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authorPaul Burton <paul.burton@mips.com>2018-11-01 20:51:34 +0300
committerTrond Myklebust <trond.myklebust@hammerspace.com>2018-11-01 20:55:24 +0300
commitc3be6577d82a9f0163eb1e2c37a477414d12a209 (patch)
treed6cee7e555354f3f81f10b35b284b93fecc68ade /include/linux
parent86bbd7422ae6a33735df6846fd685e46686da714 (diff)
downloadlinux-c3be6577d82a9f0163eb1e2c37a477414d12a209.tar.xz
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/linux')
-rw-r--r--include/linux/sunrpc/gss_krb5.h7
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)