Messages in this thread | | | Date | Mon, 16 Oct 2000 11:29:27 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: mapping user space buffer to kernel address space |
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On Mon, 16 Oct 2000, Andrea Arcangeli wrote: > > I'm also not convinced that only increasing the page count in the critical > section in map_user_kiobuf is enough because swap_out doesn't care about the > page count (in 2.2.x rawio it's taking the page lock). The page count is > significant as a "pin" only for the page cache and not for anonymous or shm > memory for example.
The page count is (or should be) sufficient, and if it weren't sufficient that would be a bug in the swap-out handling of anonymous or shm memory. I refuse to see page locking or similar for this kind of pinning (counts are recursive and re-entrant, a "lock bit" is not).
Anonymous pages that get swapped out use the page cache too, so it's all safe (it's _not_ safe in 2.0.x or possibly even 2.2.x for shm, but 2.4.x should be ok - if it's not we need to fix it in the shm_swap function, not in the kiobuf code).
Linus
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