c | 10 ++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)
--- a/fs/hugetlbfs/inode.c~huegtlbfs-fix-page-leak-during-migration-of-file-pages +++ a/fs/hugetlbfs/inode.c @@ -859,6 +859,16 @@ static int hugetlbfs_migrate_page(struct 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 --- a/mm/migrate.c~huegtlbfs-fix-page-leak-during-migration-of-file-pages +++ a/mm/migrate.c @@ -641,8 +641,14 @@ void migrate_page_states(struct page *ne */ if (PageSwapCache(page)) ClearPageSwapCache(page); - ClearPagePrivate(page); - set_page_private(page, 0); + /* + * Unlikely, but PagePrivate and page_private could potentially + * contain information needed at hugetlb free page time. + */ + if (!PageHuge(page)) { + ClearPagePrivate(page); + set_page_private(page, 0); + }
/* * If any waiters have accumulated on the new page then _
Patches currently in -mm which might be from mike.kravetz@oracle.com are
huegtlbfs-fix-page-leak-during-migration-of-file-pages.patch