.On Sat, May 18, 2019 at 6:21 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > On Sat, May 18, 2019 at 05:00:39PM +0200, Dmitry Vyukov wrote: > > On Fri, May 17, 2019 at 4:08 PM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > > > > > On Fri, May 17, 2019 at 3:48 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Fri, May 17, 2019 at 03:17:02AM -0700, syzbot wrote: > > > > > This bug is marked as fixed by commit: > > > > > vfs: namespace: error pointer dereference in do_remount() > > > > > But I can't find it in any tested tree for more than 90 days. > > > > > Is it a correct commit? Please update it by replying: > > > > > #syz fix: exact-commit-title > > > > > Until then the bug is still considered open and > > > > > new crashes with the same signature are ignored. > > > > > > > > Could somebody explain how the following situation is supposed to > > > > be handled: > > > > > > > > 1) branch B1 with commits C1, C2, C3, C4 is pushed out > > > > 2) C2 turns out to have a bug, which gets caught and fixed > > > > 3) fix is folded in and branch B2 with C1, C2', C3', C4' is > > > > pushed out. The bug is not in it anymore. > > > > 4) B1 is left mouldering (or is entirely removed); B2 is > > > > eventually merged into other trees. > > > > > > > > This is normal and it appears to be problematic for syzbot. > > > > How to deal with that? One thing I will *NOT* do in such > > > > situations is giving up on folding the fixes in. Bisection > > > > hazards alone make that a bad idea. > > > > > > linux-next creates a bit of a havoc. > > > > > > The ideal way of handling this is including Tested-by: tag into C2'. > > > Reported-by: would work too, but people suggested that Reported-by: is > > > confusing in this situation because it suggests that the commit fixes > > > a bug in some previous commit. Technically, syzbot now accepts any > > > tag, so With-inputs-from: > > > syzbot+73c7fe4f77776505299b@xxxxxxxxxxxxxxxxxxxxxxxxx would work too. > > > > > > At this point we obvious can't fix up C2'. For such cases syzbot > > > accepts #syz fix command to associate bugs with fixes. So replying > > > with "#syz fix: C2'-commit-title" should do. > > > > What is that C2'? > > In this case? Take a look at > > commit fd0002870b453c58d0d8c195954f5049bc6675fb > Author: David Howells <dhowells@xxxxxxxxxx> > Date: Tue Aug 28 14:45:06 2018 +0100 > > vfs: Implement a filesystem superblock creation/configuration context > > and compare with > > commit f18edd10d3c7d6127b1fa97c8f3299629cf58ed5 > Author: David Howells <dhowells@xxxxxxxxxx> > Date: Thu Nov 1 23:07:25 2018 +0000 > > vfs: Implement a filesystem superblock creation/configuration context > > There might have been intermediate forms, but that should illustrate what > happened. Diff of those two contains (among other things) this: > @@ -985,6 +989,9 @@ > + fc = vfs_new_fs_context(path->dentry->d_sb->s_type, > + path->dentry, sb_flags, MS_RMT_MASK, > + FS_CONTEXT_FOR_RECONFIGURE); > ++ err = PTR_ERR(fc); > ++ if (IS_ERR(fc)) > ++ goto err; > + > + err = parse_monolithic_mount_data(fc, data, data_size); > + if (err < 0) > > IOW, Dan's fix folded into the offending commit. And that kind of > pattern is not rare; I would argue that appending Dan's patch at > the end of queue and leaving the crap in between would be a fucking > bad idea - it would've left a massive bisection hazard *and* made > life much more unpleasant when the things got to merging into the > mainline (or reviewing, for that matter). > > What would you prefer to happen in such situations? Commit summaries > modified enough to confuse CI tools into *NOT* noticing that those > are versions of the same patch? Some kind of metadata telling the > same tools that such-and-such commits got folded in (and they might > have been split in process, with parts folded into different spots > in the series, at that)? > > Because "never fold in, never reorder, just accumulate patches in > the end of the series" is not going to fly. For a lot of reasons. I don't advocate for stopping folding/amending/rebasing patches in any way. I understand this is required to get sane commits. But what I said in the previous email still applies: - either include the tag into the first commit version that fixes the reported bug - or link report and the fixing commit manually using the final commit title As far as I understand in this case it would be adding Tested-by (or some other tag) to f18edd10d3c7d6127b1fa97c8f3299629cf58ed5. We can't do this now, so this should work: #syz fix: vfs: Implement a filesystem superblock creation/configuration context
