Messages in this thread | | | Date | Thu, 12 May 2022 20:27:12 +0800 | Subject | Re: [PATCHSETS] v14 fsdax-rmap + v11 fsdax-reflink | From | Shiyang Ruan <> |
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在 2022/5/11 23:46, Dan Williams 写道: > On Wed, May 11, 2022 at 8:21 AM Darrick J. Wong <djwong@kernel.org> wrote: >> >> Oan Tue, May 10, 2022 at 10:24:28PM -0700, Andrew Morton wrote: >>> On Tue, 10 May 2022 19:43:01 -0700 "Darrick J. Wong" <djwong@kernel.org> wrote: >>> >>>> On Tue, May 10, 2022 at 07:28:53PM -0700, Andrew Morton wrote: >>>>> On Tue, 10 May 2022 18:55:50 -0700 Dan Williams <dan.j.williams@intel.com> wrote: >>>>> >>>>>>> It'll need to be a stable branch somewhere, but I don't think it >>>>>>> really matters where al long as it's merged into the xfs for-next >>>>>>> tree so it gets filesystem test coverage... >>>>>> >>>>>> So how about let the notify_failure() bits go through -mm this cycle, >>>>>> if Andrew will have it, and then the reflnk work has a clean v5.19-rc1 >>>>>> baseline to build from? >>>>> >>>>> What are we referring to here? I think a minimal thing would be the >>>>> memremap.h and memory-failure.c changes from >>>>> https://lkml.kernel.org/r/20220508143620.1775214-4-ruansy.fnst@fujitsu.com ? >>>>> >>>>> Sure, I can scoot that into 5.19-rc1 if you think that's best. It >>>>> would probably be straining things to slip it into 5.19. >>>>> >>>>> The use of EOPNOTSUPP is a bit suspect, btw. It *sounds* like the >>>>> right thing, but it's a networking errno. I suppose livable with if it >>>>> never escapes the kernel, but if it can get back to userspace then a >>>>> user would be justified in wondering how the heck a filesystem >>>>> operation generated a networking errno? >>>> >>>> <shrug> most filesystems return EOPNOTSUPP rather enthusiastically when >>>> they don't know how to do something... >>> >>> Can it propagate back to userspace? >> >> AFAICT, the new code falls back to the current (mf_generic_kill_procs) >> failure code if the filesystem doesn't provide a ->memory_failure >> function or if it returns -EOPNOSUPP. mf_generic_kill_procs can also >> return -EOPNOTSUPP, but all the memory_failure() callers (madvise, etc.) >> convert that to 0 before returning it to userspace. >> >> I suppose the weirder question is going to be what happens when madvise >> starts returning filesystem errors like EIO or EFSCORRUPTED when pmem >> loses half its brains and even the fs can't deal with it. > > Even then that notification is not in a system call context so it > would still result in a SIGBUS notification not a EOPNOTSUPP return > code. The only potential gap I see are what are the possible error > codes that MADV_SOFT_OFFLINE might see? The man page is silent on soft > offline failure codes. Shiyang, that's something to check / update if > necessary.
According to the code around MADV_SOFT_OFFLINE, it will return -EIO when the backend is NVDIMM.
Here is the logic: madvise_inject_error() { ... if (MADV_SOFT_OFFLINE) { ret = soft_offline_page() { ... /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ page = pfn_to_online_page(pfn); if (!page) { put_ref_page(ref_page); return -EIO; } ... } } else { ret = memory_failure() } return ret }
-- Thanks, Ruan.
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