Implement global and per-uid accounting of the anonymous memory. Add

rlimit RLIMIT_SWAP that limits the amount of swap that may be reserved
for the uid.

The accounting information (charge) is associated with either map entry,
or vm object backing the entry, assuming the object is the first one
in the shadow chain and entry does not require COW. Charge is moved
from entry to object on allocation of the object, e.g. during the mmap,
assuming the object is allocated, or on the first page fault on the
entry. It moves back to the entry on forks due to COW setup.

The per-entry granularity of accounting makes the charge process fair
for processes that change uid during lifetime, and decrements charge
for proper uid when region is unmapped.

The interface of vm_pager_allocate(9) is extended by adding struct ucred *,
that is used to charge appropriate uid when allocation if performed by
kernel, e.g. md(4).

Several syscalls, among them is fork(2), may now return ENOMEM when
global or per-uid limits are enforced.

In collaboration with:	pho
Reviewed by:	alc
Approved by:	re (kensmith)

1 files changed, 16 insertions, 2 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 721d48d..bfa43a9 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -214,6 +214,7 @@ fork1(td, flags, pages, procp)
 	struct thread *td2;
 	struct sigacts *newsigacts;
 	struct vmspace *vm2;
+	vm_ooffset_t mem_charged;
 	int error;
 
 	/* Can't copy and clear. */
@@ -274,6 +275,7 @@ norfproc_fail:
 	 * however it proved un-needed and caused problems
 	 */
 
+	mem_charged = 0;
 	vm2 = NULL;
 	/* Allocate new proc. */
 	newproc = uma_zalloc(proc_zone, M_WAITOK);
@@ -295,12 +297,24 @@ norfproc_fail:
 		}
 	}
 	if ((flags & RFMEM) == 0) {
-		vm2 = vmspace_fork(p1->p_vmspace);
+		vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
 		if (vm2 == NULL) {
 			error = ENOMEM;
 			goto fail1;
 		}
-	}
+		if (!swap_reserve(mem_charged)) {
+			/*
+			 * The swap reservation failed. The accounting
+			 * from the entries of the copied vm2 will be
+			 * substracted in vmspace_free(), so force the
+			 * reservation there.
+			 */
+			swap_reserve_force(mem_charged);
+			error = ENOMEM;
+			goto fail1;
+		}
+	} else
+		vm2 = NULL;
 #ifdef MAC
 	mac_proc_init(newproc);
 #endif