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Use the non atomic version of __SetPageUptodate while the page is still private and not visible to lookup operations. Using the non atomic version after the page is already visible to lookups is unsafe as there would be concurrent lock_page operation modifying the page->flags while it runs. This solves a lockup in find_lock_entry with the userfaultfd_shmem selftest. userfaultfd_shm D14296 691 1 0x00000004 Call Trace: schedule+0x3d/0x90 schedule_timeout+0x228/0x420 io_schedule_timeout+0xa4/0x110 __lock_page+0x12d/0x170 find_lock_entry+0xa4/0x190 shmem_getpage_gfp+0xb9/0xc30 shmem_fault+0x70/0x1c0 __do_fault+0x21/0x150 handle_mm_fault+0xec9/0x1490 __do_page_fault+0x20d/0x520 trace_do_page_fault+0x61/0x270 do_async_page_fault+0x19/0x80 async_page_fault+0x25/0x30 Link: http://lkml.kernel.org/r/20170116180408.12184-2-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.