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kernel/vm: Use 64-bit signed types explicitly for memory computations.

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off_t is a signed 64-bit type, but size_t isn't signed or 64-bit
on 32-bit platforms. That meant adding a sign bit caused strange
things to happen there.

Fixes incorrect free-memory computations on 32-bit.
(cherry picked from commit cc565c81afd2dfba34de6ced607199d757080a8d)

Change-Id: I294f92ac1279a6311347b5e25341542d8c862013
Reviewed-on: https://review.haiku-os.org/c/haiku/+/11326
Reviewed-by: waddlesplash <[email protected]>
This commit is contained in:
Augustin Cavalier
2026-07-22 17:37:42 +00:00
committed by waddlesplash
parent 0178ddbc88
commit 9d80b76b46
1 changed files with 7 additions and 7 deletions
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src/system/kernel/vm/vm.cpp
+7 -7
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@@ -250,11 +250,11 @@ static uint32 sPageMappingsMask;
static rw_lock sAreaCacheLock = RW_LOCK_INITIALIZER("area->cache"); static rw_lock sAreaCacheLock = RW_LOCK_INITIALIZER("area->cache");
static rw_spinlock sAvailableMemoryLock = B_RW_SPINLOCK_INITIALIZER; static rw_spinlock sAvailableMemoryLock = B_RW_SPINLOCK_INITIALIZER;
static off_t sAvailableMemory; static int64 sAvailableMemory;
#if ENABLE_SWAP_SUPPORT #if ENABLE_SWAP_SUPPORT
static off_t sAvailableMemoryAndSwap; static int64 sAvailableMemoryAndSwap;
#endif #endif
static off_t sNeededMemory; static int64 sNeededMemory;
static uint32 sPageFaults; static uint32 sPageFaults;
static VMPhysicalPageMapper* sPhysicalPageMapper; static VMPhysicalPageMapper* sPhysicalPageMapper;
@@ -4432,20 +4432,20 @@ vm_unreserve_memory_or_swap(size_t amount)
static status_t static status_t
vm_try_reserve_internal(off_t& pool, uint32 resource, vm_try_reserve_internal(int64& pool, uint32 resource,
size_t amount, int priority, bigtime_t absoluteTimeout) int64 amount, int priority, bigtime_t absoluteTimeout)
{ {
ASSERT((amount % B_PAGE_SIZE) == 0); ASSERT((amount % B_PAGE_SIZE) == 0);
ASSERT(priority >= 0 && priority < (int)B_COUNT_OF(kMemoryReserveForPriority)); ASSERT(priority >= 0 && priority < (int)B_COUNT_OF(kMemoryReserveForPriority));
TRACE(("try to reserve %lu bytes, %Lu left\n", amount, pool)); TRACE(("try to reserve %lu bytes, %Lu left\n", amount, pool));
const size_t reserve = kMemoryReserveForPriority[priority]; const size_t reserve = kMemoryReserveForPriority[priority];
const off_t amountPlusReserve = amount + reserve; const int64 amountPlusReserve = amount + reserve;
// Try with a read-lock and atomics first, but only if there's more than double // Try with a read-lock and atomics first, but only if there's more than double
// the amount of memory we're trying to reserve available, to avoid races. // the amount of memory we're trying to reserve available, to avoid races.
InterruptsReadSpinLocker readLocker(sAvailableMemoryLock); InterruptsReadSpinLocker readLocker(sAvailableMemoryLock);
if (atomic_get64(&pool) > (off_t)(amountPlusReserve + amount)) { if (atomic_get64(&pool) > (amountPlusReserve + amount)) {
if (atomic_add64(&pool, -amount) >= amountPlusReserve) if (atomic_add64(&pool, -amount) >= amountPlusReserve)
return B_OK; return B_OK;