Re: forcing write-back from FS - again

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 22 Oct 2007 12:38:48 +0300 Artem Bityutskiy <dedekind@yandex.ru> wrote:

> Andrew Morton wrote:
> >> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> >> @@ -28,6 +28,7 @@ static inline int task_is_pdflush(struct task_struct *task)
> >>    */
> >>   enum writeback_sync_modes {
> >>          WB_SYNC_NONE,   /* Don't wait on anything */
> >> +       WB_SYNC_NONE_PG,/* Don't wait on anything, don't touch locked pages */
> >>          WB_SYNC_ALL,    /* Wait on every mapping */
> >>          WB_SYNC_HOLD,   /* Hold the inode on sb_dirty for sys_sync() */
> >>   };
> > 
> > It would be simpler/safer/saner to add a new bitflag to writeback_control
> > and use that directly.  The WB_SYNC_foo flags are a holdover from an
> > earlier time and really should be made to go away, in favour of directly
> > setting up an appropriate writeback_control.
> 
> You mean something like (wbc->flags & WB_SYNC_NONE) etc? But below you used 
> wbc->skip_locked_pages, I'm confused.

take a look at struct writeback_control:

        unsigned nonblocking:1;         /* Don't get stuck on request queues */
        unsigned encountered_congestion:1; /* An output: a queue is full */
        unsigned for_kupdate:1;         /* A kupdate writeback */
        unsigned for_reclaim:1;         /* Invoked from the page allocator */
        unsigned for_writepages:1;      /* This is a writepages() call */
        unsigned range_cyclic:1;        /* range_start is cyclic */
        unsigned more_io:1;             /* more io to be dispatched */

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