The branch stable/13 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=08d995ca8f6f1008a10e4bf4d924824c040f842a
commit 08d995ca8f6f1008a10e4bf4d924824c040f842a Author: Konstantin Belousov <[email protected]> AuthorDate: 2021-11-26 23:22:27 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2021-12-06 00:29:43 +0000 swapoff_one(): only check free pages count manually turning swap off (cherry picked from commit 0190c38b9dfaa16de1bc61e829b9a1221fed7896) --- sys/vm/swap_pager.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c index 78533c9fb5e6..473d950dafbf 100644 --- a/sys/vm/swap_pager.c +++ b/sys/vm/swap_pager.c @@ -469,7 +469,8 @@ static bool swp_pager_swblk_empty(struct swblk *sb, int start, int limit); 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); +static int swapoff_one(struct swdevt *sp, struct ucred *cred, + bool ignore_check); /* * Swap bitmap functions @@ -2518,14 +2519,14 @@ sys_swapoff(struct thread *td, struct swapoff_args *uap) error = EINVAL; goto done; } - error = swapoff_one(sp, td->td_ucred); + error = swapoff_one(sp, td->td_ucred, false); done: sx_xunlock(&swdev_syscall_lock); return (error); } static int -swapoff_one(struct swdevt *sp, struct ucred *cred) +swapoff_one(struct swdevt *sp, struct ucred *cred, bool ignore_check) { u_long nblks; #ifdef MAC @@ -2547,8 +2548,16 @@ swapoff_one(struct swdevt *sp, struct ucred *cred) * available virtual memory in the system will fit the amount * of data we will have to page back in, plus an epsilon so * the system doesn't become critically low on swap space. + * The vm_free_count() part does not account e.g. for clean + * pages that can be immediately reclaimed without paging, so + * this is a very rough estimation. + * + * On the other hand, not turning swap off on swapoff_all() + * means that we can lose swap data when filesystems go away, + * which is arguably worse. */ - if (vm_free_count() + swap_pager_avail < nblks + nswap_lowat) + if (!ignore_check && + vm_free_count() + swap_pager_avail < nblks + nswap_lowat) return (ENOMEM); /* @@ -2598,7 +2607,7 @@ swapoff_all(void) devname = devtoname(sp->sw_vp->v_rdev); else devname = "[file]"; - error = swapoff_one(sp, thread0.td_ucred); + error = swapoff_one(sp, thread0.td_ucred, true); if (error != 0) { printf("Cannot remove swap device %s (error=%d), " "skipping.\n", devname, error);
