• Minchan Kim's avatar
    mm/madvise: pass mm to do_madvise · 0726b01e
    Minchan Kim authored
    Patch series "introduce memory hinting API for external process", v9.
    
    Now, we have MADV_PAGEOUT and MADV_COLD as madvise hinting API.  With
    that, application could give hints to kernel what memory range are
    preferred to be reclaimed.  However, in some platform(e.g., Android), the
    information required to make the hinting decision is not known to the app.
    Instead, it is known to a centralized userspace daemon(e.g.,
    ActivityManagerService), and that daemon must be able to initiate reclaim
    on its own without any app involvement.
    
    To solve the concern, this patch introduces new syscall -
    process_madvise(2).  Bascially, it's same with madvise(2) syscall but it
    has some differences.
    
    1. It needs pidfd of target process to provide the hint
    
    2. It supports only MADV_{COLD|PAGEOUT|MERGEABLE|UNMEREABLE} at this
       moment.  Other hints in madvise will be opened when there are explicit
       requests from community to prevent unexpected bugs we couldn't support.
    
    3. Only privileged processes can do something for other process's
       address space.
    
    For more detail of the new API, please see "mm: introduce external memory
    hinting API" description in this patchset.
    
    This patch (of 3):
    
    In upcoming patches, do_madvise will be called from external process
    context so we shouldn't asssume "current" is always hinted process's
    task_struct.
    
    Furthermore, we must not access mm_struct via task->mm, but obtain it via
    access_mm() once (in the following patch) and only use that pointer [1],
    so pass it to do_madvise() as well.  Note the vma->vm_mm pointers are
    safe, so we can use them further down the call stack.
    
    And let's pass current->mm as arguments of do_madvise so it shouldn't
    change existing behavior but prepare next patch to make review easy.
    
    [vbabka@suse.cz: changelog tweak]
    [minchan@kernel.org: use current->mm for io_uring]
      Link: http://lkml.kernel.org/r/20200423145215.72666-1-minchan@kernel.org
    [akpm@linux-foundation.org: fix it for upstream changes]
    [akpm@linux-foundation.org: whoops]
    [rdunlap@infradead.org: add missing includes]
    Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
    Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Acked-by: default avatarDavid Rientjes <rientjes@google.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Jann Horn <jannh@google.com>
    Cc: Tim Murray <timmurray@google.com>
    Cc: Daniel Colascione <dancol@google.com>
    Cc: Sandeep Patil <sspatil@google.com>
    Cc: Sonny Rao <sonnyrao@google.com>
    Cc: Brian Geffon <bgeffon@google.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Shakeel Butt <shakeelb@google.com>
    Cc: John Dias <joaodias@google.com>
    Cc: Joel Fernandes <joel@joelfernandes.org>
    Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
    Cc: SeongJae Park <sj38.park@gmail.com>
    Cc: Christian Brauner <christian@brauner.io>
    Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
    Cc: Oleksandr Natalenko <oleksandr@redhat.com>
    Cc: SeongJae Park <sjpark@amazon.de>
    Cc: Christian Brauner <christian.brauner@ubuntu.com>
    Cc: Florian Weimer <fw@deneb.enyo.de>
    Cc: <linux-man@vger.kernel.org>
    Link: https://lkml.kernel.org/r/20200901000633.1920247-1-minchan@kernel.org
    Link: http://lkml.kernel.org/r/20200622192900.22757-1-minchan@kernel.org
    Link: http://lkml.kernel.org/r/20200302193630.68771-2-minchan@kernel.org
    Link: http://lkml.kernel.org/r/20200622192900.22757-2-minchan@kernel.org
    Link: https://lkml.kernel.org/r/20200901000633.1920247-2-minchan@kernel.orgSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    0726b01e
io_uring.c 230 KB