Date: Sat, 22 Nov 2025 22:41:27 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Michal Meloun <mmel@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: mmap( MAP_ANON) is broken on current. (was Still seeing Failed assertion: "p[i] == 0" on armv7 buildworld) Message-ID: <aSIf9zLhTMVcK5Sj@kib.kiev.ua> In-Reply-To: <aSIa1Xt47HHMyDQ1@kib.kiev.ua> References: <aSG_GJNR7L4Mx-e8@kib.kiev.ua> <aSHDPDsuG40k2TEZ@kib.kiev.ua> <603e75f8-7064-4fca-8520-282331c20ec0@freebsd.org> <aSHZiASbyd4rqPIV@kib.kiev.ua> <b94a8938-91e5-41da-9686-03a62ab0142f@freebsd.org> <aSHqezcjIEXHeaIf@kib.kiev.ua> <f3350539-8dca-4d95-810a-f76c7daa7b89@freebsd.org> <aSIEzLFD2Xv7GD_a@kib.kiev.ua> <9a864c53-0033-46d1-ad07-6b528115789f@freebsd.org> <aSIa1Xt47HHMyDQ1@kib.kiev.ua>
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On Sat, Nov 22, 2025 at 10:19:38PM +0200, Konstantin Belousov wrote:
> Please in addition to the patch, enable debug.vm_check_pg_zero.
And use the following patch (one more hunk for vm_object_page_remove()):
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 6b09552c5fee..76808b5ad7f1 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -1743,6 +1743,27 @@ vm_map_insert1(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
(vm_size_t)(prev_entry->end - prev_entry->start),
(vm_size_t)(end - prev_entry->end), cred != NULL &&
(protoeflags & MAP_ENTRY_NEEDS_COPY) == 0)) {
+ vm_object_t obj = prev_entry->object.vm_object;
+ if (obj != NULL) {
+ struct pctrie_iter pages;
+ vm_page_t p;
+
+ vm_page_iter_init(&pages, obj);
+ p = vm_radix_iter_lookup_ge(&pages,
+ OFF_TO_IDX(prev_entry->offset +
+ prev_entry->end - prev_entry->start));
+ if (p != NULL) {
+ KASSERT(p->pindex >= OFF_TO_IDX(prev_entry->offset +
+ prev_entry->end - prev_entry->start +
+ end - start),
+ ("FOUND page %p pindex %#jx "
+ "e %#jx %#jx %#jx %#jx",
+ p, p->pindex, (uintmax_t)prev_entry->offset,
+ (uintmax_t)prev_entry->end,
+ (uintmax_t)prev_entry->start,
+ (uintmax_t)(end - start)));
+ }
+ }
/*
* We were able to extend the object. Determine if we
* can extend the previous map entry to include the
diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 5b4517d2bf0c..e87047f9a380 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -1988,7 +1988,7 @@ vm_object_page_remove(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
(options & (OBJPR_CLEANONLY | OBJPR_NOTMAPPED)) == OBJPR_NOTMAPPED,
("vm_object_page_remove: illegal options for object %p", object));
if (object->resident_page_count == 0)
- return;
+ goto remove_pager;
vm_object_pip_add(object, 1);
vm_page_iter_limit_init(&pages, object, end);
again:
@@ -2061,6 +2061,7 @@ vm_object_page_remove(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
}
vm_object_pip_wakeup(object);
+remove_pager:
vm_pager_freespace(object, start, (end == 0 ? object->size : end) -
start);
}
@@ -2189,13 +2190,19 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
next_size >>= PAGE_SHIFT;
next_pindex = OFF_TO_IDX(prev_offset) + prev_size;
- if (prev_object->ref_count > 1 &&
- prev_object->size != next_pindex &&
+ if (prev_object->ref_count > 1 ||
+ prev_object->size != next_pindex ||
(prev_object->flags & OBJ_ONEMAPPING) == 0) {
VM_OBJECT_WUNLOCK(prev_object);
return (FALSE);
}
+ KASSERT(next_pindex + next_size > prev_object->size,
+ ("vm_object_coalesce: "
+ "obj %p next_pindex %#jx next_size %#jx obj_size %#jx",
+ prev_object, (uintmax_t)next_pindex, (uintmax_t)next_size,
+ (uintmax_t)prev_object->size));
+
/*
* Account for the charge.
*/
@@ -2222,26 +2229,13 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
* Remove any pages that may still be in the object from a previous
* deallocation.
*/
- if (next_pindex < prev_object->size) {
- vm_object_page_remove(prev_object, next_pindex, next_pindex +
- next_size, 0);
-#if 0
- if (prev_object->cred != NULL) {
- KASSERT(prev_object->charge >=
- ptoa(prev_object->size - next_pindex),
- ("object %p overcharged 1 %jx %jx", prev_object,
- (uintmax_t)next_pindex, (uintmax_t)next_size));
- prev_object->charge -= ptoa(prev_object->size -
- next_pindex);
- }
-#endif
- }
+ vm_object_page_remove(prev_object, next_pindex, next_pindex +
+ next_size, 0);
/*
* Extend the object if necessary.
*/
- if (next_pindex + next_size > prev_object->size)
- prev_object->size = next_pindex + next_size;
+ prev_object->size = next_pindex + next_size;
VM_OBJECT_WUNLOCK(prev_object);
return (TRUE);
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