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NFSv4: Fix CLOSE races with OPEN

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If the reply to a successful CLOSE call races with an OPEN to the same
file, we can end up scribbling over the stateid that represents the
new open state.
The race looks like:

  Client				Server
  ======				======

  CLOSE stateid A on file "foo"
					CLOSE stateid A, return stateid C
  OPEN file "foo"
					OPEN "foo", return stateid B
  Receive reply to OPEN
  Reset open state for "foo"
  Associate stateid B to "foo"

  Receive CLOSE for A
  Reset open state for "foo"
  Replace stateid B with C

The fix is to examine the argument of the CLOSE, and check for a match
with the current stateid "other" field. If the two do not match, then
the above race occurred, and we should just ignore the CLOSE.

Reported-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Trond Myklebust 2016-11-14 11:19:55 -05:00 committed by Anna Schumaker
parent 23ea44c215
commit 3e7dfb1659
2 changed files with 13 additions and 6 deletions
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7
fs/nfs/nfs4_fs.h
View file

@ -542,6 +542,13 @@ static inline bool nfs4_valid_open_stateid(const struct nfs4_state *state)
return test_bit(NFS_STATE_RECOVERY_FAILED, &state->flags) == 0; return test_bit(NFS_STATE_RECOVERY_FAILED, &state->flags) == 0;
} }
static inline bool nfs4_state_match_open_stateid_other(const struct nfs4_state *state,
const nfs4_stateid *stateid)
{
return test_bit(NFS_OPEN_STATE, &state->flags) &&
nfs4_stateid_match_other(&state->open_stateid, stateid);
}
#else #else
#define nfs4_close_state(a, b) do { } while (0) #define nfs4_close_state(a, b) do { } while (0)

12
fs/nfs/nfs4proc.c
View file

@ -1451,7 +1451,6 @@ static void nfs_resync_open_stateid_locked(struct nfs4_state *state)
} }
static void nfs_clear_open_stateid_locked(struct nfs4_state *state, static void nfs_clear_open_stateid_locked(struct nfs4_state *state,
nfs4_stateid *arg_stateid,
nfs4_stateid *stateid, fmode_t fmode) nfs4_stateid *stateid, fmode_t fmode)
{ {
clear_bit(NFS_O_RDWR_STATE, &state->flags); clear_bit(NFS_O_RDWR_STATE, &state->flags);
@ -1469,10 +1468,9 @@ static void nfs_clear_open_stateid_locked(struct nfs4_state *state,
} }
if (stateid == NULL) if (stateid == NULL)
return; return;
/* Handle races with OPEN */ /* Handle OPEN+OPEN_DOWNGRADE races */
if (!nfs4_stateid_match_other(arg_stateid, &state->open_stateid) || if (nfs4_stateid_match_other(stateid, &state->open_stateid) &&
(nfs4_stateid_match_other(stateid, &state->open_stateid) && !nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
!nfs4_stateid_is_newer(stateid, &state->open_stateid))) {
nfs_resync_open_stateid_locked(state); nfs_resync_open_stateid_locked(state);
return; return;
} }
@ -1486,7 +1484,9 @@ static void nfs_clear_open_stateid(struct nfs4_state *state,
nfs4_stateid *stateid, fmode_t fmode) nfs4_stateid *stateid, fmode_t fmode)
{ {
write_seqlock(&state->seqlock); write_seqlock(&state->seqlock);
nfs_clear_open_stateid_locked(state, arg_stateid, stateid, fmode); /* Ignore, if the CLOSE argment doesn't match the current stateid */
if (nfs4_state_match_open_stateid_other(state, arg_stateid))
nfs_clear_open_stateid_locked(state, stateid, fmode);
write_sequnlock(&state->seqlock); write_sequnlock(&state->seqlock);
if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags))
nfs4_schedule_state_manager(state->owner->so_server->nfs_client); nfs4_schedule_state_manager(state->owner->so_server->nfs_client);