Re: [RFC, PATCH 0/2] mm: map few pages around fault address if they are in page cache

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Linus Torvalds wrote:
> On Tue, Feb 11, 2014 at 3:58 PM, Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> > Linus Torvalds wrote:
> >
> > It's on top of v3.14-rc1 + __do_fault() claen up[1].
> >
> > It's also on git:
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux fault_around/v1
> >
> > [1] http://thread.gmane.org/gmane.linux.kernel.mm/113364
> 
> Ok, that patch-series looks good to me too.
> 
> And I still see nothing wrong that would cause it not to boot.

It actually boot to UI and kinda work until I try to rebuild kernel.
Then all IO stops, but my window manager is still work. I can switch
between windows :-/

> I think the "do_async_mmap_readahead()" in lock_secondary_pages() is silly
> and shouldn't really be done, but I don't think it should cause any problems
> per se, it just feels very wrong to do that inside the loop.

I tried to replace do_async_mmap_readahead() locally with this:

diff --git a/mm/filemap.c b/mm/filemap.c
index 0661358db958..b28d19cafefc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1612,8 +1612,8 @@ static struct page *lock_secondary_pages(struct vm_area_struct *vma,
 		}
 		if (pages[i]->index > vmf->max)
 			goto put;
-		do_async_mmap_readahead(vma, &file->f_ra, file,
-				pages[i], pages[i]->index);
+		if (PageReadahead(pages[i]))
+			goto put;
 		if (!trylock_page(pages[i]))
 			goto put;
 		/* Truncated? */
@@ -1625,6 +1625,8 @@ static struct page *lock_secondary_pages(struct vm_area_struct *vma,
 			>> PAGE_CACHE_SHIFT;
 		if (unlikely(pages[i]->index >= size))
 			goto unlock;
+		if (file->f_ra.mmap_miss > 0)
+			file->f_ra.mmap_miss--;
 		continue;
 unlock:
 		unlock_page(pages[i]);
-- 
 Kirill A. Shutemov

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