Messages in this thread | | | Date | Thu, 20 Aug 2020 04:15:09 +0800 | From | Gao Xiang <> | Subject | Re: [PATCH] mm, THP, swap: fix allocating cluster for swapfile by mistake |
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Hi Andrew,
On Wed, Aug 19, 2020 at 01:05:06PM -0700, Andrew Morton wrote: > On Thu, 20 Aug 2020 03:56:13 +0800 Gao Xiang <hsiangkao@redhat.com> wrote: > > > SWP_FS doesn't mean the device is file-backed swap device, > > which just means each writeback request should go through fs > > by DIO. Or it'll just use extents added by .swap_activate(), > > but it also works as file-backed swap device. > > This is very hard to understand :(
Thanks for your reply...
The related logic is in __swap_writepage() and setup_swap_extents(), and also see e.g generic_swapfile_activate() or iomap_swapfile_activate()...
I will also talk with "Huang, Ying" in person if no response here.
> > > So in order to achieve the goal of the original patch, > > SWP_BLKDEV should be used instead. > > > > FS corruption can be observed with SSD device + XFS + > > fragmented swapfile due to CONFIG_THP_SWAP=y. > > > > Fixes: f0eea189e8e9 ("mm, THP, swap: Don't allocate huge cluster for file backed swap device") > > Fixes: 38d8b4e6bdc8 ("mm, THP, swap: delay splitting THP during swap out") > > Why do you think it has taken three years to discover this?
I'm not sure if the Redhat BZ is available for public, it can be reproduced since rhel 8 https://bugzilla.redhat.com/show_bug.cgi?id=1855474
It seems hard to believe, but I think just because rare user uses the SSD device + THP + file-backed swap device combination... maybe I'm wrong here, but my test shows as it is.
Thanks, Gao Xiang
> > >
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