NFSv4: Wait for stateid updates after CLOSE/OPEN_DOWNGRADE
Since commit 0e0cb35b ("NFSv4: Handle NFS4ERR_OLD_STATEID in CLOSE/OPEN_DOWNGRADE") the following livelock may occur if a CLOSE races with the update of the nfs_state: Process 1 Process 2 Server ========= ========= ======== OPEN file OPEN file Reply OPEN (1) Reply OPEN (2) Update state (1) CLOSE file (1) Reply OLD_STATEID (1) CLOSE file (2) Reply CLOSE (-1) Update state (2) wait for state change OPEN file wake CLOSE file OPEN file wake CLOSE file ... ... We can avoid this situation by not issuing an immediate retry with a bumped seqid when CLOSE/OPEN_DOWNGRADE receives NFS4ERR_OLD_STATEID. Instead, take the same approach used by OPEN and wait at least 5 seconds for outstanding stateid updates to complete if we can detect that we're out of sequence. Note that after this change it is still possible (though unlikely) that CLOSE waits a full 5 seconds, bumps the seqid, and retries -- and that attempt races with another OPEN at the same time. In order to avoid this race (which would result in the livelock), update nfs_need_update_open_stateid() to handle the case where: - the state is NFS_OPEN_STATE, and - the stateid doesn't match the current open stateid Finally, nfs_need_update_open_stateid() is modified to be idempotent and renamed to better suit the purpose of signaling that the stateid passed is the next stateid in sequence. Fixes: 0e0cb35b ("NFSv4: Handle NFS4ERR_OLD_STATEID in CLOSE/OPEN_DOWNGRADE") Cc: stable@vger.kernel.org # v5.4+ Signed-off-by:Benjamin Coddington <bcodding@redhat.com> Signed-off-by:
Anna Schumaker <Anna.Schumaker@Netapp.com>
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fb08334b
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