btrfs: Attempt to fix GCC2 build.

[haiku.git] / src / system / kernel / vm / VMAnonymousCache.cpp

/*
 * Copyright 2008, Zhao Shuai, upczhsh@163.com.
 * Copyright 2008-2011, Ingo Weinhold, ingo_weinhold@gmx.de.
 * Copyright 2002-2009, Axel Dörfler, axeld@pinc-software.de.
 * Distributed under the terms of the MIT License.
 *
 * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
 * Distributed under the terms of the NewOS License.
 *
 * Copyright 2011-2012 Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *              Hamish Morrison, hamish@lavabit.com
 *              Alexander von Gluck IV, kallisti5@unixzen.com
 */


#include "VMAnonymousCache.h"

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <FindDirectory.h>
#include <KernelExport.h>
#include <NodeMonitor.h>

#include <arch_config.h>
#include <boot_device.h>
#include <disk_device_manager/KDiskDevice.h>
#include <disk_device_manager/KDiskDeviceManager.h>
#include <disk_device_manager/KDiskSystem.h>
#include <disk_device_manager/KPartitionVisitor.h>
#include <driver_settings.h>
#include <fs/fd.h>
#include <fs/KPath.h>
#include <fs_info.h>
#include <fs_interface.h>
#include <heap.h>
#include <kernel_daemon.h>
#include <slab/Slab.h>
#include <syscalls.h>
#include <system_info.h>
#include <tracing.h>
#include <util/AutoLock.h>
#include <util/DoublyLinkedList.h>
#include <util/OpenHashTable.h>
#include <util/RadixBitmap.h>
#include <vfs.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_priv.h>
#include <vm/VMAddressSpace.h>

#include "IORequest.h"


#if     ENABLE_SWAP_SUPPORT

//#define TRACE_VM_ANONYMOUS_CACHE
#ifdef TRACE_VM_ANONYMOUS_CACHE
#       define TRACE(x...) dprintf(x)
#else
#       define TRACE(x...) do { } while (false)
#endif


// number of free swap blocks the object cache shall minimally have
#define MIN_SWAP_BLOCK_RESERVE  4096

// interval the has resizer is triggered (in 0.1s)
#define SWAP_HASH_RESIZE_INTERVAL       5

#define INITIAL_SWAP_HASH_SIZE          1024

#define SWAP_SLOT_NONE  RADIX_SLOT_NONE

#define SWAP_BLOCK_PAGES 32
#define SWAP_BLOCK_SHIFT 5              /* 1 << SWAP_BLOCK_SHIFT == SWAP_BLOCK_PAGES */
#define SWAP_BLOCK_MASK  (SWAP_BLOCK_PAGES - 1)


static const char* const kDefaultSwapPath = "/var/swap";

struct swap_file : DoublyLinkedListLinkImpl<swap_file> {
        int                             fd;
        struct vnode*   vnode;
        void*                   cookie;
        swap_addr_t             first_slot;
        swap_addr_t             last_slot;
        radix_bitmap*   bmp;
};

struct swap_hash_key {
        VMAnonymousCache        *cache;
        off_t                           page_index;  // page index in the cache
};

// Each swap block contains swap address information for
// SWAP_BLOCK_PAGES continuous pages from the same cache
struct swap_block {
        swap_block*             hash_link;
        swap_hash_key   key;
        uint32                  used;
        swap_addr_t             swap_slots[SWAP_BLOCK_PAGES];
};

struct SwapHashTableDefinition {
        typedef swap_hash_key KeyType;
        typedef swap_block ValueType;

        SwapHashTableDefinition() {}

        size_t HashKey(const swap_hash_key& key) const
        {
                off_t blockIndex = key.page_index >> SWAP_BLOCK_SHIFT;
                VMAnonymousCache* cache = key.cache;
                return blockIndex ^ (size_t)(int*)cache;
        }

        size_t Hash(const swap_block* value) const
        {
                return HashKey(value->key);
        }

        bool Compare(const swap_hash_key& key, const swap_block* value) const
        {
                return (key.page_index & ~(off_t)SWAP_BLOCK_MASK)
                                == (value->key.page_index & ~(off_t)SWAP_BLOCK_MASK)
                        && key.cache == value->key.cache;
        }

        swap_block*& GetLink(swap_block* value) const
        {
                return value->hash_link;
        }
};

typedef BOpenHashTable<SwapHashTableDefinition> SwapHashTable;
typedef DoublyLinkedList<swap_file> SwapFileList;

static SwapHashTable sSwapHashTable;
static rw_lock sSwapHashLock;

static SwapFileList sSwapFileList;
static mutex sSwapFileListLock;
static swap_file* sSwapFileAlloc = NULL; // allocate from here
static uint32 sSwapFileCount = 0;

static off_t sAvailSwapSpace = 0;
static mutex sAvailSwapSpaceLock;

static object_cache* sSwapBlockCache;


#if SWAP_TRACING
namespace SwapTracing {

class SwapTraceEntry : public AbstractTraceEntry {
public:
        SwapTraceEntry(VMAnonymousCache* cache)
                :
                fCache(cache)
        {
        }

protected:
        VMAnonymousCache*       fCache;
};


class ReadPage : public SwapTraceEntry {
public:
        ReadPage(VMAnonymousCache* cache, page_num_t pageIndex,
                swap_addr_t swapSlotIndex)
                :
                SwapTraceEntry(cache),
                fPageIndex(pageIndex),
                fSwapSlotIndex(swapSlotIndex)
        {
                Initialized();
        }

        virtual void AddDump(TraceOutput& out)
        {
                out.Print("swap read:  cache %p, page index: %lu <- swap slot: %lu",
                        fCache, fPageIndex, fSwapSlotIndex);
        }

private:
        page_num_t              fPageIndex;
        swap_addr_t             fSwapSlotIndex;
};


class WritePage : public SwapTraceEntry {
public:
        WritePage(VMAnonymousCache* cache, page_num_t pageIndex,
                swap_addr_t swapSlotIndex)
                :
                SwapTraceEntry(cache),
                fPageIndex(pageIndex),
                fSwapSlotIndex(swapSlotIndex)
        {
                Initialized();
        }

        virtual void AddDump(TraceOutput& out)
        {
                out.Print("swap write: cache %p, page index: %lu -> swap slot: %lu",
                        fCache, fPageIndex, fSwapSlotIndex);
        }

private:
        page_num_t              fPageIndex;
        swap_addr_t             fSwapSlotIndex;
};

}       // namespace SwapTracing

#       define T(x) new(std::nothrow) SwapTracing::x;
#else
#       define T(x) ;
#endif


static int
dump_swap_info(int argc, char** argv)
{
        swap_addr_t totalSwapPages = 0;
        swap_addr_t freeSwapPages = 0;

        kprintf("swap files:\n");

        for (SwapFileList::Iterator it = sSwapFileList.GetIterator();
                swap_file* file = it.Next();) {
                swap_addr_t total = file->last_slot - file->first_slot;
                kprintf("  vnode: %p, pages: total: %" B_PRIu32 ", free: %" B_PRIu32
                        "\n", file->vnode, total, file->bmp->free_slots);

                totalSwapPages += total;
                freeSwapPages += file->bmp->free_slots;
        }

        kprintf("\n");
        kprintf("swap space in pages:\n");
        kprintf("total:     %9" B_PRIu32 "\n", totalSwapPages);
        kprintf("available: %9" B_PRIdOFF "\n", sAvailSwapSpace / B_PAGE_SIZE);
        kprintf("reserved:  %9" B_PRIdOFF "\n",
                totalSwapPages - sAvailSwapSpace / B_PAGE_SIZE);
        kprintf("used:      %9" B_PRIu32 "\n", totalSwapPages - freeSwapPages);
        kprintf("free:      %9" B_PRIu32 "\n", freeSwapPages);

        return 0;
}


static swap_addr_t
swap_slot_alloc(uint32 count)
{
        mutex_lock(&sSwapFileListLock);

        if (sSwapFileList.IsEmpty()) {
                mutex_unlock(&sSwapFileListLock);
                panic("swap_slot_alloc(): no swap file in the system\n");
                return SWAP_SLOT_NONE;
        }

        // since radix bitmap could not handle more than 32 pages, we return
        // SWAP_SLOT_NONE, this forces Write() adjust allocation amount
        if (count > BITMAP_RADIX) {
                mutex_unlock(&sSwapFileListLock);
                return SWAP_SLOT_NONE;
        }

        swap_addr_t j, addr = SWAP_SLOT_NONE;
        for (j = 0; j < sSwapFileCount; j++) {
                if (sSwapFileAlloc == NULL)
                        sSwapFileAlloc = sSwapFileList.First();

                addr = radix_bitmap_alloc(sSwapFileAlloc->bmp, count);
                if (addr != SWAP_SLOT_NONE) {
                        addr += sSwapFileAlloc->first_slot;
                        break;
                }

                // this swap_file is full, find another
                sSwapFileAlloc = sSwapFileList.GetNext(sSwapFileAlloc);
        }

        if (j == sSwapFileCount) {
                mutex_unlock(&sSwapFileListLock);
                panic("swap_slot_alloc: swap space exhausted!\n");
                return SWAP_SLOT_NONE;
        }

        // if this swap file has used more than 90% percent of its space
        // switch to another
        if (sSwapFileAlloc->bmp->free_slots
                < (sSwapFileAlloc->last_slot - sSwapFileAlloc->first_slot) / 10) {
                sSwapFileAlloc = sSwapFileList.GetNext(sSwapFileAlloc);
        }

        mutex_unlock(&sSwapFileListLock);

        return addr;
}


static swap_file*
find_swap_file(swap_addr_t slotIndex)
{
        for (SwapFileList::Iterator it = sSwapFileList.GetIterator();
                swap_file* swapFile = it.Next();) {
                if (slotIndex >= swapFile->first_slot
                        && slotIndex < swapFile->last_slot) {
                        return swapFile;
                }
        }

        panic("find_swap_file(): can't find swap file for slot %" B_PRIu32 "\n",
                slotIndex);
        return NULL;
}


static void
swap_slot_dealloc(swap_addr_t slotIndex, uint32 count)
{
        if (slotIndex == SWAP_SLOT_NONE)
                return;

        mutex_lock(&sSwapFileListLock);
        swap_file* swapFile = find_swap_file(slotIndex);
        slotIndex -= swapFile->first_slot;
        radix_bitmap_dealloc(swapFile->bmp, slotIndex, count);
        mutex_unlock(&sSwapFileListLock);
}


static off_t
swap_space_reserve(off_t amount)
{
        mutex_lock(&sAvailSwapSpaceLock);
        if (sAvailSwapSpace >= amount)
                sAvailSwapSpace -= amount;
        else {
                amount = sAvailSwapSpace;
                sAvailSwapSpace = 0;
        }
        mutex_unlock(&sAvailSwapSpaceLock);

        return amount;
}


static void
swap_space_unreserve(off_t amount)
{
        mutex_lock(&sAvailSwapSpaceLock);
        sAvailSwapSpace += amount;
        mutex_unlock(&sAvailSwapSpaceLock);
}


static void
swap_hash_resizer(void*, int)
{
        WriteLocker locker(sSwapHashLock);

        size_t size;
        void* allocation;

        do {
                size = sSwapHashTable.ResizeNeeded();
                if (size == 0)
                        return;

                locker.Unlock();

                allocation = malloc(size);
                if (allocation == NULL)
                        return;

                locker.Lock();

        } while (!sSwapHashTable.Resize(allocation, size));
}


// #pragma mark -


class VMAnonymousCache::WriteCallback : public StackableAsyncIOCallback {
public:
        WriteCallback(VMAnonymousCache* cache, AsyncIOCallback* callback)
                :
                StackableAsyncIOCallback(callback),
                fCache(cache)
        {
        }

        void SetTo(page_num_t pageIndex, swap_addr_t slotIndex, bool newSlot)
        {
                fPageIndex = pageIndex;
                fSlotIndex = slotIndex;
                fNewSlot = newSlot;
        }

        virtual void IOFinished(status_t status, bool partialTransfer,
                generic_size_t bytesTransferred)
        {
                if (fNewSlot) {
                        if (status == B_OK) {
                                fCache->_SwapBlockBuild(fPageIndex, fSlotIndex, 1);
                        } else {
                                AutoLocker<VMCache> locker(fCache);
                                fCache->fAllocatedSwapSize -= B_PAGE_SIZE;
                                locker.Unlock();

                                swap_slot_dealloc(fSlotIndex, 1);
                        }
                }

                fNextCallback->IOFinished(status, partialTransfer, bytesTransferred);

                delete this;
        }

private:
        VMAnonymousCache*       fCache;
        page_num_t                      fPageIndex;
        swap_addr_t                     fSlotIndex;
        bool                            fNewSlot;
};


// #pragma mark -


VMAnonymousCache::~VMAnonymousCache()
{
        // free allocated swap space and swap block
        for (off_t offset = virtual_base, toFree = fAllocatedSwapSize;
                offset < virtual_end && toFree > 0; offset += B_PAGE_SIZE) {
                swap_addr_t slotIndex = _SwapBlockGetAddress(offset >> PAGE_SHIFT);
                if (slotIndex == SWAP_SLOT_NONE)
                        continue;

                swap_slot_dealloc(slotIndex, 1);
                _SwapBlockFree(offset >> PAGE_SHIFT, 1);
                toFree -= B_PAGE_SIZE;
        }

        swap_space_unreserve(fCommittedSwapSize);
        if (committed_size > fCommittedSwapSize)
                vm_unreserve_memory(committed_size - fCommittedSwapSize);
}


status_t
VMAnonymousCache::Init(bool canOvercommit, int32 numPrecommittedPages,
        int32 numGuardPages, uint32 allocationFlags)
{
        TRACE("%p->VMAnonymousCache::Init(canOvercommit = %s, "
                "numPrecommittedPages = %" B_PRId32 ", numGuardPages = %" B_PRId32
                ")\n", this, canOvercommit ? "yes" : "no", numPrecommittedPages,
                numGuardPages);

        status_t error = VMCache::Init(CACHE_TYPE_RAM, allocationFlags);
        if (error != B_OK)
                return error;

        fCanOvercommit = canOvercommit;
        fHasPrecommitted = false;
        fPrecommittedPages = min_c(numPrecommittedPages, 255);
        fGuardedSize = numGuardPages * B_PAGE_SIZE;
        fCommittedSwapSize = 0;
        fAllocatedSwapSize = 0;

        return B_OK;
}


status_t
VMAnonymousCache::Resize(off_t newSize, int priority)
{
        // If the cache size shrinks, drop all swap pages beyond the new size.
        if (fAllocatedSwapSize > 0) {
                off_t oldPageCount = (virtual_end + B_PAGE_SIZE - 1) >> PAGE_SHIFT;
                swap_block* swapBlock = NULL;

                for (off_t pageIndex = (newSize + B_PAGE_SIZE - 1) >> PAGE_SHIFT;
                        pageIndex < oldPageCount && fAllocatedSwapSize > 0; pageIndex++) {

                        WriteLocker locker(sSwapHashLock);

                        // Get the swap slot index for the page.
                        swap_addr_t blockIndex = pageIndex & SWAP_BLOCK_MASK;
                        if (swapBlock == NULL || blockIndex == 0) {
                                swap_hash_key key = { this, pageIndex };
                                swapBlock = sSwapHashTable.Lookup(key);

                                if (swapBlock == NULL) {
                                        pageIndex = ROUNDUP(pageIndex + 1, SWAP_BLOCK_PAGES);
                                        continue;
                                }
                        }

                        swap_addr_t slotIndex = swapBlock->swap_slots[blockIndex];
                        vm_page* page;
                        if (slotIndex != SWAP_SLOT_NONE
                                && ((page = LookupPage((off_t)pageIndex * B_PAGE_SIZE)) == NULL
                                        || !page->busy)) {
                                        // TODO: We skip (i.e. leak) swap space of busy pages, since
                                        // there could be I/O going on (paging in/out). Waiting is
                                        // not an option as 1. unlocking the cache means that new
                                        // swap pages could be added in a range we've already
                                        // cleared (since the cache still has the old size) and 2.
                                        // we'd risk a deadlock in case we come from the file cache
                                        // and the FS holds the node's write-lock. We should mark
                                        // the page invalid and let the one responsible clean up.
                                        // There's just no such mechanism yet.
                                swap_slot_dealloc(slotIndex, 1);
                                fAllocatedSwapSize -= B_PAGE_SIZE;

                                swapBlock->swap_slots[blockIndex] = SWAP_SLOT_NONE;
                                if (--swapBlock->used == 0) {
                                        // All swap pages have been freed -- we can discard the swap
                                        // block.
                                        sSwapHashTable.RemoveUnchecked(swapBlock);
                                        object_cache_free(sSwapBlockCache, swapBlock,
                                                CACHE_DONT_WAIT_FOR_MEMORY
                                                        | CACHE_DONT_LOCK_KERNEL_SPACE);
                                }
                        }
                }
        }

        return VMCache::Resize(newSize, priority);
}


status_t
VMAnonymousCache::Commit(off_t size, int priority)
{
        TRACE("%p->VMAnonymousCache::Commit(%" B_PRIdOFF ")\n", this, size);

        // If we can overcommit, we don't commit here, but in Fault(). We always
        // unreserve memory, if we're asked to shrink our commitment, though.
        if (fCanOvercommit && size > committed_size) {
                if (fHasPrecommitted)
                        return B_OK;

                // pre-commit some pages to make a later failure less probable
                fHasPrecommitted = true;
                uint32 precommitted = fPrecommittedPages * B_PAGE_SIZE;
                if (size > precommitted)
                        size = precommitted;
        }

        return _Commit(size, priority);
}


bool
VMAnonymousCache::HasPage(off_t offset)
{
        if (_SwapBlockGetAddress(offset >> PAGE_SHIFT) != SWAP_SLOT_NONE)
                return true;

        return false;
}


bool
VMAnonymousCache::DebugHasPage(off_t offset)
{
        off_t pageIndex = offset >> PAGE_SHIFT;
        swap_hash_key key = { this, pageIndex };
        swap_block* swap = sSwapHashTable.Lookup(key);
        if (swap == NULL)
                return false;

        return swap->swap_slots[pageIndex & SWAP_BLOCK_MASK] != SWAP_SLOT_NONE;
}


status_t
VMAnonymousCache::Read(off_t offset, const generic_io_vec* vecs, size_t count,
        uint32 flags, generic_size_t* _numBytes)
{
        off_t pageIndex = offset >> PAGE_SHIFT;

        for (uint32 i = 0, j = 0; i < count; i = j) {
                swap_addr_t startSlotIndex = _SwapBlockGetAddress(pageIndex + i);
                for (j = i + 1; j < count; j++) {
                        swap_addr_t slotIndex = _SwapBlockGetAddress(pageIndex + j);
                        if (slotIndex != startSlotIndex + j - i)
                                break;
                }

                T(ReadPage(this, pageIndex, startSlotIndex));
                        // TODO: Assumes that only one page is read.

                swap_file* swapFile = find_swap_file(startSlotIndex);

                off_t pos = (off_t)(startSlotIndex - swapFile->first_slot)
                        * B_PAGE_SIZE;

                status_t status = vfs_read_pages(swapFile->vnode, swapFile->cookie, pos,
                        vecs + i, j - i, flags, _numBytes);
                if (status != B_OK)
                        return status;
        }

        return B_OK;
}


status_t
VMAnonymousCache::Write(off_t offset, const generic_io_vec* vecs, size_t count,
        uint32 flags, generic_size_t* _numBytes)
{
        off_t pageIndex = offset >> PAGE_SHIFT;

        AutoLocker<VMCache> locker(this);

        page_num_t totalPages = 0;
        for (uint32 i = 0; i < count; i++) {
                page_num_t pageCount = (vecs[i].length + B_PAGE_SIZE - 1) >> PAGE_SHIFT;
                swap_addr_t slotIndex = _SwapBlockGetAddress(pageIndex + totalPages);
                if (slotIndex != SWAP_SLOT_NONE) {
                        swap_slot_dealloc(slotIndex, pageCount);
                        _SwapBlockFree(pageIndex + totalPages, pageCount);
                        fAllocatedSwapSize -= pageCount * B_PAGE_SIZE;
                }

                totalPages += pageCount;
        }

        off_t totalSize = totalPages * B_PAGE_SIZE;
        if (fAllocatedSwapSize + totalSize > fCommittedSwapSize)
                return B_ERROR;

        fAllocatedSwapSize += totalSize;
        locker.Unlock();

        page_num_t pagesLeft = totalPages;
        totalPages = 0;

        for (uint32 i = 0; i < count; i++) {
                page_num_t pageCount = (vecs[i].length + B_PAGE_SIZE - 1) >> PAGE_SHIFT;

                generic_addr_t vectorBase = vecs[i].base;
                generic_size_t vectorLength = vecs[i].length;
                page_num_t n = pageCount;

                for (page_num_t j = 0; j < pageCount; j += n) {
                        swap_addr_t slotIndex;
                        // try to allocate n slots, if fail, try to allocate n/2
                        while ((slotIndex = swap_slot_alloc(n)) == SWAP_SLOT_NONE && n >= 2)
                                n >>= 1;

                        if (slotIndex == SWAP_SLOT_NONE)
                                panic("VMAnonymousCache::Write(): can't allocate swap space\n");

                        T(WritePage(this, pageIndex, slotIndex));
                                // TODO: Assumes that only one page is written.

                        swap_file* swapFile = find_swap_file(slotIndex);

                        off_t pos = (off_t)(slotIndex - swapFile->first_slot) * B_PAGE_SIZE;

                        generic_size_t length = (phys_addr_t)n * B_PAGE_SIZE;
                        generic_io_vec vector[1];
                        vector->base = vectorBase;
                        vector->length = length;

                        status_t status = vfs_write_pages(swapFile->vnode, swapFile->cookie,
                                pos, vector, 1, flags, &length);
                        if (status != B_OK) {
                                locker.Lock();
                                fAllocatedSwapSize -= (off_t)pagesLeft * B_PAGE_SIZE;
                                locker.Unlock();

                                swap_slot_dealloc(slotIndex, n);
                                return status;
                        }

                        _SwapBlockBuild(pageIndex + totalPages, slotIndex, n);
                        pagesLeft -= n;

                        if (n != pageCount) {
                                vectorBase = vectorBase + n * B_PAGE_SIZE;
                                vectorLength -= n * B_PAGE_SIZE;
                        }
                }

                totalPages += pageCount;
        }

        ASSERT(pagesLeft == 0);
        return B_OK;
}


status_t
VMAnonymousCache::WriteAsync(off_t offset, const generic_io_vec* vecs,
        size_t count, generic_size_t numBytes, uint32 flags,
        AsyncIOCallback* _callback)
{
        // TODO: Currently this method is only used for single pages. Either make
        // more flexible use of it or change the interface!
        // This implementation relies on the current usage!
        ASSERT(count == 1);
        ASSERT(numBytes <= B_PAGE_SIZE);

        page_num_t pageIndex = offset >> PAGE_SHIFT;
        swap_addr_t slotIndex = _SwapBlockGetAddress(pageIndex);
        bool newSlot = slotIndex == SWAP_SLOT_NONE;

        // If the page doesn't have any swap space yet, allocate it.
        if (newSlot) {
                AutoLocker<VMCache> locker(this);
                if (fAllocatedSwapSize + B_PAGE_SIZE > fCommittedSwapSize) {
                        _callback->IOFinished(B_ERROR, true, 0);
                        return B_ERROR;
                }

                fAllocatedSwapSize += B_PAGE_SIZE;

                slotIndex = swap_slot_alloc(1);
        }

        // create our callback
        WriteCallback* callback = (flags & B_VIP_IO_REQUEST) != 0
                ? new(malloc_flags(HEAP_PRIORITY_VIP)) WriteCallback(this, _callback)
                : new(std::nothrow) WriteCallback(this, _callback);
        if (callback == NULL) {
                if (newSlot) {
                        AutoLocker<VMCache> locker(this);
                        fAllocatedSwapSize -= B_PAGE_SIZE;
                        locker.Unlock();

                        swap_slot_dealloc(slotIndex, 1);
                }
                _callback->IOFinished(B_NO_MEMORY, true, 0);
                return B_NO_MEMORY;
        }
        // TODO: If the page already had swap space assigned, we don't need an own
        // callback.

        callback->SetTo(pageIndex, slotIndex, newSlot);

        T(WritePage(this, pageIndex, slotIndex));

        // write the page asynchrounously
        swap_file* swapFile = find_swap_file(slotIndex);
        off_t pos = (off_t)(slotIndex - swapFile->first_slot) * B_PAGE_SIZE;

        return vfs_asynchronous_write_pages(swapFile->vnode, swapFile->cookie, pos,
                vecs, 1, numBytes, flags, callback);
}


bool
VMAnonymousCache::CanWritePage(off_t offset)
{
        // We can write the page, if we have not used all of our committed swap
        // space or the page already has a swap slot assigned.
        return fAllocatedSwapSize < fCommittedSwapSize
                || _SwapBlockGetAddress(offset >> PAGE_SHIFT) != SWAP_SLOT_NONE;
}


int32
VMAnonymousCache::MaxPagesPerAsyncWrite() const
{
        return 1;
}


status_t
VMAnonymousCache::Fault(struct VMAddressSpace* aspace, off_t offset)
{
        if (fGuardedSize > 0) {
                uint32 guardOffset;

#ifdef STACK_GROWS_DOWNWARDS
                guardOffset = 0;
#elif defined(STACK_GROWS_UPWARDS)
                guardOffset = virtual_size - fGuardedSize;
#else
#       error Stack direction has not been defined in arch_config.h
#endif
                // report stack fault, guard page hit!
                if (offset >= guardOffset && offset < guardOffset + fGuardedSize) {
                        TRACE(("stack overflow!\n"));
                        return B_BAD_ADDRESS;
                }
        }

        if (fCanOvercommit && LookupPage(offset) == NULL && !HasPage(offset)) {
                if (fPrecommittedPages == 0) {
                        // never commit more than needed
                        if (committed_size / B_PAGE_SIZE > page_count)
                                return B_BAD_HANDLER;

                        // try to commit additional swap space/memory
                        if (swap_space_reserve(B_PAGE_SIZE) == B_PAGE_SIZE) {
                                fCommittedSwapSize += B_PAGE_SIZE;
                        } else {
                                int priority = aspace == VMAddressSpace::Kernel()
                                        ? VM_PRIORITY_SYSTEM : VM_PRIORITY_USER;
                                if (vm_try_reserve_memory(B_PAGE_SIZE, priority, 0) != B_OK) {
                                        dprintf("%p->VMAnonymousCache::Fault(): Failed to reserve "
                                                "%d bytes of RAM.\n", this, (int)B_PAGE_SIZE);
                                        return B_NO_MEMORY;
                                }
                        }

                        committed_size += B_PAGE_SIZE;
                } else
                        fPrecommittedPages--;
        }

        // This will cause vm_soft_fault() to handle the fault
        return B_BAD_HANDLER;
}


void
VMAnonymousCache::Merge(VMCache* _source)
{
        VMAnonymousCache* source = dynamic_cast<VMAnonymousCache*>(_source);
        if (source == NULL) {
                panic("VMAnonymousCache::MergeStore(): merge with incompatible cache "
                        "%p requested", _source);
                return;
        }

        // take over the source' committed size
        fCommittedSwapSize += source->fCommittedSwapSize;
        source->fCommittedSwapSize = 0;
        committed_size += source->committed_size;
        source->committed_size = 0;

        off_t actualSize = virtual_end - virtual_base;
        if (committed_size > actualSize)
                _Commit(actualSize, VM_PRIORITY_USER);

        // Move all not shadowed swap pages from the source to the consumer cache.
        // Also remove all source pages that are shadowed by consumer swap pages.
        _MergeSwapPages(source);

        // Move all not shadowed pages from the source to the consumer cache.
        if (source->page_count < page_count)
                _MergePagesSmallerSource(source);
        else
                _MergePagesSmallerConsumer(source);
}


void
VMAnonymousCache::DeleteObject()
{
        object_cache_delete(gAnonymousCacheObjectCache, this);
}


void
VMAnonymousCache::_SwapBlockBuild(off_t startPageIndex,
        swap_addr_t startSlotIndex, uint32 count)
{
        WriteLocker locker(sSwapHashLock);

        uint32 left = count;
        for (uint32 i = 0, j = 0; i < count; i += j) {
                off_t pageIndex = startPageIndex + i;
                swap_addr_t slotIndex = startSlotIndex + i;

                swap_hash_key key = { this, pageIndex };

                swap_block* swap = sSwapHashTable.Lookup(key);
                while (swap == NULL) {
                        swap = (swap_block*)object_cache_alloc(sSwapBlockCache,
                                CACHE_DONT_WAIT_FOR_MEMORY | CACHE_DONT_LOCK_KERNEL_SPACE);
                        if (swap == NULL) {
                                // Wait a short time until memory is available again.
                                locker.Unlock();
                                snooze(10000);
                                locker.Lock();
                                swap = sSwapHashTable.Lookup(key);
                                continue;
                        }

                        swap->key.cache = this;
                        swap->key.page_index = pageIndex & ~(off_t)SWAP_BLOCK_MASK;
                        swap->used = 0;
                        for (uint32 i = 0; i < SWAP_BLOCK_PAGES; i++)
                                swap->swap_slots[i] = SWAP_SLOT_NONE;

                        sSwapHashTable.InsertUnchecked(swap);
                }

                swap_addr_t blockIndex = pageIndex & SWAP_BLOCK_MASK;
                for (j = 0; blockIndex < SWAP_BLOCK_PAGES && left > 0; j++) {
                        swap->swap_slots[blockIndex++] = slotIndex + j;
                        left--;
                }

                swap->used += j;
        }
}


void
VMAnonymousCache::_SwapBlockFree(off_t startPageIndex, uint32 count)
{
        WriteLocker locker(sSwapHashLock);

        uint32 left = count;
        for (uint32 i = 0, j = 0; i < count; i += j) {
                off_t pageIndex = startPageIndex + i;
                swap_hash_key key = { this, pageIndex };
                swap_block* swap = sSwapHashTable.Lookup(key);

                ASSERT(swap != NULL);

                swap_addr_t blockIndex = pageIndex & SWAP_BLOCK_MASK;
                for (j = 0; blockIndex < SWAP_BLOCK_PAGES && left > 0; j++) {
                        swap->swap_slots[blockIndex++] = SWAP_SLOT_NONE;
                        left--;
                }

                swap->used -= j;
                if (swap->used == 0) {
                        sSwapHashTable.RemoveUnchecked(swap);
                        object_cache_free(sSwapBlockCache, swap,
                                CACHE_DONT_WAIT_FOR_MEMORY | CACHE_DONT_LOCK_KERNEL_SPACE);
                }
        }
}


swap_addr_t
VMAnonymousCache::_SwapBlockGetAddress(off_t pageIndex)
{
        ReadLocker locker(sSwapHashLock);

        swap_hash_key key = { this, pageIndex };
        swap_block* swap = sSwapHashTable.Lookup(key);
        swap_addr_t slotIndex = SWAP_SLOT_NONE;

        if (swap != NULL) {
                swap_addr_t blockIndex = pageIndex & SWAP_BLOCK_MASK;
                slotIndex = swap->swap_slots[blockIndex];
        }

        return slotIndex;
}


status_t
VMAnonymousCache::_Commit(off_t size, int priority)
{
        TRACE("%p->VMAnonymousCache::_Commit(%" B_PRIdOFF "), already committed: "
                "%" B_PRIdOFF " (%" B_PRIdOFF " swap)\n", this, size, committed_size,
                fCommittedSwapSize);

        // Basic strategy: reserve swap space first, only when running out of swap
        // space, reserve real memory.

        off_t committedMemory = committed_size - fCommittedSwapSize;

        // Regardless of whether we're asked to grow or shrink the commitment,
        // we always try to reserve as much as possible of the final commitment
        // in the swap space.
        if (size > fCommittedSwapSize) {
                fCommittedSwapSize += swap_space_reserve(size - fCommittedSwapSize);
                committed_size = fCommittedSwapSize + committedMemory;
                if (size > fCommittedSwapSize) {
                        TRACE("%p->VMAnonymousCache::_Commit(%" B_PRIdOFF "), reserved "
                                "only %" B_PRIdOFF " swap\n", this, size, fCommittedSwapSize);
                }
        }

        if (committed_size == size)
                return B_OK;

        if (committed_size > size) {
                // The commitment shrinks -- unreserve real memory first.
                off_t toUnreserve = committed_size - size;
                if (committedMemory > 0) {
                        off_t unreserved = min_c(toUnreserve, committedMemory);
                        vm_unreserve_memory(unreserved);
                        committedMemory -= unreserved;
                        committed_size -= unreserved;
                        toUnreserve -= unreserved;
                }

                // Unreserve swap space.
                if (toUnreserve > 0) {
                        swap_space_unreserve(toUnreserve);
                        fCommittedSwapSize -= toUnreserve;
                        committed_size -= toUnreserve;
                }

                return B_OK;
        }

        // The commitment grows -- we have already tried to reserve swap space at
        // the start of the method, so we try to reserve real memory, now.

        off_t toReserve = size - committed_size;
        if (vm_try_reserve_memory(toReserve, priority, 1000000) != B_OK) {
                dprintf("%p->VMAnonymousCache::_Commit(%" B_PRIdOFF "): Failed to "
                        "reserve %" B_PRIdOFF " bytes of RAM\n", this, size, toReserve);
                return B_NO_MEMORY;
        }

        committed_size = size;
        return B_OK;
}


void
VMAnonymousCache::_MergePagesSmallerSource(VMAnonymousCache* source)
{
        // The source cache has less pages than the consumer (this cache), so we
        // iterate through the source's pages and move the ones that are not
        // shadowed up to the consumer.

        for (VMCachePagesTree::Iterator it = source->pages.GetIterator();
                        vm_page* page = it.Next();) {
                // Note: Removing the current node while iterating through a
                // IteratableSplayTree is safe.
                vm_page* consumerPage = LookupPage(
                        (off_t)page->cache_offset << PAGE_SHIFT);
                if (consumerPage == NULL) {
                        // the page is not yet in the consumer cache - move it upwards
                        ASSERT_PRINT(!page->busy, "page: %p", page);
                        MovePage(page);
                }
        }
}


void
VMAnonymousCache::_MergePagesSmallerConsumer(VMAnonymousCache* source)
{
        // The consumer (this cache) has less pages than the source, so we move the
        // consumer's pages to the source (freeing shadowed ones) and finally just
        // all pages of the source back to the consumer.

        for (VMCachePagesTree::Iterator it = pages.GetIterator();
                vm_page* page = it.Next();) {
                // If a source page is in the way, remove and free it.
                vm_page* sourcePage = source->LookupPage(
                        (off_t)page->cache_offset << PAGE_SHIFT);
                if (sourcePage != NULL) {
                        DEBUG_PAGE_ACCESS_START(sourcePage);
                        ASSERT_PRINT(!sourcePage->busy, "page: %p", sourcePage);
                        ASSERT_PRINT(sourcePage->WiredCount() == 0
                                        && sourcePage->mappings.IsEmpty(),
                                "sourcePage: %p, page: %p", sourcePage, page);
                        source->RemovePage(sourcePage);
                        vm_page_free(source, sourcePage);
                }

                // Note: Removing the current node while iterating through a
                // IteratableSplayTree is safe.
                source->MovePage(page);
        }

        MoveAllPages(source);
}


void
VMAnonymousCache::_MergeSwapPages(VMAnonymousCache* source)
{
        // If neither source nor consumer have swap pages, we don't have to do
        // anything.
        if (source->fAllocatedSwapSize == 0 && fAllocatedSwapSize == 0)
                return;

        for (off_t offset = source->virtual_base
                & ~(off_t)(B_PAGE_SIZE * SWAP_BLOCK_PAGES - 1);
                offset < source->virtual_end;
                offset += B_PAGE_SIZE * SWAP_BLOCK_PAGES) {

                WriteLocker locker(sSwapHashLock);

                off_t swapBlockPageIndex = offset >> PAGE_SHIFT;
                swap_hash_key key = { source, swapBlockPageIndex };
                swap_block* sourceSwapBlock = sSwapHashTable.Lookup(key);

                // remove the source swap block -- we will either take over the swap
                // space (and the block) or free it
                if (sourceSwapBlock != NULL)
                        sSwapHashTable.RemoveUnchecked(sourceSwapBlock);

                key.cache = this;
                swap_block* swapBlock = sSwapHashTable.Lookup(key);

                locker.Unlock();

                // remove all source pages that are shadowed by consumer swap pages
                if (swapBlock != NULL) {
                        for (uint32 i = 0; i < SWAP_BLOCK_PAGES; i++) {
                                if (swapBlock->swap_slots[i] != SWAP_SLOT_NONE) {
                                        vm_page* page = source->LookupPage(
                                                (off_t)(swapBlockPageIndex + i) << PAGE_SHIFT);
                                        if (page != NULL) {
                                                DEBUG_PAGE_ACCESS_START(page);
                                                ASSERT_PRINT(!page->busy, "page: %p", page);
                                                source->RemovePage(page);
                                                vm_page_free(source, page);
                                        }
                                }
                        }
                }

                if (sourceSwapBlock == NULL)
                        continue;

                for (uint32 i = 0; i < SWAP_BLOCK_PAGES; i++) {
                        off_t pageIndex = swapBlockPageIndex + i;
                        swap_addr_t sourceSlotIndex = sourceSwapBlock->swap_slots[i];

                        if (sourceSlotIndex == SWAP_SLOT_NONE)
                                continue;

                        if ((swapBlock != NULL
                                        && swapBlock->swap_slots[i] != SWAP_SLOT_NONE)
                                || LookupPage((off_t)pageIndex << PAGE_SHIFT) != NULL) {
                                // The consumer already has a page or a swapped out page
                                // at this index. So we can free the source swap space.
                                swap_slot_dealloc(sourceSlotIndex, 1);
                                sourceSwapBlock->swap_slots[i] = SWAP_SLOT_NONE;
                                sourceSwapBlock->used--;
                        }

                        // We've either freed the source swap page or are going to move it
                        // to the consumer. At any rate, the source cache doesn't own it
                        // anymore.
                        source->fAllocatedSwapSize -= B_PAGE_SIZE;
                }

                // All source swap pages that have not been freed yet are taken over by
                // the consumer.
                fAllocatedSwapSize += B_PAGE_SIZE * (off_t)sourceSwapBlock->used;

                if (sourceSwapBlock->used == 0) {
                        // All swap pages have been freed -- we can discard the source swap
                        // block.
                        object_cache_free(sSwapBlockCache, sourceSwapBlock,
                                CACHE_DONT_WAIT_FOR_MEMORY | CACHE_DONT_LOCK_KERNEL_SPACE);
                } else if (swapBlock == NULL) {
                        // We need to take over some of the source's swap pages and there's
                        // no swap block in the consumer cache. Just take over the source
                        // swap block.
                        sourceSwapBlock->key.cache = this;
                        locker.Lock();
                        sSwapHashTable.InsertUnchecked(sourceSwapBlock);
                        locker.Unlock();
                } else {
                        // We need to take over some of the source's swap pages and there's
                        // already a swap block in the consumer cache. Copy the respective
                        // swap addresses and discard the source swap block.
                        for (uint32 i = 0; i < SWAP_BLOCK_PAGES; i++) {
                                if (sourceSwapBlock->swap_slots[i] != SWAP_SLOT_NONE)
                                        swapBlock->swap_slots[i] = sourceSwapBlock->swap_slots[i];
                        }

                        object_cache_free(sSwapBlockCache, sourceSwapBlock,
                                CACHE_DONT_WAIT_FOR_MEMORY | CACHE_DONT_LOCK_KERNEL_SPACE);
                }
        }
}


// #pragma mark -


// TODO: This can be removed if we get BFS uuid's
struct VolumeInfo {
        char name[B_FILE_NAME_LENGTH];
        char device[B_FILE_NAME_LENGTH];
        char filesystem[B_OS_NAME_LENGTH];
        off_t capacity;
};


class PartitionScorer : public KPartitionVisitor {
public:
        PartitionScorer(VolumeInfo& volumeInfo)
                :
                fBestPartition(NULL),
                fBestScore(-1),
                fVolumeInfo(volumeInfo)
        {
        }

        virtual bool VisitPre(KPartition* partition)
        {
                if (!partition->ContainsFileSystem())
                        return false;

                KPath path;
                partition->GetPath(&path);

                int score = 0;
                if (strcmp(fVolumeInfo.name, partition->ContentName()) == 0)
                        score += 4;
                if (strcmp(fVolumeInfo.device, path.Path()) == 0)
                        score += 3;
                if (fVolumeInfo.capacity == partition->Size())
                        score += 2;
                if (strcmp(fVolumeInfo.filesystem,
                        partition->DiskSystem()->ShortName()) == 0) {
                        score += 1;
                }
                if (score >= 4 && score > fBestScore) {
                        fBestPartition = partition;
                        fBestScore = score;
                }

                return false;
        }

        KPartition* fBestPartition;

private:
        int32           fBestScore;
        VolumeInfo      fVolumeInfo;
};


status_t
get_mount_point(KPartition* partition, KPath* mountPoint)
{
        if (!mountPoint || !partition->ContainsFileSystem())
                return B_BAD_VALUE;

        const char* volumeName = partition->ContentName();
        if (!volumeName || strlen(volumeName) == 0)
                volumeName = partition->Name();
        if (!volumeName || strlen(volumeName) == 0)
                volumeName = "unnamed volume";

        char basePath[B_PATH_NAME_LENGTH];
        int32 len = snprintf(basePath, sizeof(basePath), "/%s", volumeName);
        for (int32 i = 1; i < len; i++)
                if (basePath[i] == '/')
                basePath[i] = '-';
        char* path = mountPoint->LockBuffer();
        int32 pathLen = mountPoint->BufferSize();
        strncpy(path, basePath, pathLen);

        struct stat dummy;
        for (int i = 1; ; i++) {
                if (stat(path, &dummy) != 0)
                        break;
                snprintf(path, pathLen, "%s%d", basePath, i);
        }

        mountPoint->UnlockBuffer();
        return B_OK;
}


status_t
swap_file_add(const char* path)
{
        // open the file
        int fd = open(path, O_RDWR | O_NOCACHE, S_IRUSR | S_IWUSR);
        if (fd < 0)
                return errno;

        // fstat() it and check whether we can use it
        struct stat st;
        if (fstat(fd, &st) < 0) {
                close(fd);
                return errno;
        }

        if (!(S_ISREG(st.st_mode) || S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))) {
                close(fd);
                return B_BAD_VALUE;
        }

        if (st.st_size < B_PAGE_SIZE) {
                close(fd);
                return B_BAD_VALUE;
        }

        // get file descriptor, vnode, and cookie
        file_descriptor* descriptor = get_fd(get_current_io_context(true), fd);
        put_fd(descriptor);

        vnode* node = fd_vnode(descriptor);
        if (node == NULL) {
                close(fd);
                return B_BAD_VALUE;
        }

        // do the allocations and prepare the swap_file structure
        swap_file* swap = (swap_file*)malloc(sizeof(swap_file));
        if (swap == NULL) {
                close(fd);
                return B_NO_MEMORY;
        }

        swap->fd = fd;
        swap->vnode = node;
        swap->cookie = descriptor->cookie;

        uint32 pageCount = st.st_size >> PAGE_SHIFT;
        swap->bmp = radix_bitmap_create(pageCount);
        if (swap->bmp == NULL) {
                free(swap);
                close(fd);
                return B_NO_MEMORY;
        }

        // set slot index and add this file to swap file list
        mutex_lock(&sSwapFileListLock);
        // TODO: Also check whether the swap file is already registered!
        if (sSwapFileList.IsEmpty()) {
                swap->first_slot = 0;
                swap->last_slot = pageCount;
        } else {
                // leave one page gap between two swap files
                swap->first_slot = sSwapFileList.Last()->last_slot + 1;
                swap->last_slot = swap->first_slot + pageCount;
        }
        sSwapFileList.Add(swap);
        sSwapFileCount++;
        mutex_unlock(&sSwapFileListLock);

        mutex_lock(&sAvailSwapSpaceLock);
        sAvailSwapSpace += (off_t)pageCount * B_PAGE_SIZE;
        mutex_unlock(&sAvailSwapSpaceLock);

        return B_OK;
}


status_t
swap_file_delete(const char* path)
{
        vnode* node = NULL;
        status_t status = vfs_get_vnode_from_path(path, true, &node);
        if (status != B_OK)
                return status;

        MutexLocker locker(sSwapFileListLock);

        swap_file* swapFile = NULL;
        for (SwapFileList::Iterator it = sSwapFileList.GetIterator();
                        (swapFile = it.Next()) != NULL;) {
                if (swapFile->vnode == node)
                        break;
        }

        vfs_put_vnode(node);

        if (swapFile == NULL)
                return B_ERROR;

        // if this file is currently used, we can't delete
        // TODO: mark this swap file deleting, and remove it after releasing
        // all the swap space
        if (swapFile->bmp->free_slots < swapFile->last_slot - swapFile->first_slot)
                return B_ERROR;

        sSwapFileList.Remove(swapFile);
        sSwapFileCount--;
        locker.Unlock();

        mutex_lock(&sAvailSwapSpaceLock);
        sAvailSwapSpace -= (off_t)(swapFile->last_slot - swapFile->first_slot)
                * B_PAGE_SIZE;
        mutex_unlock(&sAvailSwapSpaceLock);

        close(swapFile->fd);
        radix_bitmap_destroy(swapFile->bmp);
        free(swapFile);

        return B_OK;
}


void
swap_init(void)
{
        // create swap block cache
        sSwapBlockCache = create_object_cache("swapblock", sizeof(swap_block),
                sizeof(void*), NULL, NULL, NULL);
        if (sSwapBlockCache == NULL)
                panic("swap_init(): can't create object cache for swap blocks\n");

        status_t error = object_cache_set_minimum_reserve(sSwapBlockCache,
                MIN_SWAP_BLOCK_RESERVE);
        if (error != B_OK) {
                panic("swap_init(): object_cache_set_minimum_reserve() failed: %s",
                        strerror(error));
        }

        // init swap hash table
        sSwapHashTable.Init(INITIAL_SWAP_HASH_SIZE);
        rw_lock_init(&sSwapHashLock, "swaphash");

        error = register_resource_resizer(swap_hash_resizer, NULL,
                SWAP_HASH_RESIZE_INTERVAL);
        if (error != B_OK) {
                panic("swap_init(): Failed to register swap hash resizer: %s",
                        strerror(error));
        }

        // init swap file list
        mutex_init(&sSwapFileListLock, "swaplist");
        sSwapFileAlloc = NULL;
        sSwapFileCount = 0;

        // init available swap space
        mutex_init(&sAvailSwapSpaceLock, "avail swap space");
        sAvailSwapSpace = 0;

        add_debugger_command_etc("swap", &dump_swap_info,
                "Print infos about the swap usage",
                "\n"
                "Print infos about the swap usage.\n", 0);
}


void
swap_init_post_modules()
{
        // Never try to create a swap file on a read-only device - when booting
        // from CD, the write overlay is used.
        if (gReadOnlyBootDevice)
                return;

        bool swapEnabled = true;
        bool swapAutomatic = true;
        off_t swapSize = 0;

        dev_t swapDeviceID = -1;
        VolumeInfo selectedVolume = {};

        void* settings = load_driver_settings("virtual_memory");

        if (settings != NULL) {
                // We pass a lot of information on the swap device, this is mostly to
                // ensure that we are dealing with the same device that was configured.

                // TODO: Some kind of BFS uuid would be great here :)
                const char* enabled = get_driver_parameter(settings, "vm", NULL, NULL);

                if (enabled != NULL) {
                        swapEnabled = get_driver_boolean_parameter(settings, "vm",
                                true, false);
                        swapAutomatic = get_driver_boolean_parameter(settings, "swap_auto",
                                true, false);

                        if (swapEnabled && !swapAutomatic) {
                                const char* size = get_driver_parameter(settings, "swap_size",
                                        NULL, NULL);
                                const char* volume = get_driver_parameter(settings,
                                        "swap_volume_name", NULL, NULL);
                                const char* device = get_driver_parameter(settings,
                                        "swap_volume_device", NULL, NULL);
                                const char* filesystem = get_driver_parameter(settings,
                                        "swap_volume_filesystem", NULL, NULL);
                                const char* capacity = get_driver_parameter(settings,
                                        "swap_volume_capacity", NULL, NULL);

                                if (size != NULL && device != NULL && volume != NULL
                                        && filesystem != NULL && capacity != NULL) {
                                        // User specified a size / volume that seems valid
                                        swapAutomatic = false;
                                        swapSize = atoll(size);
                                        strlcpy(selectedVolume.name, volume,
                                                sizeof(selectedVolume.name));
                                        strlcpy(selectedVolume.device, device,
                                                sizeof(selectedVolume.device));
                                        strlcpy(selectedVolume.filesystem, filesystem,
                                                sizeof(selectedVolume.filesystem));
                                        selectedVolume.capacity = atoll(capacity);
                                } else {
                                        // Something isn't right with swap config, go auto
                                        swapAutomatic = true;
                                        dprintf("%s: virtual_memory configuration is invalid, "
                                                "using automatic swap\n", __func__);
                                }
                        }
                }
                unload_driver_settings(settings);
        }

        if (swapAutomatic) {
                swapSize = (off_t)vm_page_num_pages() * B_PAGE_SIZE;
                if (swapSize <= (1024 * 1024 * 1024)) {
                        // Memory under 1GB? double the swap
                        swapSize *= 2;
                }
                // Automatic swap defaults to the boot device
                swapDeviceID = gBootDevice;
        }

        if (!swapEnabled || swapSize < B_PAGE_SIZE) {
                dprintf("%s: virtual_memory is disabled\n", __func__);
                return;
        }

        if (!swapAutomatic && swapDeviceID < 0) {
                // If user-specified swap, and no swap device has been chosen yet...
                KDiskDeviceManager::CreateDefault();
                KDiskDeviceManager* manager = KDiskDeviceManager::Default();
                PartitionScorer visitor(selectedVolume);

                KDiskDevice* device;
                int32 cookie = 0;
                while ((device = manager->NextDevice(&cookie)) != NULL) {
                        if (device->IsReadOnlyMedia() || device->IsWriteOnce()
                                || device->IsRemovable()) {
                                continue;
                        }
                        device->VisitEachDescendant(&visitor);
                }

                if (!visitor.fBestPartition) {
                        dprintf("%s: Can't find configured swap partition '%s'\n",
                                __func__, selectedVolume.name);
                } else {
                        if (visitor.fBestPartition->IsMounted())
                                swapDeviceID = visitor.fBestPartition->VolumeID();
                        else {
                                KPath devPath, mountPoint;
                                visitor.fBestPartition->GetPath(&devPath);
                                get_mount_point(visitor.fBestPartition, &mountPoint);
                                const char* mountPath = mountPoint.Path();
                                mkdir(mountPath, S_IRWXU | S_IRWXG | S_IRWXO);
                                swapDeviceID = _kern_mount(mountPath, devPath.Path(),
                                        NULL, 0, NULL, 0);
                                if (swapDeviceID < 0) {
                                        dprintf("%s: Can't mount configured swap partition '%s'\n",
                                                __func__, selectedVolume.name);
                                }
                        }
                }
        }

        if (swapDeviceID < 0)
                swapDeviceID = gBootDevice;

        // We now have a swapDeviceID which is used for the swap file

        KPath path;
        struct fs_info info;
        _kern_read_fs_info(swapDeviceID, &info);
        if (swapDeviceID == gBootDevice)
                path = kDefaultSwapPath;
        else {
                vfs_entry_ref_to_path(info.dev, info.root, ".", true, path.LockBuffer(),
                        path.BufferSize());
                path.UnlockBuffer();
                path.Append("swap");
        }

        const char* swapPath = path.Path();

        // Swap size limits prevent oversized swap files
        if (swapAutomatic) {
                off_t existingSwapSize = 0;
                struct stat existingSwapStat;
                if (stat(swapPath, &existingSwapStat) == 0)
                        existingSwapSize = existingSwapStat.st_size;

                off_t freeSpace = info.free_blocks * info.block_size + existingSwapSize;

                // Adjust automatic swap to a maximum of 25% of the free space
                if (swapSize > (freeSpace / 4))
                        swapSize = (freeSpace / 4);
        }

        // Create swap file
        int fd = open(swapPath, O_RDWR | O_CREAT | O_NOCACHE, S_IRUSR | S_IWUSR);
        if (fd < 0) {
                dprintf("%s: Can't open/create %s: %s\n", __func__,
                        swapPath, strerror(errno));
                return;
        }

        struct stat stat;
        stat.st_size = swapSize;
        status_t error = _kern_write_stat(fd, NULL, false, &stat,
                sizeof(struct stat), B_STAT_SIZE | B_STAT_SIZE_INSECURE);
        if (error != B_OK) {
                dprintf("%s: Failed to resize %s to %" B_PRIdOFF " bytes: %s\n",
                        __func__, swapPath, swapSize, strerror(error));
        }

        close(fd);

        error = swap_file_add(swapPath);
        if (error != B_OK) {
                dprintf("%s: Failed to add swap file %s: %s\n", __func__, swapPath,
                        strerror(error));
        }
}


//! Used by page daemon to free swap space.
bool
swap_free_page_swap_space(vm_page* page)
{
        VMAnonymousCache* cache = dynamic_cast<VMAnonymousCache*>(page->Cache());
        if (cache == NULL)
                return false;

        swap_addr_t slotIndex = cache->_SwapBlockGetAddress(page->cache_offset);
        if (slotIndex == SWAP_SLOT_NONE)
                return false;

        swap_slot_dealloc(slotIndex, 1);
        cache->fAllocatedSwapSize -= B_PAGE_SIZE;
        cache->_SwapBlockFree(page->cache_offset, 1);

        return true;
}


uint32
swap_available_pages()
{
        mutex_lock(&sAvailSwapSpaceLock);
        uint32 avail = sAvailSwapSpace >> PAGE_SHIFT;
        mutex_unlock(&sAvailSwapSpaceLock);

        return avail;
}


uint32
swap_total_swap_pages()
{
        mutex_lock(&sSwapFileListLock);

        uint32 totalSwapSlots = 0;
        for (SwapFileList::Iterator it = sSwapFileList.GetIterator();
                swap_file* swapFile = it.Next();) {
                totalSwapSlots += swapFile->last_slot - swapFile->first_slot;
        }

        mutex_unlock(&sSwapFileListLock);

        return totalSwapSlots;
}


#endif  // ENABLE_SWAP_SUPPORT


void
swap_get_info(system_info* info)
{
#if ENABLE_SWAP_SUPPORT
        info->max_swap_pages = swap_total_swap_pages();
        info->free_swap_pages = swap_available_pages();
#else
        info->max_swap_space = 0;
        info->free_swap_space = 0;
#endif
}