Messages in this thread | | | Date | Wed, 7 Mar 2007 08:25:46 +0100 | From | Nick Piggin <> | Subject | Re: [patch 3/6] mm: fix fault vs invalidate race for linear mappings |
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On Tue, Mar 06, 2007 at 11:08:41PM -0800, Andrew Morton wrote: > On Wed, 7 Mar 2007 07:57:27 +0100 Nick Piggin <npiggin@suse.de> wrote: > > > > > > > Why was truncate_inode_pages_range() altered to unmap the page if it got > > > mapped again? > > > > > > Oh. Because the unmap_mapping_range() call got removed from vmtruncate(). > > > Why? (Please send suitable updates to the changelog). > > > > We have to ensure it is unmapped, and be prepared to unmap it while under > > the page lock. > > But vmtruncate() dropped i_size, so nobody will map this page into > pagetables from then on.
But there could be a fault in progress... the only way to know is locking the page.
> > > I guess truncate of a mmapped area isn't sufficiently common to worry about > > > the inefficiency of this change. > > > > Yeah, and it should be more efficient for files that aren't mmapped, > > because we don't have to take i_mmap_lock for them. > > > > > Lots of memory barriers got removed in memory.c, unchangeloggedly. > > > > Yeah they were all for the lockless truncate_count checks. Now that > > we use the page lock, we don't need barriers. > > > > > Gratuitous renaming of locals in do_no_page() makes the change hard to > > > review. Should have been a separate patch. > > > > > > In fact, the patch would have been heaps clearer if that renaming had been > > > a separate patch. > > > > Shall I? > > If you don't have anything better to do, yes please ;)
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