On Tue, 2021-09-28 at 11:36 +0530, Venky Shankar wrote: > v3: > - create mount syntax debugfs entries under /<>/ceph/meta/client_features directory > - mount syntax debugfs file names are v1, v2,... (were v1_mount_sytnax,... earlier) > > [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/meta > /sys/kernel/debug/ceph/meta/client_features > /sys/kernel/debug/ceph/meta/client_features/v2 > /sys/kernel/debug/ceph/meta/client_features/v1 > .... > .... > The patches look fine, technically, so I think we're down to the bikeshedding here. My minor gripe is that "v1" and "v2" are not really client features. Perhaps we should call these "mount_format_v1" or maybe "mount_syntax_v1" ? I could forsee is advertising other features in this dir in the future, and at that point "v1" and "v2" are somewhat ambiguous for names. Make sense? > 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 | 41 ++++++++++++++++++++++++++++++++++++ > fs/ceph/super.c | 3 +++ > fs/ceph/super.h | 2 ++ > include/linux/ceph/debugfs.h | 2 ++ > net/ceph/debugfs.c | 3 ++- > 5 files changed, 50 insertions(+), 1 deletion(-) > -- Jeff Layton <jlayton@xxxxxxxxxx>
