On Fri, 13 Jun 2014, David Herrmann wrote: > We currently fail setting SEAL_WRITE in case there're pending page > references. This patch extends the pin-tests to wait up to 150ms for all > references to be dropped. This is still not perfect in that it doesn't > account for harmless read-only pins, but it's much better than a hard > failure. > > Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx> Right, I didn't look through the patch itself, just compared the result with what I sent. Okay, you prefer to separate out shmem_tag_pins(). Yes, it looks fine. There's just one change I'd like at this stage, something I realized shortly after sending the code fragment: please add a call to lru_add_drain() at the head of shmem_tag_pins(). The reason being that lru_add_drain() is local to the cpu, so cheap, and in many cases will bring down all the raised refcounts right then. Whereas lru_add_drain_all() in the first scan of shmem_wait_for_pins() is much more expensive, involving inter-processor interrupts to do that on all cpus: it is appropriate to call it at that point, but we really ought to try the cheaper lru_add_drain() at the earlier stage. I would also like never to embark on this scan of the radix_tree and wait for pins, if the pages were never given out in a VM_SHARED mapping - or is that unrealistic, because every memfd is read-write, and typical initialization expected to be by mmap() rather than write()? But anyway, you're quite right not to get into that at this stage: it's best left as an optimization once the basics are safely in. Hugh -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
