On Wed, Aug 25, 2021 at 10:57 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > On Wed, 2021-08-25 at 11:20 +0530, Venky Shankar wrote: > > v2: > > - export ceph_debugfs_dir > > - include v1 mount support debugfs entry > > - create debugfs entries under /<>/ceph/client_features dir > > > > [This is based on top of new mount syntax series] > > > > Patrick proposed the idea of having debugfs entries to signify if > > kernel supports the new (v2) mount syntax. The primary use of this > > information is to catch any bugs in the new syntax implementation. > > > > This would be done as follows:: > > > > The userspace mount helper tries to mount using the new mount syntax > > and fallsback to using old syntax if the mount using new syntax fails. > > However, a bug in the new mount syntax implementation can silently > > result in the mount helper switching to old syntax. > > > > So, the debugfs entries can be relied upon by the mount helper to > > check if the kernel supports the new mount syntax. Cases when the > > mount using the new syntax fails, but the kernel does support the > > new mount syntax, the mount helper could probably log before switching > > to the old syntax (or fail the mount altogether when run in test mode). > > > > Debugfs entries are as follows:: > > > > /sys/kernel/debug/ceph/ > > .... > > .... > > /sys/kernel/debug/ceph/client_features > > /sys/kernel/debug/ceph/client_features/v2_mount_syntax > > /sys/kernel/debug/ceph/client_features/v1_mount_syntax > > .... > > .... > > > > There are at least some scripts in teuthology that iterate over all of > the directories under /sys/kernel/debug/ceph/. Once you add this, some > of them may become confused. > > I think we might want a more generic top-level directory for this sort > of thing, so that we only need to deal with the fallout once if we want > to put other generic info in there. Hmm, makes sense. > > Maybe something like this? > > /sys/kernel/debug/ceph/meta/ > /sys/kernel/debug/ceph/meta/client_features > > I'd be open to different names for "meta" too. meta, misc, info, ... I do not have a strong opinion on the naming. > > Also, do we really want to present this info via directories? I would > have thought something more like a "meta/mount_syntax" file there that > just prints "v1 v2" when read. > > What's easier for scripting? One reason I kept these as files was to not do parsing stuff and just rely on stat(). > > > Venky Shankar (2): > > libceph: export ceph_debugfs_dir for use in ceph.ko > > ceph: add debugfs entries for mount syntax support > > > > fs/ceph/debugfs.c | 36 ++++++++++++++++++++++++++++++++++++ > > fs/ceph/super.c | 3 +++ > > fs/ceph/super.h | 2 ++ > > include/linux/ceph/debugfs.h | 2 ++ > > net/ceph/debugfs.c | 3 ++- > > 5 files changed, 45 insertions(+), 1 deletion(-) > > > > -- > Jeff Layton <jlayton@xxxxxxxxxx> > -- Cheers, Venky
