Messages in this thread | | | From | "Huang, Ying" <> | Subject | Re: [PATCH] mm,shmem: Fix a typo in shmem_swapin_page() | Date | Tue, 10 Aug 2021 07:43:46 +0800 |
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Yang Shi <shy828301@gmail.com> writes:
> On Fri, Aug 6, 2021 at 1:37 PM Yang Shi <shy828301@gmail.com> wrote: >> >> On Thu, Aug 5, 2021 at 11:01 PM Hugh Dickins <hughd@google.com> wrote: >> > >> > On Thu, 5 Aug 2021, Yang Shi wrote: >> > > On Tue, Aug 3, 2021 at 10:34 PM Hugh Dickins <hughd@google.com> wrote: >> > > > >> > > > I've never seen the swapoff race claimed by Miaohe, and don't expect to; >> > > > but he's probably right, given the current code. I just dislike adding >> > > > unnecessary complexity, and siting it in the wrong place (mm/shmem.c). >> > > > >> > > > Yang, is it possible that 5.1 commit 8fd2e0b505d1 ("mm: swap: check if >> > > > swap backing device is congested or not") was actually developed and >> > > > measured on 4.1 or earlier, which still had blk_set_queue_congested()? >> > > >> > > I forgot the exact version, but definitely not 4.1 or earlier. Maybe >> > > 4.19 or earlier. I'm not familiar with how block layer detect >> > > congestion, if the logic was changed, hence the optimization doesn't >> > > stand anymore nowadays, I'm totally fine to remove it. >> > >> > You drove me back to look more closely. blk_set_queue_congested() >> > vanished from include/linux/blkdev.h in 4.2, but blk_set_congested() >> > appeared then in block/blk-core.c to replace it. blk_set_congested() >> > vanished (along with all references to "congested" in blk-core.c) in >> > 5.0, then your commit (most probably tested on 4.19) went into 5.1 - >> > just after it had become redundant! >> > >> > Thanks, yes, let's revert that and Miaohe's and Huang's, later on. >> >> It should be easier to revert Huang Ying's , then Miaohe's, then mine. > > Hi Ying, > > I just prepared the reverts since I need to revert yours and Miaohe's > in order to revert my problematic commit.
If your original commit will be reverted, then mine and Miaohe's can be reverted from the race condition point of view.
Although I still think it's better to call get/put_swap_device() in shmem_swapin_page(), that can be discussed with another patch.
Best Regards, Huang, Ying
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