• Aneesh Kumar K.V's avatar
    powerpc/mmap: Any hint > 128TB searches the full VA space · 321f7d29
    Aneesh Kumar K.V authored
    As part of the new large address space support, processes start out life with a
    128TB virtual address space. However when calling mmap() a process can pass a
    hint address, and if that hint is > 128TB the kernel will use the full 512TB
    address space to try and satisfy the mmap() request.
    
    Currently we have a check that the hint is > 128TB and < 512TB (TASK_SIZE),
    which was added as an optimisation to avoid updating addr_limit unnecessarily
    and also to avoid calling slice_flush_segments() on all CPUs more than
    necessary.
    
    However this has the user-visible side effect that an mmap() hint above 512TB
    does not search the full address space unless a preceding mmap() used a hint
    value > 128TB && < 512TB.
    
    So fix it to treat any hint above 128TB as a hint to search the full address
    space, instead of checking the hint against TASK_SIZE, we instead check if the
    addr_limit is already == TASK_SIZE.
    
    This also brings the ABI in-line with what is proposed on x86. ie, that a hint
    address above 128TB up to and including (2^64)-1 is an indication to search the
    full address space.
    
    Fixes: f4ea6dcb (powerpc/mm: Enable mappings above 128TB)
    Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    321f7d29
mmap.c 6.08 KB