Re: [RFC v2 PATCH 1/4] ceph: add seqlock for snaprealm hierarchy change detection

[Luis Henriques <lhenriques@suse.com>]

"Yan, Zheng" <ukernel@gmail.com> writes:

> On Mon, Dec 18, 2017 at 11:38 PM, Luis Henriques <lhenriques@suse.com> wrote:
<snip>
>>  /* snap.c */
>> +extern seqlock_t snaprealm_lock;
>> +
>>  struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
>>                                                u64 ino);
>>  extern void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
>> --
>
> For the above reason, I think we'd better not to introduce the new seq
> lock. Just read lock mdsc->snap_rwsem when walking the snaprealm
> hierarchy.

Thank you for the detailed review of this patch.  I guess my
understanding of the snaprealms handling wasn't quite correct.  Using
the snap_rwsem seems to make sense now after reading your comments and
re-reading the code.

I'll look at the code a bit more and eventually rework this patchset.
Dropping this patch will also allow simplifying patches 3 and 4.

Cheers,
-- 
Luis