Messages in this thread | | | Date | Sun, 10 Oct 1999 23:31:07 +0200 | From | Manfred Spraul <> | Subject | Re: locking question: do_mmap(), do_munmap() |
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Alexander Viro wrote: > Hold on. In swap_out_mm() you have to protect find_vma() (OK, it doesn't > block, but we'll have to take care of mm->mmap_cache) _and_ you'll have to > protect vma from destruction all way down to try_to_swap_out(). And to > vma->swapout(). Which can sleep, so spinlocks are out of question here.
I found vma->swapout() when I tried to implement it. Sh... We could make vma_list_lock a semaphore, but I haven't checked for any hidden problems yet.
> > I still think that just keeping a cyclic list of pages, grabbing from that > list before taking mmap_sem _if_ we have a chance for blocking > __get_free_page(), refilling if the list is empty (prior to down()) and > returning the page into the list if we didn't use it may be the simplest > way.
I don't like the idea, but it sounds possible. A problem could be that the page-in functions can allocate memory: do_nopage() -> filemap_nopage(): it calls i_op->readpage() which would call get_block(), eg ext2: load the indirect page, this needs memory --> OOM.
-- Manfred
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