diff options
| author | Konstantin Belousov <kib@FreeBSD.org> | 2025-11-27 21:53:24 +0000 |
|---|---|---|
| committer | Konstantin Belousov <kib@FreeBSD.org> | 2025-12-30 03:25:36 +0000 |
| commit | 353ba3bf08fdef69b77e3e565435e50784a51412 (patch) | |
| tree | 48a2f4ae363df931eac92ad14b021e1f81eed778 | |
| parent | e7053d9a126a60b3c0b1348b6c5131b5f2025894 (diff) | |
vm_object_coalesce(): do not account holes twice
alc wrote:
Suppose that the object is OBJ_ONEMAPPING and that we, in fact,
have a single mapping to it. Then, we punch a hole in that mapping.
vm_map_entry_delete() only subtracts from the object's charge when
we shrink the size of the object. Now, suppose that we perform
mmap(MAP_ANON) to reallocate some of the hole. Aren't we going to add to
the charge here, even though vm_map_entry_delete() never subtracted from
the charge for the hole that was created?
Only account the change in the charged object size that was added to it.
Noted by: alc
Reviewed by: alc, markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D54263
| -rw-r--r-- | sys/vm/vm_object.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c index 36edb279bbce..c216fdc01af1 100644 --- a/sys/vm/vm_object.c +++ b/sys/vm/vm_object.c @@ -2202,7 +2202,8 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset, /* * Account for the charge. */ - if (prev_object->cred != NULL) { + if (prev_object->cred != NULL && + next_pindex + next_size > prev_object->size) { /* * If prev_object was charged, then this mapping, * although not charged now, may become writable @@ -2213,12 +2214,14 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset, * entry, and swap reservation for this entry is * managed in appropriate time. */ - if (!reserved && !swap_reserve_by_cred(ptoa(next_size), - prev_object->cred)) { + vm_size_t charge = ptoa(next_pindex + next_size - + prev_object->size); + if (!reserved && + !swap_reserve_by_cred(charge, prev_object->cred)) { VM_OBJECT_WUNLOCK(prev_object); return (FALSE); } - prev_object->charge += ptoa(next_size); + prev_object->charge += charge; } /* |