minix/servers/vm/alloc.c
Ben Gras 565f13088f make vfs & filesystems use failable copying
Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.

Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.

This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.

Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.

	. kernel: add CPF_TRY flag to safecopies
	. kernel: only request writable ranges to VM for the
	  target buffer when copying fails
	. do copying in VFS TRY-first
	. some fixes in VM to build SANITYCHECK mode
	. add regression test for the cases where
	  - a FS system call needs memory mapped in a process that the
	    FS itself must map.
	  - such a range covers more than one file-mapped region.
	. add 'try' mode to vircopy, physcopy
	. add flags field to copy kernel call messages
	. if CP_FLAG_TRY is set, do not transparently try
	  to fix memory ranges
	. for use by VFS when accessing user buffers to avoid
	  deadlock
	. remove some obsolete backwards compatability assignments
        . VFS: let thread scheduling work for VM requests too
          Allows VFS to make calls to VM while suspending and resuming
          the currently running thread. Does currently not work for the
          main thread.
        . VM: add fix memory range call for use by VFS

Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-07-28 17:05:14 +02:00

548 lines
13 KiB
C

/* This file is concerned with allocating and freeing arbitrary-size blocks of
* physical memory.
*/
#define _SYSTEM 1
#include <minix/com.h>
#include <minix/callnr.h>
#include <minix/type.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/sysutil.h>
#include <minix/syslib.h>
#include <minix/debug.h>
#include <minix/bitmap.h>
#include <sys/mman.h>
#include <limits.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <memory.h>
#include "vm.h"
#include "proto.h"
#include "util.h"
#include "glo.h"
#include "sanitycheck.h"
#include "memlist.h"
/* Number of physical pages in a 32-bit address space */
#define NUMBER_PHYSICAL_PAGES (int)(0x100000000ULL/VM_PAGE_SIZE)
#define PAGE_BITMAP_CHUNKS BITMAP_CHUNKS(NUMBER_PHYSICAL_PAGES)
static bitchunk_t free_pages_bitmap[PAGE_BITMAP_CHUNKS];
#define PAGE_CACHE_MAX 10000
static int free_page_cache[PAGE_CACHE_MAX];
static int free_page_cache_size = 0;
/* Used for sanity check. */
static phys_bytes mem_low, mem_high;
static void free_pages(phys_bytes addr, int pages);
static phys_bytes alloc_pages(int pages, int flags);
#if SANITYCHECKS
struct {
int used;
const char *file;
int line;
} pagemap[NUMBER_PHYSICAL_PAGES];
#endif
#define page_isfree(i) GET_BIT(free_pages_bitmap, i)
#define RESERVEDMAGIC 0x6e4c74d5
#define MAXRESERVEDPAGES 300
#define MAXRESERVEDQUEUES 15
static struct reserved_pages {
struct reserved_pages *next; /* next in use */
int max_available; /* queue depth use, 0 if not in use at all */
int npages; /* number of consecutive pages */
int mappedin; /* must reserved pages also be mapped? */
int n_available; /* number of queue entries */
int allocflags; /* allocflags for alloc_mem */
struct reserved_pageslot {
phys_bytes phys;
void *vir;
} slots[MAXRESERVEDPAGES];
u32_t magic;
} reservedqueues[MAXRESERVEDQUEUES], *first_reserved_inuse = NULL;
int missing_spares = 0;
static void sanitycheck_queues(void)
{
struct reserved_pages *mrq;
int m = 0;
for(mrq = first_reserved_inuse; mrq; mrq = mrq->next) {
assert(mrq->max_available > 0);
assert(mrq->max_available >= mrq->n_available);
m += mrq->max_available - mrq->n_available;
}
assert(m == missing_spares);
}
static void sanitycheck_rq(struct reserved_pages *rq)
{
assert(rq->magic == RESERVEDMAGIC);
assert(rq->n_available >= 0);
assert(rq->n_available <= MAXRESERVEDPAGES);
assert(rq->n_available <= rq->max_available);
sanitycheck_queues();
}
void *reservedqueue_new(int max_available, int npages, int mapped, int allocflags)
{
int r;
struct reserved_pages *rq;
assert(max_available > 0);
assert(max_available < MAXRESERVEDPAGES);
assert(npages > 0);
assert(npages < 10);
for(r = 0; r < MAXRESERVEDQUEUES; r++)
if(!reservedqueues[r].max_available)
break;
if(r >= MAXRESERVEDQUEUES) {
printf("VM: %d reserved queues in use\n", MAXRESERVEDQUEUES);
return NULL;
}
rq = &reservedqueues[r];
memset(rq, 0, sizeof(*rq));
rq->next = first_reserved_inuse;
first_reserved_inuse = rq;
rq->max_available = max_available;
rq->npages = npages;
rq->mappedin = mapped;
rq->allocflags = allocflags;
rq->magic = RESERVEDMAGIC;
missing_spares += max_available;
return rq;
}
static void
reservedqueue_fillslot(struct reserved_pages *rq,
struct reserved_pageslot *rps, phys_bytes ph, void *vir)
{
rps->phys = ph;
rps->vir = vir;
assert(missing_spares > 0);
if(rq->mappedin) assert(vir);
missing_spares--;
rq->n_available++;
}
static int
reservedqueue_addslot(struct reserved_pages *rq)
{
phys_bytes cl, cl_addr;
void *vir;
struct reserved_pageslot *rps;
sanitycheck_rq(rq);
if((cl = alloc_mem(rq->npages, rq->allocflags)) == NO_MEM)
return ENOMEM;
cl_addr = CLICK2ABS(cl);
vir = NULL;
if(rq->mappedin) {
if(!(vir = vm_mappages(cl_addr, rq->npages))) {
free_mem(cl, rq->npages);
printf("reservedqueue_addslot: vm_mappages failed\n");
return ENOMEM;
}
}
rps = &rq->slots[rq->n_available];
reservedqueue_fillslot(rq, rps, cl_addr, vir);
return OK;
}
void reservedqueue_add(void *rq_v, void *vir, phys_bytes ph)
{
struct reserved_pages *rq = rq_v;
struct reserved_pageslot *rps;
sanitycheck_rq(rq);
rps = &rq->slots[rq->n_available];
reservedqueue_fillslot(rq, rps, ph, vir);
}
static int reservedqueue_fill(void *rq_v)
{
struct reserved_pages *rq = rq_v;
int r;
sanitycheck_rq(rq);
while(rq->n_available < rq->max_available)
if((r=reservedqueue_addslot(rq)) != OK)
return r;
return OK;
}
int
reservedqueue_alloc(void *rq_v, phys_bytes *ph, void **vir)
{
struct reserved_pages *rq = rq_v;
struct reserved_pageslot *rps;
sanitycheck_rq(rq);
if(rq->n_available < 1) return ENOMEM;
rq->n_available--;
missing_spares++;
rps = &rq->slots[rq->n_available];
*ph = rps->phys;
*vir = rps->vir;
sanitycheck_rq(rq);
return OK;
}
void alloc_cycle(void)
{
struct reserved_pages *rq;
sanitycheck_queues();
for(rq = first_reserved_inuse; rq && missing_spares > 0; rq = rq->next) {
sanitycheck_rq(rq);
reservedqueue_fill(rq);
sanitycheck_rq(rq);
}
sanitycheck_queues();
}
/*===========================================================================*
* alloc_mem *
*===========================================================================*/
phys_clicks alloc_mem(phys_clicks clicks, u32_t memflags)
{
/* Allocate a block of memory from the free list using first fit. The block
* consists of a sequence of contiguous bytes, whose length in clicks is
* given by 'clicks'. A pointer to the block is returned. The block is
* always on a click boundary. This procedure is called when memory is
* needed for FORK or EXEC.
*/
phys_clicks mem = NO_MEM, align_clicks = 0;
if(memflags & PAF_ALIGN64K) {
align_clicks = (64 * 1024) / CLICK_SIZE;
clicks += align_clicks;
} else if(memflags & PAF_ALIGN16K) {
align_clicks = (16 * 1024) / CLICK_SIZE;
clicks += align_clicks;
}
do {
mem = alloc_pages(clicks, memflags);
} while(mem == NO_MEM && cache_freepages(clicks) > 0);
if(mem == NO_MEM)
return mem;
if(align_clicks) {
phys_clicks o;
o = mem % align_clicks;
if(o > 0) {
phys_clicks e;
e = align_clicks - o;
free_mem(mem, e);
mem += e;
}
}
return mem;
}
void mem_add_total_pages(int pages)
{
total_pages += pages;
}
/*===========================================================================*
* free_mem *
*===========================================================================*/
void free_mem(phys_clicks base, phys_clicks clicks)
{
/* Return a block of free memory to the hole list. The parameters tell where
* the block starts in physical memory and how big it is. The block is added
* to the hole list. If it is contiguous with an existing hole on either end,
* it is merged with the hole or holes.
*/
if (clicks == 0) return;
assert(CLICK_SIZE == VM_PAGE_SIZE);
free_pages(base, clicks);
return;
}
/*===========================================================================*
* mem_init *
*===========================================================================*/
void mem_init(struct memory *chunks)
{
/* Initialize hole lists. There are two lists: 'hole_head' points to a linked
* list of all the holes (unused memory) in the system; 'free_slots' points to
* a linked list of table entries that are not in use. Initially, the former
* list has one entry for each chunk of physical memory, and the second
* list links together the remaining table slots. As memory becomes more
* fragmented in the course of time (i.e., the initial big holes break up into
* smaller holes), new table slots are needed to represent them. These slots
* are taken from the list headed by 'free_slots'.
*/
int i, first = 0;
total_pages = 0;
memset(free_pages_bitmap, 0, sizeof(free_pages_bitmap));
/* Use the chunks of physical memory to allocate holes. */
for (i=NR_MEMS-1; i>=0; i--) {
if (chunks[i].size > 0) {
phys_bytes from = CLICK2ABS(chunks[i].base),
to = CLICK2ABS(chunks[i].base+chunks[i].size)-1;
if(first || from < mem_low) mem_low = from;
if(first || to > mem_high) mem_high = to;
free_mem(chunks[i].base, chunks[i].size);
total_pages += chunks[i].size;
first = 0;
}
}
}
#if SANITYCHECKS
void mem_sanitycheck(const char *file, int line)
{
int i;
for(i = 0; i < NUMBER_PHYSICAL_PAGES; i++) {
if(!page_isfree(i)) continue;
MYASSERT(usedpages_add(i * VM_PAGE_SIZE, VM_PAGE_SIZE) == OK);
}
}
#endif
void memstats(int *nodes, int *pages, int *largest)
{
int i;
*nodes = 0;
*pages = 0;
*largest = 0;
for(i = 0; i < NUMBER_PHYSICAL_PAGES; i++) {
int size = 0;
while(i < NUMBER_PHYSICAL_PAGES && page_isfree(i)) {
size++;
i++;
}
if(size == 0) continue;
(*nodes)++;
(*pages)+= size;
if(size > *largest)
*largest = size;
}
}
static int findbit(int low, int startscan, int pages, int memflags, int *len)
{
int run_length = 0, i;
int freerange_start = startscan;
for(i = startscan; i >= low; i--) {
if(!page_isfree(i)) {
int pi;
int chunk = i/BITCHUNK_BITS, moved = 0;
run_length = 0;
pi = i;
while(chunk > 0 &&
!MAP_CHUNK(free_pages_bitmap, chunk*BITCHUNK_BITS)) {
chunk--;
moved = 1;
}
if(moved) { i = chunk * BITCHUNK_BITS + BITCHUNK_BITS; }
continue;
}
if(!run_length) { freerange_start = i; run_length = 1; }
else { freerange_start--; run_length++; }
assert(run_length <= pages);
if(run_length == pages) {
/* good block found! */
*len = run_length;
return freerange_start;
}
}
return NO_MEM;
}
/*===========================================================================*
* alloc_pages *
*===========================================================================*/
static phys_bytes alloc_pages(int pages, int memflags)
{
phys_bytes boundary16 = 16 * 1024 * 1024 / VM_PAGE_SIZE;
phys_bytes boundary1 = 1 * 1024 * 1024 / VM_PAGE_SIZE;
phys_bytes mem = NO_MEM, i; /* page number */
int maxpage = NUMBER_PHYSICAL_PAGES - 1;
static int lastscan = -1;
int startscan, run_length;
if(memflags & PAF_LOWER16MB)
maxpage = boundary16 - 1;
else if(memflags & PAF_LOWER1MB)
maxpage = boundary1 - 1;
else {
/* no position restrictions: check page cache */
if(pages == 1) {
while(free_page_cache_size > 0) {
i = free_page_cache[free_page_cache_size-1];
if(page_isfree(i)) {
free_page_cache_size--;
mem = i;
assert(mem != NO_MEM);
run_length = 1;
break;
}
free_page_cache_size--;
}
}
}
if(lastscan < maxpage && lastscan >= 0)
startscan = lastscan;
else startscan = maxpage;
if(mem == NO_MEM)
mem = findbit(0, startscan, pages, memflags, &run_length);
if(mem == NO_MEM)
mem = findbit(0, maxpage, pages, memflags, &run_length);
if(mem == NO_MEM)
return NO_MEM;
/* remember for next time */
lastscan = mem;
for(i = mem; i < mem + pages; i++) {
UNSET_BIT(free_pages_bitmap, i);
}
if(memflags & PAF_CLEAR) {
int s;
if ((s= sys_memset(NONE, 0, CLICK_SIZE*mem,
VM_PAGE_SIZE*pages)) != OK)
panic("alloc_mem: sys_memset failed: %d", s);
}
return mem;
}
/*===========================================================================*
* free_pages *
*===========================================================================*/
static void free_pages(phys_bytes pageno, int npages)
{
int i, lim = pageno + npages - 1;
#if JUNKFREE
if(sys_memset(NONE, 0xa5a5a5a5, VM_PAGE_SIZE * pageno,
VM_PAGE_SIZE * npages) != OK)
panic("free_pages: sys_memset failed");
#endif
for(i = pageno; i <= lim; i++) {
SET_BIT(free_pages_bitmap, i);
if(free_page_cache_size < PAGE_CACHE_MAX) {
free_page_cache[free_page_cache_size++] = i;
}
}
}
/*===========================================================================*
* printmemstats *
*===========================================================================*/
void printmemstats(void)
{
int nodes, pages, largest;
memstats(&nodes, &pages, &largest);
printf("%d blocks, %d pages (%lukB) free, largest %d pages (%lukB)\n",
nodes, pages, (unsigned long) pages * (VM_PAGE_SIZE/1024),
largest, (unsigned long) largest * (VM_PAGE_SIZE/1024));
}
#if SANITYCHECKS
/*===========================================================================*
* usedpages_reset *
*===========================================================================*/
void usedpages_reset(void)
{
memset(pagemap, 0, sizeof(pagemap));
}
/*===========================================================================*
* usedpages_add *
*===========================================================================*/
int usedpages_add_f(phys_bytes addr, phys_bytes len, const char *file, int line)
{
u32_t pagestart, pages;
if(!incheck)
return OK;
assert(!(addr % VM_PAGE_SIZE));
assert(!(len % VM_PAGE_SIZE));
assert(len > 0);
pagestart = addr / VM_PAGE_SIZE;
pages = len / VM_PAGE_SIZE;
while(pages > 0) {
phys_bytes thisaddr;
assert(pagestart > 0);
assert(pagestart < NUMBER_PHYSICAL_PAGES);
thisaddr = pagestart * VM_PAGE_SIZE;
assert(pagestart < NUMBER_PHYSICAL_PAGES);
if(pagemap[pagestart].used) {
static int warnings = 0;
if(warnings++ < 100)
printf("%s:%d: usedpages_add: addr 0x%lx reused, first %s:%d\n",
file, line, thisaddr, pagemap[pagestart].file, pagemap[pagestart].line);
util_stacktrace();
return EFAULT;
}
pagemap[pagestart].used = 1;
pagemap[pagestart].file = file;
pagemap[pagestart].line = line;
pages--;
pagestart++;
}
return OK;
}
#endif