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Replace hand-made exclusive lock, protecting against parallel

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swapon/swapoff invocations, with sx.

Reviewed by:	alc (as part of larger patch)
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2016-05-22 23:25:01 +00:00
parent aa1434ec54
commit 04533e1ef7
1 changed files with 10 additions and 24 deletions
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34
sys/vm/swap_pager.c
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@ -152,7 +152,7 @@ static TAILQ_HEAD(, swdevt) swtailq = TAILQ_HEAD_INITIALIZER(swtailq);
static struct swdevt *swdevhd; /* Allocate from here next */
static int nswapdev; /* Number of swap devices */
int swap_pager_avail;
static int swdev_syscall_active = 0; /* serialize swap(on|off) */
static struct sx swdev_syscall_lock; /* serialize swap(on|off) */
static vm_ooffset_t swap_total;
SYSCTL_QUAD(_vm, OID_AUTO, swap_total, CTLFLAG_RD, &swap_total, 0,
@ -487,6 +487,7 @@ swap_pager_init(void)
TAILQ_INIT(&swap_pager_object_list[i]);
mtx_init(&sw_alloc_mtx, "swap_pager list", NULL, MTX_DEF);
mtx_init(&sw_dev_mtx, "swapdev", NULL, MTX_DEF);
sx_init(&swdev_syscall_lock, "swsysc");
/*
* Device Stripe, in PAGE_SIZE'd blocks
@ -1664,7 +1665,7 @@ swap_pager_swapoff(struct swdevt *sp)
struct swblock *swap;
int i, j, retries;
GIANT_REQUIRED;
sx_assert(&swdev_syscall_lock, SA_XLOCKED);
retries = 0;
full_rescan:
@ -2005,10 +2006,7 @@ sys_swapon(struct thread *td, struct swapon_args *uap)
if (error)
return (error);
mtx_lock(&Giant);
while (swdev_syscall_active)
tsleep(&swdev_syscall_active, PUSER - 1, "swpon", 0);
swdev_syscall_active = 1;
sx_xlock(&swdev_syscall_lock);
/*
* Swap metadata may not fit in the KVM if we have physical
@ -2043,9 +2041,7 @@ sys_swapon(struct thread *td, struct swapon_args *uap)
if (error)
vrele(vp);
done:
swdev_syscall_active = 0;
wakeup_one(&swdev_syscall_active);
mtx_unlock(&Giant);
sx_xunlock(&swdev_syscall_lock);
return (error);
}
@ -2175,10 +2171,7 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap)
if (error)
return (error);
mtx_lock(&Giant);
while (swdev_syscall_active)
tsleep(&swdev_syscall_active, PUSER - 1, "swpoff", 0);
swdev_syscall_active = 1;
sx_xlock(&swdev_syscall_lock);
NDINIT(&nd, LOOKUP, FOLLOW | AUDITVNODE1, UIO_USERSPACE, uap->name,
td);
@ -2200,9 +2193,7 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap)
}
error = swapoff_one(sp, td->td_ucred);
done:
swdev_syscall_active = 0;
wakeup_one(&swdev_syscall_active);
mtx_unlock(&Giant);
sx_xunlock(&swdev_syscall_lock);
return (error);
}
@ -2214,7 +2205,7 @@ swapoff_one(struct swdevt *sp, struct ucred *cred)
int error;
#endif
mtx_assert(&Giant, MA_OWNED);
sx_assert(&swdev_syscall_lock, SA_XLOCKED);
#ifdef MAC
(void) vn_lock(sp->sw_vp, LK_EXCLUSIVE | LK_RETRY);
error = mac_system_check_swapoff(cred, sp->sw_vp);
@ -2276,10 +2267,7 @@ swapoff_all(void)
const char *devname;
int error;
mtx_lock(&Giant);
while (swdev_syscall_active)
tsleep(&swdev_syscall_active, PUSER - 1, "swpoff", 0);
swdev_syscall_active = 1;
sx_xlock(&swdev_syscall_lock);
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH_SAFE(sp, &swtailq, sw_list, spt) {
@ -2299,9 +2287,7 @@ swapoff_all(void)
}
mtx_unlock(&sw_dev_mtx);
swdev_syscall_active = 0;
wakeup_one(&swdev_syscall_active);
mtx_unlock(&Giant);
sx_xunlock(&swdev_syscall_lock);
}
void