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    Subjectiput() in reclaim context
    On Tue, 20 May 2008, Andrew Morton wrote:
    > On Wed, 21 May 2008 10:15:32 +0400 Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
    > > On Tue, May 20, 2008 at 04:28:16PM -0700, Andrew Morton (akpm@linux-foundation.org) wrote:
    > > > It's more than efficiency. There are lots and lots of things we cannot
    > > > do in direct-reclaim context.
    > > >
    > > > ...
    > > >
    > > > c) Cannot run iput(). Or at least, we couldn't five or six years
    > > > ago. afaik nobody has investigated whether the situation is now
    > > > better or worse.

    I happened to notice your remark in the buffer heads defrag thread.
    Do you remember what that limitation was about?

    Because just a few months ago I discovered a shmem race which I fixed
    by doing igrab+iput in shmem_writepage, in the reclaim context. Feeling
    guilty now: I'd better investigate, but would welcome a starting pointer.

    (If I'm lucky, it'll be that the generic code in vmscan.c cannot
    use iput, but particular filesystems might themselves be safe to.)

    Thanks,
    Hugh


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