On Wed, May 11, 2022 at 8:21 AM Darrick J. Wong <djwong@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxx> 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@xxxxxxxxxxx ? > > > > > > > > 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.
