Messages in this thread | | | Date | Sat, 5 Dec 2009 12:37:00 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [PATCH] hugetlb: Acquire the i_mmap_lock before walking the prio_tree to unmap a page |
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On Wed, 2 Dec 2009, Mel Gorman wrote: > On Wed, Dec 02, 2009 at 10:16:02PM +0000, Mel Gorman wrote: > > On Wed, Dec 02, 2009 at 08:13:39PM +0000, Hugh Dickins wrote: > > > > > > But the comment seems wrong to me: hugetlb_instantiation_mutex > > > guards against concurrent hugetlb_fault()s; but the structure of > > > the prio_tree shifts as vmas based on that inode are inserted into > > > (mmap'ed) and removed from (munmap'ed) that tree (always while > > > holding i_mmap_lock). I don't see hugetlb_instantiation_mutex > > > giving us any protection against this at present. > > > > > > > You're right of course. I'll report without that nonsense included. > > > > Actually, shouldn't the mmap_sem be protecting against concurrent mmap and > munmap altering the tree? The comment is still bogus of course.
No, the mmap_sem can only protect against other threads sharing that same mm: whereas the prio_tree can shift around according to concurrent mmaps and munmaps of the same file in other mms.
Hugh
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