• Peter Zijlstra's avatar
    mm: mmu_gather rework · d16dfc55
    Peter Zijlstra authored
    Rework the existing mmu_gather infrastructure.
    
    The direct purpose of these patches was to allow preemptible mmu_gather,
    but even without that I think these patches provide an improvement to the
    status quo.
    
    The first 9 patches rework the mmu_gather infrastructure.  For review
    purpose I've split them into generic and per-arch patches with the last of
    those a generic cleanup.
    
    The next patch provides generic RCU page-table freeing, and the followup
    is a patch converting s390 to use this.  I've also got 4 patches from
    DaveM lined up (not included in this series) that uses this to implement
    gup_fast() for sparc64.
    
    Then there is one patch that extends the generic mmu_gather batching.
    
    After that follow the mm preemptibility patches, these make part of the mm
    a lot more preemptible.  It converts i_mmap_lock and anon_vma->lock to
    mutexes which together with the mmu_gather rework makes mmu_gather
    preemptible as well.
    
    Making i_mmap_lock a mutex also enables a clean-up of the truncate code.
    
    This also allows for preemptible mmu_notifiers, something that XPMEM I
    think wants.
    
    Furthermore, it removes the new and universially detested unmap_mutex.
    
    This patch:
    
    Remove the first obstacle towards a fully preemptible mmu_gather.
    
    The current scheme assumes mmu_gather is always done with preemption
    disabled and uses per-cpu storage for the page batches.  Change this to
    try and allocate a page for batching and in case of failure, use a small
    on-stack array to make some progress.
    
    Preemptible mmu_gather is desired in general and usable once i_mmap_lock
    becomes a mutex.  Doing it before the mutex conversion saves us from
    having to rework the code by moving the mmu_gather bits inside the
    pte_lock.
    
    Also avoid flushing the tlb batches from under the pte lock, this is
    useful even without the i_mmap_lock conversion as it significantly reduces
    pte lock hold times.
    
    [akpm@linux-foundation.org: fix comment tpyo]
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: David Miller <davem@davemloft.net>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Russell King <rmk@arm.linux.org.uk>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: Jeff Dike <jdike@addtoit.com>
    Cc: Richard Weinberger <richard@nod.at>
    Cc: Tony Luck <tony.luck@intel.com>
    Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Acked-by: default avatarHugh Dickins <hughd@google.com>
    Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Nick Piggin <npiggin@kernel.dk>
    Cc: Namhyung Kim <namhyung@gmail.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    d16dfc55
mmap.c 70 KB