Re: [Experimental][PATCH] putback_lru_page rework

[KOSAKI Motohiro]

> > Before:
> >       lock_page()(TestSetPageLocked())
> >       spin_lock(zone->lock)
> >       unlock_page()
> >       spin_unlock(zone->lock)  
> 
> Couple of comments:
> * I believe that the locks are acquired in the right order--at least as
> documented in the comments in mm/rmap.c.  
> * The unlocking appears out of order because this function attempts to
> hold the zone lock across a few pages in the pagevec, but must switch to
> a different zone lru lock when it finds a page on a different zone from
> the zone whose lock it is holding--like in the pagevec draining
> functions, altho' they don't need to lock the page.
> 
> > After:
> >       spin_lock(zone->lock)
> >       spin_unlock(zone->lock)
> 
> Right.  With your reworked check_move_unevictable_page() [with retry],
> we don't need to lock the page here, any more.  That means we can revert
> all of the changes to pass the mapping back to sys_shmctl() and move the
> call to scan_mapping_unevictable_pages() back to shmem_lock() after
> clearing the address_space's unevictable flag.  We only did that to
> avoid sleeping while holding the shmem_inode_info lock and the
> shmid_kernel's ipc_perm spinlock.  
> 
> Shall I handle that, after we've tested this patch?

Yeah, I'll do it :)


> > @@ -2438,7 +2437,7 @@ static void show_page_path(struct page *
> >   */
> >  static void check_move_unevictable_page(struct page *page, struct zone *zone)
> >  {
> > -
> > +retry:
> >  	ClearPageUnevictable(page); /* for page_evictable() */
> We can remove this comment            ^^^^^^^^^^^^^^^^^^^^^^^^^^
> page_evictable() no longer asserts !PageUnevictable(), right?

Yes.
I'll remove it.



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