On Fri, 2021-10-01 at 10:30 +0530, Venky Shankar wrote:
> v4:
> - use mount_syntax_v1,.. as file names
>
> [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/mount_syntax_v2
> /sys/kernel/debug/ceph/meta/client_features/mount_syntax_v1
> ....
> ....
>
> 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(-)
>
This looks good to me. Merged into testing branch.
Note that there is a non-zero chance that this will break teuthology in
some wa. In particular, looking at qa/tasks/cephfs/kernel_mount.py, it
does this in _get_global_id:
pyscript = dedent("""
import glob
import os
import json
def get_id_to_dir():
result = {}
for dir in glob.glob("/sys/kernel/debug/ceph/*"):
mds_sessions_lines = open(os.path.join(dir, "mds_sessions")).readlines()
global_id = mds_sessions_lines[0].split()[1].strip('"')
client_id = mds_sessions_lines[1].split()[1].strip('"')
result[client_id] = global_id
return result
print(json.dumps(get_id_to_dir()))
""")
What happens when this hits the "meta" directory? Is that a problem?
We may need to fix up some places like this. Maybe the open there needs
some error handling? Or we could just skip directories called "meta".
--
Jeff Layton <jlayton@xxxxxxxxxx>
