pNFS: Tighten up locking around DS commit buckets

pNFS: Tighten up locking around DS commit buckets

Orabug: 25308025

[ Upstream commit 27571297a7e9a2a845c232813a7ba7e1227f5ec6 ]

I'm not aware of any bugreports around this issue, but the locking
around the pnfs_commit_bucket is inconsistent at best. This patch
tightens it up by ensuring that the 'bucket->committing' list is always
changed atomically w.r.t. the 'bucket->clseg' layout segment tracking.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 94d06a437eb0ad1a492ed75f929d82715b6c05f8)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>