• David Vrabel's avatar
    mm: sync vmalloc address space page tables in alloc_vm_area() · 461ae488
    David Vrabel authored
    Xen backend drivers (e.g., blkback and netback) would sometimes fail to
    map grant pages into the vmalloc address space allocated with
    alloc_vm_area().  The GNTTABOP_map_grant_ref would fail because Xen could
    not find the page (in the L2 table) containing the PTEs it needed to
    (XEN) mm.c:3846:d0 Could not find L1 PTE for address fbb42000
    netback and blkback were making the hypercall from a kernel thread where
    task->active_mm != &init_mm and alloc_vm_area() was only updating the page
    tables for init_mm.  The usual method of deferring the update to the page
    tables of other processes (i.e., after taking a fault) doesn't work as a
    fault cannot occur during the hypercall.
    This would work on some systems depending on what else was using vmalloc.
    Fix this by reverting ef691947 ("vmalloc: remove vmalloc_sync_all()
    from alloc_vm_area()") and add a comment to explain why it's needed.
    Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
    Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Ian Campbell <Ian.Campbell@citrix.com>
    Cc: Keir Fraser <keir.xen@gmail.com>
    Cc: <stable@kernel.org>		[3.0.x]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
vmalloc.c 64.2 KB