On Mon, 20 Jan 2020, Chris Down wrote: > Hi Hugh, > > Sorry this response took so long, I had some non-work issues that took a lot > of time last week. No, clearly it's I who must apologize to you for very slow response. > > Hugh Dickins writes: > > > > 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? I was uncomfortable with tmpfs depleting get_next_ino()'s pool in some configurations, and wanted the (get_next_ino-like) per-cpu but per-sb batching for nr_inodes=0, to minimize its stat_lock contention. I did not have a patch to shmem_encode_fh(), had gone through thinking that 64-bit inos made an additional fix there necessary; but Amir then educated us that it is safe as is, though could be cleaned up later. nr_inodes can be 0 on non-internal mounts, for many years. > > For batching, I'm neutral. I'm happy to use the approach from your patch and > integrate it (and credit you, of course). Credit not important, but you may well want to blame me for that complication :) > > For shmem_encode_fh, I'm not totally sure I understand the concern, if that's > what you mean. My concern had been that shmem_encode_fh() builds up an fh from i_ino and more, looks well prepared for a 64-bit ino, but appeared to be announcing a 32-bit ino in its return value: Amir reassures us that that return value does not matter. > > 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. nr_inodes=0 is an intentional configuration (but 0 denoting infinity: not very clean, and I've sometimes regretted that choice). If there's any behavior change, that's a separate matter from these 64-bit ino patches; maybe I mentioned it in passing and confused us - that we seem to have recently allowed a remounting limited<->unlimited that was not permitted before, and might or might not need a fix patch. Sorry again for delaying you, Chris: not at all what I'd wanted to do. Hugh
