> > >> There is also another bug: > > >> > > >> https://bugs.linaro.org/show_bug.cgi?id=3303. > > >> > > >> Fanotify faces a srcu dead-lock when userland stops responding to > > >> events for this other case. Fix for that bug is a 35 patches patchset > > >> (including the fix, commit 9dd813c15b2c101, for the particular > > >> issue). > > >> > > >> Question is, should I document things of this nature on this list also > > >> ? Even if it is likely a no-go for the backports ? Just as information > > >> ? Should I just bring the attention to the backport need (all patches) > > >> and you decide ? > > > > > > Same as above, if you test them and they work, and they resolve a > > > reported and testable bug, why wouldn't we apply them? > > > > > > > So this is the story with overlayfs - besides NFS export in v4.16, > > I don't think overlayfs got any new "features". Since the day it was > > merged upstream (v3.18) it was all about fixing bugs and > > "non-standard-behaviors": > > https://github.com/amir73il/overlayfs/wiki/Overlayfs-non-standard-behavior > > > > Are those non-standard behaviors reported and testable bugs? yes > > but they have been around for so long that applications may have > > become dependent on the non-standard-behavior, so the "bug fixes" > > are often introduced as "features" that are off by default and need to > > be explicitly enabled by config/module/mount option (e.g. redirect_dir > > added in v4.10). > > > > Now if you want to apply all the fixes to non-standard-behavior, > > I am maintaining a 4.9.y backport branch with *everything*: > > https://github.com/amir73il/linux/commits/overlayfs-4.9.y > > > > So this branch also includes the NFS export feature, but I suspect > > it going to be hairy to apply $SUBJECT fix in question without applying > > the NFS export patches. > > > > What does the new benevolent Greg have to say about this? > > Would you consider taking all non-standard-behavior fixes to stable? > > If you do, I can help with maintaining the stable overlayfs branches. > > I'd prefer to stick with as close-to-possible as what Linus's tree has. > But for stuff like this, maybe it just makes sense to leave it all alone > and if people want the newer "features" they need to move to a newer > kernel, like they should be doing anyway. > > So for now, let's just leave it as-is, if anyone complains we can > revisit and look at the patches that are needed for backporting. > > sound reasonable? > Greg, As spoke in this thread last week, I have prepared a patchset for v4.9 tree for one of the bugs I mentioned (https://bugs.linaro.org/show_bug.cgi?id=3303). This bug is related to a dead-lock in kernel waiting for userland events (fanotify). Short Summary of BUG: https://bugs.linaro.org/show_bug.cgi?id=3303#c16 Full conclusion after kdump analysis: https://bugs.linaro.org/show_bug.cgi?id=3303#c14 The patch list for resolution is: ** [35/35] 054c636e5c80 fsnotify: Move ->free_mark callback to fsnotify_ops ok [34/35] 7b1293234084 fsnotify: Add group pointer in fsnotify_init_mark() ok [33/35] ebb3b47e37a4 fsnotify: Drop inode_mark.c ok [32/35] b1362edfe15b fsnotify: Remove fsnotify_find_{inode|vfsmount}_mark() ok [31/35] 2e37c6ca8d76 fsnotify: Remove fsnotify_detach_group_marks() ok [30/35] 18f2e0d3a436 fsnotify: Rename fsnotify_clear_marks_by_group_flags() ok [29/35] 416bcdbcbbb4 fsnotify: Inline fsnotify_clear_{inode|vfsmount}_mark_group() ok [28/35] 8920d2734d9a fsnotify: Remove fsnotify_recalc_{inode|vfsmount}_mask() ok [27/35] 66d2b81bcb92 fsnotify: Remove fsnotify_set_mark_{,ignored_}mask_locked() ok [26/35] 05f0e38724e8 fanotify: Release SRCU lock when waiting for userspace response ok [25/35] 9385a84d7e1f fsnotify: Pass fsnotify_iter_info into handle_event handler ** [NEED ] 3cd5eca8d7a2 fsnotify: constify 'data' passed to ->handle_event() ok [24/35] abc77577a669 fsnotify: Provide framework for dropping SRCU lock in ->handle_event ok [23/35] f09b04a03e02 fsnotify: Remove special handling of mark destruction on group shutdown ok [22/35] 6b3f05d24d35 fsnotify: Detach mark from object list when last reference is dropped ok [21/35] 11375145a70d fsnotify: Move queueing of mark for destruction into fsnotify_put_mark() ok [20/35] e7253760587e inotify: Do not drop mark reference under idr_lock ok [19/35] 08991e83b728 fsnotify: Free fsnotify_mark_connector when there is no mark attached ok [18/35] 04662cab59fc fsnotify: Lock object list with connector lock ok [17/35] 2629718dd26f fsnotify: Remove useless list deletion and comment ok [16/35] 73cd3c33ab79 fsnotify: Avoid double locking in fsnotify_detach_from_object() ok [15/35] 8212a6097a72 fsnotify: Remove indirection from fsnotify_detach_mark() ok [14/35] a03e2e4f0783 fsnotify: Determine lock in fsnotify_destroy_marks() ok [13/35] f06fd9875945 fsnotify: Move locking into fsnotify_find_mark() ok [12/35] a242677bb1e6 fsnotify: Move locking into fsnotify_recalc_mask() ok [11/35] 0810b4f9f207 fsnotify: Move fsnotify_destroy_marks() ok [10/35] 755b5bc681eb fsnotify: Remove indirection from mark list addition ok [09/35] e911d8af87db fsnotify: Make fsnotify_mark_connector hold inode reference ok [08/35] 86ffe245c430 fsnotify: Move object pointer to fsnotify_mark_connector ok [NEED ] be29d20f3f5d audit: Fix sleep in atomic ok [NEED ] e3ba730702af fsnotify: Remove fsnotify_duplicate_mark() ** [07/35] 9dd813c15b2c fsnotify: Move mark list head from object into dedicated structure -> THIS ONE ok [06/35] c1f33073ac1b fsnotify: Update comments ok [05/35] 43471d15df0e audit_tree: Use mark flags to check whether mark is alive ok [04/35] f410ff65548c audit: Abstract hash key handling ok [03/35] c97476400d3b fanotify: Move recalculation of inode / vfsmount mask under mark_mutex ok [02/35] 25c829afbd74 inotify: Remove inode pointers from debug messages ok [01/35] 5198adf649a0 fsnotify: Remove unnecessary tests when showing fdinfo ok = cherry-pick (no changes needed) ** = backport [NEED] = needed for original patchset to be cherry-picked (Original patchset came from https://www.spinics.net/lists/linux-fsdevel/msg109131.html and there was 3 backports for positional changes and 3 patches to satisfy the cherry-picks). And it merges with no issues in stable v4.9 tree (as you can see in https://bugs.linaro.org/show_bug.cgi?id=3303#c21). I can submit in a thread in stable list if you are willing to move further. As you can see, this patchset solves the issue: BUG [unpatched] https://bugs.linaro.org/show_bug.cgi?id=3303#c18 SOLVED [patched] https://bugs.linaro.org/show_bug.cgi?id=3303#c19 And introduces NO regressions in LTP or KSELFTEST: KSELFTEST: https://bugs.linaro.org/show_bug.cgi?id=3303#c23 LTP: https://bugs.linaro.org/show_bug.cgi?id=3303#c27 I think now we've reached the "It depends" phase =). Let me know if you think this is good to be acceptable for v4.9. We can run full round of tests (on all boards and x86/amd64) if you choose to pull this, during stable review. I can try same thing for v4.4 if it is worth. Cheers o/ -Rafael
