Cleanup: Make memory barrier definitions consistent across kernels

We inherited membar_consumer() and membar_producer() from OpenSolaris,
but we had replaced membar_consumer() with Linux's smp_rmb() in
zfs_ioctl.c. The FreeBSD SPL consequently implemented a shim for the
Linux-only smp_rmb().

We reinstate membar_consumer() in platform independent code and fix the
FreeBSD SPL to implement membar_consumer() in a way analogous to Linux.

Reviewed-by: Konstantin Belousov <kib@FreeBSD.org>
Reviewed-by: Mateusz Guzik <mjguzik@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Neal Gompa <ngompa@datto.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13843

diff --git a/include/os/freebsd/linux/compiler.h b/include/os/freebsd/linux/compiler.h
index 3a66da195891eee54120c13631689270db84cb81..b408b77c746d2c1f06b615cfce7cf673eba5a88e 100644 (file)
--- a/include/os/freebsd/linux/compiler.h
+++ b/include/os/freebsd/linux/compiler.h
@@ -83,7 +83,6 @@
 #define        __printf(a, b)                  __printflike(a, b)
 
 #define        barrier()                       __asm__ __volatile__("": : :"memory")
-#define        smp_rmb()               rmb()
 #define        ___PASTE(a, b) a##b
 #define        __PASTE(a, b) ___PASTE(a, b)
 

diff --git a/include/os/freebsd/spl/sys/atomic.h b/include/os/freebsd/spl/sys/atomic.h
index 1a68bfc4de23cffa0492b2717c52ac38ff76076d..01b13fc9afd7f6698f6ae1db1f63e0582d1e8595 100644 (file)
--- a/include/os/freebsd/spl/sys/atomic.h
+++ b/include/os/freebsd/spl/sys/atomic.h
@@ -57,7 +57,8 @@ extern uint64_t atomic_cas_64(volatile uint64_t *target, uint64_t cmp,
     uint64_t newval);
 #endif
 
-#define        membar_producer atomic_thread_fence_rel
+#define        membar_consumer()               atomic_thread_fence_acq()
+#define        membar_producer()               atomic_thread_fence_rel()
 
 static __inline uint32_t
 atomic_add_32_nv(volatile uint32_t *target, int32_t delta)

diff --git a/include/os/linux/spl/sys/vmsystm.h b/include/os/linux/spl/sys/vmsystm.h
index b3f121ecf0ca55ce78a89daf0e34288eec5e75ad..fcd61e818fa3138cf74021cc61bcdb56ba29535e 100644 (file)
--- a/include/os/linux/spl/sys/vmsystm.h
+++ b/include/os/linux/spl/sys/vmsystm.h
@@ -44,7 +44,9 @@
 #define        zfs_totalhigh_pages     totalhigh_pages
 #endif
 
+#define        membar_consumer()               smp_rmb()
 #define        membar_producer()               smp_wmb()
+
 #define        physmem                         zfs_totalram_pages
 
 #define        xcopyin(from, to, size)         copy_from_user(to, from, size)

diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 382975208b9747f077e4d78e91e6e3b21883e211..6b9b43271ba999d154123c2a0f371fb5c8cbc811 100644 (file)
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -7482,7 +7482,7 @@ zfsdev_get_state(minor_t minor, enum zfsdev_state_type which)
 
        for (zs = zfsdev_state_list; zs != NULL; zs = zs->zs_next) {
                if (zs->zs_minor == minor) {
-                       smp_rmb();
+                       membar_consumer();
                        switch (which) {
                        case ZST_ONEXIT:
                                return (zs->zs_onexit);