On Mon, Jun 11, 2019 at 04:41:54PM -0400, Theodore Ts'o wrote: > On Mon, Jun 10, 2019 at 09:09:34AM -0700, Darrick J. Wong wrote: > > > I was planning on only taking 8/8 through the ext4 tree. I also added > > > a patch which filtered writes, truncates, and page_mkwrites (but not > > > mmap) for immutable files at the ext4 level. > > > > *Oh*. I saw your reply attached to the 1/8 patch and thought that was > > the one you were taking. I was sort of surprised, tbh. :) > > Sorry, my bad. I mis-replied to the wrong e-mail message :-) > > > > I *could* take this patch through the mm/fs tree, but I wasn't sure > > > what your plans were for the rest of the patch series, and it seemed > > > like it hadn't gotten much review/attention from other fs or mm folks > > > (well, I guess Brian Foster weighed in). > > > > > What do you think? > > > > Not sure. The comments attached to the LWN story were sort of nasty, > > and now that a couple of people said "Oh, well, Debian documented the > > inconsistent behavior so just let it be" I haven't felt like > > resurrecting the series for 5.3. > > Ah, I had missed the LWN article. <Looks> > > Yeah, it's the same set of issues that we had discussed when this > first came up. We can go round and round on this one; It's true that > root can now cause random programs which have a file mmap'ed for > writing to seg fault, but root has a million ways of killing and > otherwise harming running application programs, and it's unlikely > files get marked for immutable all that often. We just have to pick > one way of doing things, and let it be same across all the file > systems. > > My understanding was that XFS had chosen to make the inode immutable > as soon as the flag is set (as opposed to forbidding new fd's to be > opened which were writeable), and I was OK moving ext4 to that common > interpretation of the immmutable bit, even though it would be a change > to ext4. <nod> It started as "just do this to xfs" and has now become a vfs level change... > And then when I saw that Amir had included a patch that would cause > test failures unless that patch series was applied, it seemed that we > had all thought that the change was a done deal. Perhaps we should > have had a more explicit discussion when the test was sent for review, > but I had assumed it was exclusively a copy_file_range set of tests, > so I didn't realize it was going to cause ext4 failures. And here we see the inconsistent behavior causing developer confusion. :) I think Amir's c_f_r tests just check the existing behavior (of just c_f_r) that you can't (most of the time) copy into a file that you opened for write but that the administrator has since marked immutable. /That/ behavior in turn came from the original implementation that would try reflink which would fail on the immutable destination check and then fail the whole call ... I think? --D > - Ted
