Messages in this thread | | | Date | Wed, 6 Feb 2008 20:33:07 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [PATCH] sys_remap_file_pages: fix ->vm_file accounting |
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On Sun, 3 Feb 2008, Oleg Nesterov wrote: > > So I have to try to find another bug ;) Suppose that ->load_binary() does > a series of do_mmap(MAP_EXECUTABLE). It is possible that mmap_region() can > merge 2 vmas. In that case we "leak" ->num_exe_file_vmas. Unless I missed > something, mmap_region() should do removed_exe_file_vma() when vma_merge() > succeds (near fput(file)).
Or there's the complementary case of a VM_EXECUTABLE vma being split in two, for example by an mprotect of a part of it.
Sorry, Matt, I don't like your patch at all. It seems to add a fair amount of ugliness and unmaintainablity, all for a peculiar MVFS case (you've tried to argue other advantages, but not always convinced!).
And I found it quite hard to see where the crucial difference comes. I guess it's that MVFS changes vma->vm_file in its ->mmap? Well, if MVFS does that, maybe something else does that too, but precisely to rely on the present behaviour of /proc/pid/exe - so in fixing for MVFS, we'd be breaking that hypothetical other?
I can understand patches to avoid mmap_sem for /proc/pid/exe, but this one just seems too messy for too special an out-of-tree case. (I've no last word on this, but that's my opinion.)
Hugh
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