Messages in this thread |  | | Date | Mon, 20 Jan 2020 15:11:17 +0000 | From | Chris Down <> | Subject | Re: [PATCH v5 2/2] tmpfs: Support 64-bit inums per-sb |
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Hi Hugh,
Sorry this response took so long, I had some non-work issues that took a lot of time last week.
Hugh Dickins writes: >On Fri, 10 Jan 2020, Chris Down wrote: >> Hugh Dickins writes: >> > Dave, Amir, Chris, many thanks for the info you've filled in - >> > and absolutely no need to run any scan on your fleet for this, >> > I think we can be confident that even if fb had some 15-year-old tool >> > in use on its fleet of 2GB-file filesystems, it would not be the one >> > to insist on a kernel revert of 64-bit tmpfs inos. >> > >> > The picture looks clear now: while ChrisD does need to hold on to his >> > config option and inode32/inode64 mount option patch, it is much better >> > left out of the kernel until (very unlikely) proved necessary. >> >> Based on Mikael's comment above about Steam binaries, and the lack of >> likelihood that they can be rebuilt, I'm inclined to still keep inode{64,32}, >> but make legacy behaviour require explicit opt-in. That is: >> >> - Default it to inode64 >> - Remove the Kconfig option >> - Only print it as an option if tmpfs was explicitly mounted with inode32 >> >> The reason I suggest keeping this is that I'm mildly concerned that the kind >> of users who might be impacted by this change due to 32-bit _FILE_OFFSET_BITS >> -- like the not-too-uncommon case that Mikael brings up -- seem unlikely to >> be the kind of people that would find it in an rc. > >Okay. None of us are thrilled with it, but I agree that >Mikael's observation should override our developer's preference. > >So the "inode64" option will be accepted but redundant on mounting, >but exists for use as a remount option after mounting or remounting >with "inode32": allowing the admin to switch temporarily to mask off >the high ino bits with "inode32" when needing to run a limited binary. > >Documentation and commit message to alert Andrew and Linus and distros >that we are risking some breakage with this, but supplying the antidote >(not breakage of any distros themselves, no doubt they're all good; >but breakage of what some users might run on them).
Sounds good.
>> >> Other than that, the first patch could be similar to how it is now, >> incorporating Hugh's improvements to the first patch to put everything under >> the same stat_lock in shmem_reserve_inode. > >So, I persuaded Amir to the other aspects my version, but did not >persuade you? Well, I can live with that (or if not, can send mods >on top of yours): but please read again why I was uncomfortable with >yours, to check that you still prefer it (I agree that your patch is >simpler, and none of my discomfort decisive).
Hmm, which bit were you thinking of? The lack of batching, shmem_encode_fh(), or the fact that nr_inodes can now be 0 on non-internal mounts?
For batching, I'm neutral. I'm happy to use the approach from your patch and integrate it (and credit you, of course).
For shmem_encode_fh, I'm not totally sure I understand the concern, if that's what you mean.
For nr_inodes, I agree that intentional or unintentional, we should at least handle this case for now and can adjust later if the behaviour changes.
Thanks again,
Chris
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