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swapoff(2): add a SWAPOFF_FORCE flag

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The flag requests skipping the heuristic which tries to avoid leaving
system with more allocated memory than available from RAM and remanining
swap.

Reviewed by:	markj
Discussed with:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D33165
This commit is contained in:
Konstantin Belousov 2021-11-29 18:28:19 +02:00
parent a4e4132fa3
commit e8dc2ba29c
2 changed files with 8 additions and 6 deletions
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12
sys/vm/swap_pager.c
View File

@ -470,7 +470,7 @@ static void swp_pager_free_empty_swblk(vm_object_t, struct swblk *sb);
static int swapongeom(struct vnode *);
static int swaponvp(struct thread *, struct vnode *, u_long);
static int swapoff_one(struct swdevt *sp, struct ucred *cred,
bool ignore_check);
u_int flags);
/*
* Swap bitmap functions
@ -2511,7 +2511,7 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap)
error = copyin(uap->name, &sa, sizeof(sa));
if (error != 0)
return (error);
if (sa.flags != 0)
if ((sa.flags & ~(SWAPOFF_FORCE)) != 0)
return (EINVAL);
break;
default:
@ -2539,14 +2539,14 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap)
error = EINVAL;
goto done;
}
error = swapoff_one(sp, td->td_ucred, false);
error = swapoff_one(sp, td->td_ucred, sa.flags);
done:
sx_xunlock(&swdev_syscall_lock);
return (error);
}
static int
swapoff_one(struct swdevt *sp, struct ucred *cred, bool ignore_check)
swapoff_one(struct swdevt *sp, struct ucred *cred, u_int flags)
{
u_long nblks;
#ifdef MAC
@ -2576,7 +2576,7 @@ swapoff_one(struct swdevt *sp, struct ucred *cred, bool ignore_check)
* means that we can lose swap data when filesystems go away,
* which is arguably worse.
*/
if (!ignore_check &&
if ((flags & SWAPOFF_FORCE) == 0 &&
vm_free_count() + swap_pager_avail < nblks + nswap_lowat)
return (ENOMEM);
@ -2627,7 +2627,7 @@ swapoff_all(void)
devname = devtoname(sp->sw_vp->v_rdev);
else
devname = "[file]";
error = swapoff_one(sp, thread0.td_ucred, true);
error = swapoff_one(sp, thread0.td_ucred, SWAPOFF_FORCE);
if (error != 0) {
printf("Cannot remove swap device %s (error=%d), "
"skipping.\n", devname, error);

2
sys/vm/swap_pager.h
View File

@ -77,6 +77,8 @@ struct swapoff_new_args {
uintptr_t pad1[8];
};
#define SWAPOFF_FORCE 0x00000001
#ifdef _KERNEL
extern int swap_pager_avail;