Mike Kravetz c20f6d01ea hugetlb: use same fault hash key for shared and private mappings ... commit 1b426bac66 upstream. hugetlb uses a fault mutex hash table to prevent page faults of the same pages concurrently. The key for shared and private mappings is different. Shared keys off address_space and file index. Private keys off mm and virtual address. Consider a private mappings of a populated hugetlbfs file. A fault will map the page from the file and if needed do a COW to map a writable page. Hugetlbfs hole punch uses the fault mutex to prevent mappings of file pages. It uses the address_space file index key. However, private mappings will use a different key and could race with this code to map the file page. This causes problems (BUG) for the page cache remove code as it expects the page to be unmapped. A sample stack is: page dumped because: VM_BUG_ON_PAGE(page_mapped(page)) kernel BUG at mm/filemap.c:169! ... RIP: 0010:unaccount_page_cache_page+0x1b8/0x200 ... Call Trace: __delete_from_page_cache+0x39/0x220 delete_from_page_cache+0x45/0x70 remove_inode_hugepages+0x13c/0x380 ? __add_to_page_cache_locked+0x162/0x380 hugetlbfs_fallocate+0x403/0x540 ? _cond_resched+0x15/0x30 ? __inode_security_revalidate+0x5d/0x70 ? selinux_file_permission+0x100/0x130 vfs_fallocate+0x13f/0x270 ksys_fallocate+0x3c/0x80 __x64_sys_fallocate+0x1a/0x20 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 There seems to be another potential COW issue/race with this approach of different private and shared keys as noted in commit 8382d914eb ("mm, hugetlb: improve page-fault scalability"). Since every hugetlb mapping (even anon and private) is actually a file mapping, just use the address_space index key for all mappings. This results in potentially more hash collisions. However, this should not be the common case. Link: http://lkml.kernel.org/r/20190328234704.27083-3-mike.kravetz@oracle.com Link: http://lkml.kernel.org/r/20190412165235.t4sscoujczfhuiyt@linux-r8p5 Fixes: b5cec28d36 ("hugetlbfs: truncate_hugepages() takes a range of pages") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2019-05-31 06:47:12 -07:00
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Makefile	…
inode.c	hugetlb: use same fault hash key for shared and private mappings	2019-05-31 06:47:12 -07:00