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authorTrond Myklebust <trond.myklebust@hammerspace.com>2018-06-20 17:53:34 -0400
committerTrond Myklebust <trond.myklebust@hammerspace.com>2019-02-21 13:22:43 -0500
commit3453d5708b33efe76f40eca1c0ed60923094b971 (patch)
tree54f690ed32d37f631561238542b211e955f1713d /fs/nfs/nfs4session.c
parent6f903b111e33c4f0c349402efbd5319f52362f8e (diff)
NFSv4.1: Avoid false retries when RPC calls are interrupted
A 'false retry' in NFSv4.1 occurs when the client attempts to transmit a new RPC call using a slot+sequence number combination that references an already cached one. Currently, the Linux NFS client will do this if a user process interrupts an RPC call that is in progress. The problem with doing so is that we defeat the main mechanism used by the server to differentiate between a new call and a replayed one. Even if the server is able to perfectly cache the arguments of the old call, it cannot know if the client intended to replay or send a new call. The obvious fix is to bump the sequence number pre-emptively if an RPC call is interrupted, but in order to deal with the corner cases where the interrupted call is not actually received and processed by the server, we need to interpret the error NFS4ERR_SEQ_MISORDERED as a sign that we need to either wait or locate a correct sequence number that lies between the value we sent, and the last value that was acked by a SEQUENCE call on that slot. Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> Tested-by: Jason Tibbitts <tibbs@math.uh.edu>
Diffstat (limited to 'fs/nfs/nfs4session.c')
-rw-r--r--fs/nfs/nfs4session.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index 25c5255a395c..bcb532def9e2 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -110,6 +110,8 @@ static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table *tbl,
slot->table = tbl;
slot->slot_nr = slotid;
slot->seq_nr = seq_init;
+ slot->seq_nr_highest_sent = seq_init;
+ slot->seq_nr_last_acked = seq_init - 1;
}
return slot;
}
@@ -276,7 +278,8 @@ static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
p = &tbl->slots;
while (*p) {
(*p)->seq_nr = ivalue;
- (*p)->interrupted = 0;
+ (*p)->seq_nr_highest_sent = ivalue;
+ (*p)->seq_nr_last_acked = ivalue - 1;
p = &(*p)->next;
}
tbl->highest_used_slotid = NFS4_NO_SLOT;