On Tue, Jul 24, 2012 at 12:23:58PM -0700, Hugh Dickins wrote: > On Tue, 24 Jul 2012, Mel Gorman wrote: > > On Mon, Jul 23, 2012 at 06:08:05PM -0700, Hugh Dickins wrote: > > > > > > So, after a bout of anxiety, I think my &= ~VM_MAYSHARE remains good. > > > > > > > I agree with you. When I was thinking about the potential problems, I was > > thinking of them in the general context of the core VM and what we normally > > take into account. > > > > I confess that I really find this working-by-coincidence very icky and am > > uncomfortable with it but your patch is the only patch that contains the > > mess to hugetlbfs. I fixed exit_mmap() for my version but only by changing > > the core to introduce exit_vmas() to take mmap_sem for write if a hugetlb > > VMA is found so I also affected the core. > > "icky" is not quite the word I'd use, but yes, it feels like you only > have to dislodge a stone somewhere at the other end of the kernel, > and the whole lot would come tumbling down. > > If I could think of a suitable VM_BUG_ON to insert next to the ~VM_MAYSHARE, > I would: to warn us when assumptions change. If we were prepared to waste > another vm_flag on it (and just because there's now a type which lets them > expand does not mean we can be profligate with them), then you can imagine > a VM_GOINGAWAY flag set in unmap_region() and exit_mmap(), and we key off > that instead; or something of that kind. > A new VM flag would be overkill for this right now. > But I'm afraid I see that as TODO-list material: the one-liner is pretty > good for stable backporting, and I felt smiled-upon when it turned out to > be workable (and not even needing a change in arch/x86/mm, that really > surprised me). It seems ungrateful not to seize the simple fix it offers, > which I found much easier to understand than the alternatives. > That's fair enough. > > > > So, lets go with your patch but with all this documented! I stuck a > > changelog and an additional comment onto your patch and this is the end > > result. > > Okay, thanks. (I think you've copied rather more of my previous mail > into the commit description than it deserves, but it looks like you > like more words where I like less!) > I did copy more than was necessary, I'll fix it. > > > > Do you want to pick this up and send it to Andrew or will I? > > Oh, please change your Reviewed-by to Signed-off-by: almost all of the > work and description comes from you and Michal; then please, you send it > in to Andrew - sorry, I really need to turn my attention to other things. > That's fine, I'll pick it. Thanks for working on this. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>