ref: 059b863fab96cf3ba65e74ad67221eec6cbcbe0c
dir: /sys/src/cmd/disk/qcowfs.c/
/* Adapted from OpenBSD's src/usr.sbin/vmd/vioqcow2.c */
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <thread.h>
#include <9p.h>
typedef struct Header Header;
typedef struct Disk Disk;
struct Header {
char magic[4];
u32int version;
u64int backingoff;
u32int backingsz;
u32int clustershift;
u64int disksz;
u32int cryptmethod;
u32int l1sz;
u64int l1off;
u64int refoff;
u32int refsz;
u32int snapcount;
u64int snapsz;
/* v3 additions */
u64int incompatfeatures;
u64int compatfeatures;
u64int autoclearfeatures;
u32int reforder; /* Bits = 1 << reforder */
u32int headersz;
};
#define QCOW2_COMPRESSED 0x4000000000000000ull
#define QCOW2_INPLACE 0x8000000000000000ull
char *MAGIC_QCOW = "QFI\xfb";
enum{
QCOW2_DIRTY = 1 << 0,
QCOW2_CORRUPT = 1 << 1,
ICFEATURE_DIRTY = 1 << 0,
ICFEATURE_CORRUPT = 1 << 1,
ACFEATURE_BITEXT = 1 << 0,
HDRSZ = 4 + 4 + 8 + 4 + 4 + 8 + 4 + 4 + 8 + 8 + 4 + 4 + 8 + 8 + 8 + 8 + 4 + 4,
};
struct Disk {
RWLock lock;
Disk *base;
Header h;
int fd;
u64int *l1;
s64int end;
s64int clustersz;
s64int disksz; /* In bytes */
u32int cryptmethod;
u32int l1sz;
s64int l1off;
s64int refoff;
s64int refsz;
u32int nsnap;
s64int snapoff;
/* v3 features */
u64int incompatfeatures;
u64int autoclearfeatures;
u32int refssz;
u32int headersz;
};
#define PUT2(p, u) (p)[0] = (u)>>8, (p)[1] = (u)
#define GET2(p) (u16int)(p)[1] | (u16int)(p)[0]<<8
#define PUT4(p, u) (p)[0] = (u)>>24, (p)[1] = (u)>>16, (p)[2] = (u)>>8, (p)[3] = (u)
#define GET4(p) (u32int)(p)[3] | (u32int)(p)[2]<<8 | (u32int)(p)[1]<<16 | (u32int)(p)[0]<<24
#define PUT8(p, u) (p)[0] = (u)>>56, (p)[1] = (u)>>48, (p)[2] = (u)>>40, (p)[3] = (u)>>32, \
(p)[4] = (u)>>24, (p)[5] = (u)>>16, (p)[6] = (u)>>8, (p)[7] = (u)
#define GET8(p) (u64int)(p)[7] | (u64int)(p)[6]<<8 | (u64int)(p)[5]<<16 | (u64int)(p)[4]<<24 | \
(u64int)(p)[3]<<32 | (u64int)(p)[2]<<40 | (u64int)(p)[1]<<48 | (u64int)(p)[0]<<56
int
ftruncate(int fd, s64int length)
{
Dir d;
if(length < 0)
return -1;
nulldir(&d);
d.length = length;
if(dirfwstat(fd, &d) < 0)
return -1;
return 0;
}
static void
writehdr(Header *src, int fd)
{
uchar store[HDRSZ];
uchar *buf = store;
memcpy(buf, src->magic, strlen(src->magic)); buf += 4;
PUT4(buf, src->version); buf += 4;
PUT8(buf, src->backingoff); buf += 8;
PUT4(buf, src->backingsz); buf += 4;
PUT4(buf, src->clustershift); buf += 4;
PUT8(buf, src->disksz); buf += 8;
PUT4(buf, src->cryptmethod); buf += 4;
PUT4(buf, src->l1sz); buf += 4;
PUT8(buf, src->l1off); buf += 8;
PUT8(buf, src->refoff); buf += 8;
PUT4(buf, src->refsz); buf += 4;
PUT4(buf, src->snapcount); buf += 4;
PUT8(buf, src->snapsz); buf += 8;
PUT8(buf, src->incompatfeatures); buf += 8;
PUT8(buf, src->compatfeatures); buf += 8;
PUT8(buf, src->autoclearfeatures); buf += 8;
PUT4(buf, src->reforder); buf += 4;
PUT4(buf, src->headersz);
if(write(fd, store, sizeof store) != sizeof store)
sysfatal("writehdr: %r");
}
static void
readhdr(Header *dst, int fd)
{
uchar store[HDRSZ];
uchar *buf = store;
if(readn(fd, store, sizeof store) != sizeof store)
sysfatal("short read on header: %r");
if(memcmp(MAGIC_QCOW, buf, strlen(MAGIC_QCOW)) != 0)
sysfatal("invalid magic");
buf += 4;
dst->version = GET4(buf);
if(dst->version != 2 && dst->version != 3)
sysfatal("unsupported version: %d", dst->version);
buf += 4;
dst->backingoff = GET8(buf); buf += 8;
dst->backingsz = GET4(buf); buf += 4;
dst->clustershift = GET4(buf); buf += 4;
dst->disksz = GET8(buf); buf += 8;
dst->cryptmethod = GET4(buf); buf += 4;
dst->l1sz = GET4(buf); buf += 4;
dst->l1off = GET8(buf); buf += 8;
dst->refoff = GET8(buf); buf += 8;
dst->refsz = GET4(buf); buf += 4;
dst->snapcount = GET4(buf); buf += 4;
dst->snapsz = GET8(buf); buf += 8;
dst->incompatfeatures = GET8(buf); buf += 8;
dst->compatfeatures = GET8(buf); buf += 8;
dst->autoclearfeatures = GET8(buf); buf += 8;
dst->reforder = GET4(buf); buf += 4;
dst->headersz = GET4(buf);
}
#define ALIGNSZ(sz, align) ((sz + align - 1) & ~(align - 1))
static void
qc2create(int fd, u64int disksz)
{
Header hdr;
s64int base_len;
u64int l1sz, refsz, initsz, clustersz;
u64int l1off, refoff, i, l1entrysz, refentrysz;
uchar v[8], v2[2];
clustersz = 1<<16;
l1off = ALIGNSZ(HDRSZ, clustersz);
l1entrysz = clustersz * clustersz / 8;
l1sz = (disksz + l1entrysz - 1) / l1entrysz;
refoff = ALIGNSZ(l1off + 8*l1sz, clustersz);
refentrysz = clustersz * clustersz * clustersz / 2;
refsz = (disksz + refentrysz - 1) / refentrysz;
initsz = ALIGNSZ(refoff + refsz*clustersz, clustersz);
base_len = 0;
memcpy(hdr.magic, MAGIC_QCOW, strlen(MAGIC_QCOW));
hdr.version = 3;
hdr.backingoff = 0;
hdr.backingsz = base_len;
hdr.clustershift = 16;
hdr.disksz = disksz;
hdr.cryptmethod = 0;
hdr.l1sz = l1sz;
hdr.l1off = l1off;
hdr.refoff = refoff;
hdr.refsz = refsz;
hdr.snapcount = 0;
hdr.snapsz = 0;
hdr.incompatfeatures = 0;
hdr.compatfeatures = 0;
hdr.autoclearfeatures = 0;
hdr.reforder = 4;
hdr.headersz = HDRSZ;
writehdr(&hdr, fd);
if(ftruncate(fd, (s64int)initsz + clustersz) == -1)
sysfatal("ftruncate: %r");
assert(initsz/clustersz < clustersz/2);
PUT8(v, initsz);
if(pwrite(fd, v, sizeof v, refoff) != sizeof v)
sysfatal("q2create: pwrite: %r");
for(i=0; i < initsz/clustersz + 1; i++){
PUT2(v2, 1);
if(pwrite(fd, v2, sizeof v2, initsz + 2*i) != sizeof v2)
sysfatal("q2create: pwrite: %r");
}
}
static void
qc2open(Disk *disk, int fd)
{
int i;
Dir *d;
uchar buf[8];
disk->fd = fd;
disk->base = nil;
disk->l1 = nil;
readhdr(&disk->h, disk->fd);
disk->clustersz = 1ull << disk->h.clustershift;
disk->disksz = disk->h.disksz;
disk->cryptmethod = disk->h.cryptmethod;
disk->l1sz = disk->h.l1sz;
disk->l1off = disk->h.l1off;
disk->refsz = disk->h.refsz;
disk->refoff = disk->h.refoff;
disk->nsnap = disk->h.snapcount;
disk->snapoff = disk->h.snapsz;
disk->incompatfeatures = disk->h.incompatfeatures;
disk->autoclearfeatures = disk->h.autoclearfeatures;
disk->refssz = disk->h.refsz;
disk->headersz = disk->h.headersz;
if(disk->h.reforder != 4)
sysfatal("unsupoprted refcount size %d", disk->h.reforder);
disk->l1 = mallocz(disk->l1sz * 8, 1);
pread(disk->fd, disk->l1, disk->l1sz * 8, disk->l1off);
for(i = 0; i < disk->l1sz; i++){
memcpy(buf, disk->l1 + i, sizeof buf);
disk->l1[i] = GET8(buf);
}
d = dirfstat(fd);
if(d == nil)
sysfatal("dirfstat: %r");
disk->end = d->length;
free(d);
}
static u64int
xlate(Disk *disk, s64int off, int *inplace)
{
s64int l2sz, l1off, l2tab, l2off, cluster, clusteroff;
uchar buf[8];
/*
* Clear out inplace flag -- xlate misses should not
* be flagged as updatable in place. We will still
* return 0 from them, but this leaves less surprises
* in the API.
*/
if (inplace)
*inplace = 0;
rlock(&disk->lock);
if (off < 0)
goto err;
l2sz = disk->clustersz / 8;
l1off = (off / disk->clustersz) / l2sz;
if (l1off >= disk->l1sz)
goto err;
l2tab = disk->l1[l1off];
l2tab &= ~QCOW2_INPLACE;
if (l2tab == 0) {
runlock(&disk->lock);
return 0;
}
l2off = (off / disk->clustersz) % l2sz;
pread(disk->fd, buf, sizeof(buf), l2tab + l2off * 8);
cluster = GET8(buf);
/*
* cluster may be 0, but all future operations don't affect
* the return value.
*/
if (inplace)
*inplace = !!(cluster & QCOW2_INPLACE);
if (cluster & QCOW2_COMPRESSED)
sysfatal("xlate: compressed clusters unsupported");
runlock(&disk->lock);
clusteroff = 0;
cluster &= ~QCOW2_INPLACE;
if (cluster)
clusteroff = off % disk->clustersz;
return cluster + clusteroff;
err:
runlock(&disk->lock);
return -1;
}
static void
inc_refs(Disk *disk, s64int off, int newcluster)
{
s64int l1off, l1idx, l2idx, l2cluster;
u64int nper;
u16int refs;
uchar buf[8], buf2[2];
off &= ~QCOW2_INPLACE;
nper = disk->clustersz / 2;
l1idx = (off / disk->clustersz) / nper;
l2idx = (off / disk->clustersz) % nper;
l1off = disk->refoff + 8 * l1idx;
if (pread(disk->fd, buf, sizeof(buf), l1off) != 8)
sysfatal("could not read refs");
l2cluster = GET8(buf);
if (l2cluster == 0) {
l2cluster = disk->end;
disk->end += disk->clustersz;
if (ftruncate(disk->fd, disk->end) < 0)
sysfatal("inc_refs: failed to allocate ref block");
PUT8(buf, l2cluster);
if (pwrite(disk->fd, buf, sizeof(buf), l1off) != 8)
sysfatal("inc_refs: failed to write ref block");
}
refs = 1;
if (!newcluster) {
if (pread(disk->fd, buf2, sizeof buf2,
l2cluster + 2 * l2idx) != 2)
sysfatal("could not read ref cluster");
refs = GET2(buf2) + 1;
}
PUT2(buf2, refs);
if (pwrite(disk->fd, buf2, sizeof buf2, l2cluster + 2 * l2idx) != 2)
sysfatal("inc_refs: could not write ref block");
}
static void
copy_cluster(Disk *disk, Disk *base, u64int dst, u64int src)
{
char *scratch;
scratch = malloc(disk->clustersz);
if(!scratch)
sysfatal("out of memory");
src &= ~(disk->clustersz - 1);
dst &= ~(disk->clustersz - 1);
if(pread(base->fd, scratch, disk->clustersz, src) == -1)
sysfatal("copy_cluster: could not read cluster");
if(pwrite(disk->fd, scratch, disk->clustersz, dst) == -1)
sysfatal("copy_cluster: could not write cluster");
free(scratch);
}
/*
* Allocates a new cluster on disk, creating a new L2 table
* if needed. The cluster starts off with a refs of one,
* and the writable bit set.
*
* Returns -1 on error, and the physical address within the
* cluster of the write offset if it exists.
*/
static s64int
mkcluster(Disk *disk, Disk *base, s64int off, s64int src_phys)
{
s64int l2sz, l1off, l2tab, l2off, cluster, clusteroff, orig;
uchar buf[8];
wlock(&disk->lock);
/* L1 entries always exist */
l2sz = disk->clustersz / 8;
l1off = off / (disk->clustersz * l2sz);
if (l1off >= disk->l1sz)
sysfatal("l1 offset outside disk");
disk->end = (disk->end + disk->clustersz - 1) & ~(disk->clustersz - 1);
l2tab = disk->l1[l1off];
l2off = (off / disk->clustersz) % l2sz;
/* We may need to create or clone an L2 entry to map the block */
if (l2tab == 0 || (l2tab & QCOW2_INPLACE) == 0) {
orig = l2tab & ~QCOW2_INPLACE;
l2tab = disk->end;
disk->end += disk->clustersz;
if (ftruncate(disk->fd, disk->end) == -1)
sysfatal("mkcluster: ftruncate failed");
/*
* If we translated, found a L2 entry, but it needed to
* be copied, copy it.
*/
if (orig != 0)
copy_cluster(disk, disk, l2tab, orig);
/* Update l1 -- we flush it later */
disk->l1[l1off] = l2tab | QCOW2_INPLACE;
inc_refs(disk, l2tab, 1);
}
l2tab &= ~QCOW2_INPLACE;
/* Grow the disk */
if (ftruncate(disk->fd, disk->end + disk->clustersz) < 0)
sysfatal("mkcluster: could not grow disk");
if (src_phys > 0)
copy_cluster(disk, base, disk->end, src_phys);
cluster = disk->end;
disk->end += disk->clustersz;
PUT8(buf, cluster | QCOW2_INPLACE);
if (pwrite(disk->fd, buf, sizeof(buf), l2tab + l2off * 8) != 8)
sysfatal("mkcluster: could not write cluster");
PUT8(buf, disk->l1[l1off]);
if (pwrite(disk->fd, buf, sizeof(buf), disk->l1off + 8 * l1off) != 8)
sysfatal("mkcluster: could not write l1");
inc_refs(disk, cluster, 1);
wunlock(&disk->lock);
clusteroff = off % disk->clustersz;
if (cluster + clusteroff < disk->clustersz)
sysfatal("write would clobber header");
return cluster + clusteroff;
}
static void
fsread(Req *r)
{
char *buf;
Disk *disk, *d;
s64int off, phys_off, end, cluster_off;
u64int len, sz, rem;
off = r->ifcall.offset;
buf = r->ofcall.data;
len = r->ifcall.count;
disk = d = r->fid->file->aux;
end = off + len;
if(end > d->disksz)
len -= end - d->disksz;
rem = len;
while(rem != 0){
phys_off = xlate(d, off, nil);
if(phys_off <= 0)
d = nil;
cluster_off = off % disk->clustersz;
sz = disk->clustersz - cluster_off;
if(sz > rem)
sz = rem;
if(!d)
memset(buf, 0, sz);
else
sz = pread(d->fd, buf, sz, phys_off);
off += sz;
buf += sz;
rem -= sz;
}
r->ofcall.count = len;
respond(r, nil);
}
static void
fswrite(Req *r)
{
char *buf;
Disk *d;
s64int off, phys_off, end, cluster_off;
u64int len, sz, rem;
int inplace;
off = r->ifcall.offset;
buf = r->ifcall.data;
len = r->ifcall.count;
d = r->fid->file->aux;
inplace = 1;
end = off + len;
if(end > d->disksz){
respond(r, "end of device");
return;
}
rem = len;
while(off != end){
cluster_off = off % d->clustersz;
sz = d->clustersz - cluster_off;
if(sz > rem)
sz = rem;
phys_off = xlate(d, off, nil);
if(phys_off == -1){
respond(r, "xlate error");
return;
}
if(!inplace || phys_off == 0)
phys_off = mkcluster(d, d, off, phys_off);
if(phys_off == -1){
respond(r, "mkcluster error");
return;
}
if(phys_off < d->clustersz)
sysfatal("fswrite: writing reserved cluster");
if(pwrite(d->fd, buf, sz, phys_off) != sz){
respond(r, "phase error");
return;
}
off += sz;
buf += sz;
rem -= sz;
}
r->ofcall.count = len;
respond(r, nil);
}
Srv fs = {
.read = fsread,
.write = fswrite,
};
static void
usage(void)
{
fprint(2, "usage: %s [-s srv] [-m mntpt ] [-n size] file\n", argv0);
exits("usage");
}
void
main(int argc, char **argv)
{
int fd;
char *uid;
File *f;
Disk *d;
uvlong size;
int nflag;
char *mntpt = "/mnt/qcow";
char *srvname = nil;
size = 0;
nflag = 0;
ARGBEGIN{
case 'm':
mntpt = EARGF(usage());
break;
case 'n':
size = strtoull(EARGF(usage()), nil, 0);
nflag++;
break;
case 's':
srvname = EARGF(usage());
break;
default:
usage();
break;
}ARGEND
if(argc < 1)
usage();
if(nflag){
if((fd = create(argv[0], ORDWR, 0666)) < 0)
sysfatal("create: %r");
qc2create(fd, size);
seek(fd, 0, 0);
} else if((fd = open(argv[0], ORDWR)) < 0)
sysfatal("open: %r");
uid = getuser();
fs.tree = alloctree(uid, uid, 0755, nil);
if(fs.tree == nil)
sysfatal("alloctree: %r");
f = createfile(fs.tree->root, "data", uid, 0666, nil);
d = mallocz(sizeof(Disk), 1);
qc2open(d, fd);
f->aux = d;
f->length = d->disksz;
postmountsrv(&fs, srvname, mntpt, MREPL);
exits(nil);
}