diff options
| author | Paul Burton <paul.burton@mips.com> | 2018-11-01 17:51:34 +0000 |
|---|---|---|
| committer | Trond Myklebust <trond.myklebust@hammerspace.com> | 2018-11-01 13:55:24 -0400 |
| commit | c3be6577d82a9f0163eb1e2c37a477414d12a209 (patch) | |
| tree | d6cee7e555354f3f81f10b35b284b93fecc68ade /include | |
| parent | 86bbd7422ae6a33735df6846fd685e46686da714 (diff) | |
SUNRPC: Use atomic(64)_t for seq_send(64)
The seq_send & seq_send64 fields in struct krb5_ctx are used as
atomically incrementing counters. This is implemented using cmpxchg() &
cmpxchg64() to implement what amount to custom versions of
atomic_fetch_inc() & atomic64_fetch_inc().
Besides the duplication, using cmpxchg64() has another major drawback in
that some 32 bit architectures don't provide it. As such commit
571ed1fd2390 ("SUNRPC: Replace krb5_seq_lock with a lockless scheme")
resulted in build failures for some architectures.
Change seq_send to be an atomic_t and seq_send64 to be an atomic64_t,
then use atomic(64)_* functions to manipulate the values. The atomic64_t
type & associated functions are provided even on architectures which
lack real 64 bit atomic memory access via CONFIG_GENERIC_ATOMIC64 which
uses spinlocks to serialize access. This fixes the build failures for
architectures lacking cmpxchg64().
A potential alternative that was raised would be to provide cmpxchg64()
on the 32 bit architectures that currently lack it, using spinlocks.
However this would provide a version of cmpxchg64() with semantics a
little different to the implementations on architectures with real 64
bit atomics - the spinlock-based implementation would only work if all
access to the memory used with cmpxchg64() is *always* performed using
cmpxchg64(). That is not currently a requirement for users of
cmpxchg64(), and making it one seems questionable. As such avoiding
cmpxchg64() outside of architecture-specific code seems best,
particularly in cases where atomic64_t seems like a better fit anyway.
The CONFIG_GENERIC_ATOMIC64 implementation of atomic64_* functions will
use spinlocks & so faces the same issue, but with the key difference
that the memory backing an atomic64_t ought to always be accessed via
the atomic64_* functions anyway making the issue moot.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 571ed1fd2390 ("SUNRPC: Replace krb5_seq_lock with a lockless scheme")
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-nfs@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/sunrpc/gss_krb5.h | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/include/linux/sunrpc/gss_krb5.h b/include/linux/sunrpc/gss_krb5.h index 69f749afa617..4162de72e95c 100644 --- a/include/linux/sunrpc/gss_krb5.h +++ b/include/linux/sunrpc/gss_krb5.h @@ -107,8 +107,8 @@ struct krb5_ctx { u8 Ksess[GSS_KRB5_MAX_KEYLEN]; /* session key */ u8 cksum[GSS_KRB5_MAX_KEYLEN]; s32 endtime; - u32 seq_send; - u64 seq_send64; + atomic_t seq_send; + atomic64_t seq_send64; struct xdr_netobj mech_used; u8 initiator_sign[GSS_KRB5_MAX_KEYLEN]; u8 acceptor_sign[GSS_KRB5_MAX_KEYLEN]; @@ -118,9 +118,6 @@ struct krb5_ctx { u8 acceptor_integ[GSS_KRB5_MAX_KEYLEN]; }; -extern u32 gss_seq_send_fetch_and_inc(struct krb5_ctx *ctx); -extern u64 gss_seq_send64_fetch_and_inc(struct krb5_ctx *ctx); - /* The length of the Kerberos GSS token header */ #define GSS_KRB5_TOK_HDR_LEN (16) |