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  1. 02 Oct, 2020 2 commits
    • Benjamin Coddington's avatar
      NFSv4: Wait for stateid updates after CLOSE/OPEN_DOWNGRADE · b4868b44
      Benjamin Coddington authored 
      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: default avatarBenjamin Coddington <bcodding@redhat.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
      b4868b44
    • Nick Desaulniers's avatar
      nfs: remove incorrect fallthrough label · fb08334b
      Nick Desaulniers authored 
      There is no case after the default from which to fallthrough to. Clang
will error in this case (unhelpfully without context, see link below)
and GCC will with -Wswitch-unreachable.

The previous commit should have just replaced the comment with a break
statement.

If we consider implicit fallthrough to be a design mistake of C, then
all case statements should be terminated with one of the following
statements:
* break
* continue
* return
* fallthrough
* goto
* (call of function with __attribute__(__noreturn__))

Fixes: 2a1390c95a69 ("nfs: Convert to use the preferred fallthrough macro")
Link: https://bugs.llvm.org/show_bug.cgi?id=47539Acked-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarNathan Chancellor <natechancellor@gmail.com>
Suggested-by: default avatarJoe Perches <joe@perches.com>
Signed-off-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
      fb08334b
  3. 24 Sep, 2020 2 commits
  5. 21 Sep, 2020 33 commits
  7. 20 Sep, 2020 3 commits
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