ref: 4eddb6b732fee3caede4199645aafc5d31fb48b0
dir: /blk.c/
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <avl.h>
#include "dat.h"
#include "fns.h"
#include "atomic.h"
static vlong blkalloc_lk(Arena*, int);
static vlong blkalloc(int, uint);
static void blkdealloc_lk(Arena*, vlong);
static Blk* initblk(Blk*, vlong, vlong, int);
int
checkflag(Blk *b, int f)
{
long v;
v = agetl(&b->flag);
return (v & f) == f;
}
void
setflag(Blk *b, int f)
{
long ov, nv;
while(1){
ov = agetl(&b->flag);
nv = ov | f;
if(acasl(&b->flag, ov, nv))
break;
}
}
void
clrflag(Blk *b, int f)
{
long ov, nv;
while(1){
ov = agetl(&b->flag);
nv = ov & ~f;
if(acasl(&b->flag, ov, nv))
break;
}
}
void
syncblk(Blk *b)
{
assert(checkflag(b, Bfinal));
assert(b->bp.addr >= 0);
clrflag(b, Bdirty);
if(pwrite(fs->fd, b->buf, Blksz, b->bp.addr) == -1)
broke("%B %s: %r", b->bp, Eio);
}
static Blk*
readblk(vlong bp, int flg)
{
vlong off, rem, n;
char *p;
Blk *b;
assert(bp != -1);
b = cachepluck();
b->alloced = getcallerpc(&bp);
off = bp;
rem = Blksz;
while(rem != 0){
n = pread(fs->fd, b->buf, rem, off);
if(n <= 0)
error("%s: %r", Eio);
off += n;
rem -= n;
}
b->cnext = nil;
b->cprev = nil;
b->hnext = nil;
b->flag = 0;
b->bp.addr = bp;
b->bp.hash = -1;
b->bp.gen = -1;
b->fnext = nil;
b->nval = 0;
b->valsz = 0;
b->nbuf = 0;
b->bufsz = 0;
b->logsz = 0;
p = b->buf + 2;
b->type = (flg&GBraw) ? Tdat : UNPACK16(b->buf+0);
switch(b->type){
default:
broke("invalid block type %d @%llx", b->type, bp);
break;
case Tdat:
case Tsuper:
b->data = b->buf;
break;
case Tarena:
b->data = p;
break;
case Tdlist:
case Tlog:
b->logsz = UNPACK16(p); p += 2;
b->logh = UNPACK64(p); p += 8;
b->logp = unpackbp(p, Ptrsz); p += Ptrsz;
assert(p - b->buf == Loghdsz);
b->data = p;
break;
case Tpivot:
b->nval = UNPACK16(p); p += 2;
b->valsz = UNPACK16(p); p += 2;
b->nbuf = UNPACK16(p); p += 2;
b->bufsz = UNPACK16(p); p += 2;
assert(p - b->buf == Pivhdsz);
b->data = p;
break;
case Tleaf:
b->nval = UNPACK16(p); p += 2;
b->valsz = UNPACK16(p); p += 2;
assert(p - b->buf == Leafhdsz);
b->data = p;
break;
}
assert(b->magic == Magic);
return b;
}
static Arena*
pickarena(uint ty, uint hint, int tries)
{
uint n;
n = hint + tries + ainc(&fs->roundrobin)/1024;
if(ty == Tdat)
n++;
if(hint % fs->narena == 0)
n++;
return &fs->arenas[n%fs->narena];
}
Arena*
getarena(vlong b)
{
int hi, lo, mid;
vlong alo, ahi;
Arena *a;
lo = 0;
hi = fs->narena;
if(b == 0)
return &fs->arenas[0];
while(1){
mid = (hi + lo)/2;
a = &fs->arenas[mid];
alo = a->h0->bp.addr;
ahi = alo + a->size + 2*Blksz;
//print("getarena %d [%d] %d (%#llx %#llx) %llx\n", lo, mid, hi, alo, ahi, b);
if(b < alo)
hi = mid-1;
else if(b > ahi)
lo = mid+1;
else
return a;
}
}
static void
freerange(Avltree *t, vlong off, vlong len)
{
Arange *r, *s;
assert(len % Blksz == 0);
if((r = calloc(1, sizeof(Arange))) == nil)
error(Enomem);
r->off = off;
r->len = len;
assert(avllookup(t, r, 0) == nil);
avlinsert(t, r);
Again:
s = (Arange*)avlprev(r);
if(s != nil && s->off+s->len == r->off){
avldelete(t, r);
s->len = s->len + r->len;
free(r);
r = s;
goto Again;
}
s = (Arange*)avlnext(r);
if(s != nil && r->off+r->len == s->off){
avldelete(t, r);
s->off = r->off;
s->len = s->len + r->len;
free(r);
r = s;
goto Again;
}
}
static void
grabrange(Avltree *t, vlong off, vlong len)
{
Arange *r, *s, q;
vlong l;
assert(len % Blksz == 0);
q.off = off;
q.len = len;
r = (Arange*)avllookup(t, &q.Avl, -1);
if(r == nil || off + len > r->off + r->len)
abort();
if(off == r->off){
r->off += len;
r->len -= len;
}else if(off + len == r->off + r->len){
r->len -= len;
}else if(off > r->off && off+len < r->off + r->len){
s = emalloc(sizeof(Arange), 0);
l = r->len;
s->off = off + len;
r->len = off - r->off;
s->len = l - r->len - len;
avlinsert(t, s);
}else
abort();
if(r->len == 0){
avldelete(t, r);
free(r);
}
}
static Blk*
mklogblk(Arena *a, vlong o)
{
Blk *lb;
lb = a->logbuf[a->lbidx++ % nelem(a->logbuf)];
if(lb->bp.addr != -1)
cachedel(lb->bp.addr);
initblk(lb, o, -1, Tlog);
finalize(lb);
syncblk(lb);
return lb;
}
/*
* Logs an allocation. Must be called
* with arena lock held. Duplicates some
* of the work in allocblk to prevent
* recursion.
*/
static void
logappend(Arena *a, vlong off, vlong len, int op)
{
vlong o, start, end;
Blk *nl, *lb;
char *p, *name;
lb = a->logtl;
assert((off & 0xff) == 0);
assert(op == LogAlloc || op == LogFree || op == LogSync);
if(op != LogSync){
start = a->h0->bp.addr;
end = start + a->size + 2*Blksz;
assert(lb == nil || lb->type == Tlog);
assert(off >= start);
assert(off <= end);
}
switch(op){
case LogAlloc: name = "alloc"; break;
case LogFree: name = "free"; break;
case LogSync: name = "sync"; break;
default: name = "???"; break;
}
assert(lb == nil || lb->logsz >= 0);
dprint("logop %llx+%llx@%x: %s\n", off, len, lb?lb->logsz:-1, name);
/*
* move to the next block when we have
* too little room in the log:
* We're appending up to 16 bytes as
* part of the operation, followed by
* 16 bytes of new log entry allocation
* and chaining.
*/
if(lb == nil || lb->logsz >= Logspc - Logslop){
if((o = blkalloc_lk(a, 1)) == -1)
error(Efs);
nl = mklogblk(a, o);
p = lb->data + lb->logsz;
PACK64(p, o|LogAlloc1);
lb->logsz += 8;
lb->logp = nl->bp;
setflag(lb, Bdirty);
finalize(lb);
syncblk(lb);
a->logtl = nl;
a->nlog++;
lb = nl;
}
setflag(lb, Bdirty);
if(len == Blksz){
if(op == LogAlloc)
op = LogAlloc1;
else if(op == LogFree)
op = LogFree1;
}
off |= op;
p = lb->data + lb->logsz;
PACK64(p, off);
lb->logsz += 8;
if(op >= Log2wide){
PACK64(p+8, len);
lb->logsz += 8;
}
}
void
loadlog(Arena *a, Bptr bp)
{
vlong ent, off, len, gen;
int op, i, n;
char *d;
Blk *b;
dprint("loadlog %B\n", bp);
while(1){
b = getblk(bp, 0);
dprint("\tload %B chain %B\n", bp, b->logp);
/* the hash covers the log and offset */
for(i = 0; i < b->logsz; i += n){
d = b->data + i;
ent = UNPACK64(d);
op = ent & 0xff;
off = ent & ~0xff;
n = (op >= Log2wide) ? 16 : 8;
switch(op){
case LogSync:
gen = ent >> 8;
dprint("\tlog@%d: sync %llx\n", i, gen);
if(gen >= fs->qgen){
if(a->logtl == nil){
b->logsz = i;
a->logtl = holdblk(b);
return;
}
dropblk(b);
return;
}
break;
case LogAlloc:
case LogAlloc1:
len = (op >= Log2wide) ? UNPACK64(d+8) : Blksz;
dprint("\tlog@%d alloc: %llx+%llx\n", i, off, len);
grabrange(a->free, off & ~0xff, len);
a->used += len;
break;
case LogFree:
case LogFree1:
len = (op >= Log2wide) ? UNPACK64(d+8) : Blksz;
dprint("\tlog@%d free: %llx+%llx\n", i, off, len);
freerange(a->free, off & ~0xff, len);
a->used -= len;
break;
default:
n = 0;
dprint("\tlog@%d: log op %d\n", i, op);
abort();
break;
}
}
if(b->logp.addr == -1){
a->logtl = b;
return;
}
bp = b->logp;
dropblk(b);
}
}
int
compresslog(Arena *a)
{
int i, nr, nblks;
vlong sz, *blks;
Blk *b, *nb;
Arange *r;
Bptr hd;
char *p;
if(a->logtl != nil && checkflag(a->logtl, Bdirty))
syncblk(a->logtl);
/*
* Prepare what we're writing back.
* Arenas must be sized so that we can
* keep the merged log in memory for
* a rewrite.
*/
sz = 0;
nr = 0;
a->nlog = 0;
for(r = (Arange*)avlmin(a->free); r != nil; r = (Arange*)avlnext(r)){
sz += 16;
nr++;
}
/*
* Make a pessimistic estimate of the number of blocks
* needed to store the ranges, as well as the blocks
* used to store the range allocations.
*
* This does modify the tree, but it's safe because
* we can only be removing entries from the tree, not
* splitting or inserting new ones.
*/
nblks = (sz+Logspc)/(Logspc - Logslop) + 16*nr/(Logspc-Logslop) + 1;
if((blks = calloc(nblks, sizeof(vlong))) == nil)
return -1;
if(waserror()){
free(blks);
return -1;
}
for(i = 0; i < nblks; i++)
if((blks[i] = blkalloc_lk(a, 1)) == -1)
error(Efs);
/* fill up the log with the ranges from the tree */
i = 0;
hd = (Bptr){blks[0], -1, -1};
b = cachepluck();
initblk(b, blks[i++], -1, Tlog);
for(r = (Arange*)avlmin(a->free); r != nil; r = (Arange*)avlnext(r)){
if(b->logsz >= Logspc - Logslop){
a->nlog++;
nb = a->logbuf[a->lbidx++ % nelem(a->logbuf)];
if(nb->bp.addr != -1)
cachedel(nb->bp.addr);
initblk(nb, blks[i++], -1, Tlog);
b->logp = nb->bp;
setflag(b, Bdirty);
finalize(b);
syncblk(b);
b = nb;
}
p = b->data + b->logsz;
PACK64(p+0, r->off|LogFree);
PACK64(p+8, r->len);
setflag(b, Bdirty);
b->logsz += 16;
setflag(b, Bdirty);
}
finalize(b);
syncblk(b);
/*
* now we have a valid freelist, and we can start
* appending stuff to it. Clean up the old logs
* and the eagerly allocated extra blocks.
*/
a->loghd = hd;
a->logtl = b;
for(; i < nblks; i++){
cachedel(b->bp.addr);
blkdealloc_lk(a, blks[i]);
}
poperror();
free(blks);
return 0;
}
int
syncbarrier(Arena *a, vlong gen)
{
logappend(a, gen<<8, 0, LogSync);
if(a->loghd.addr == -1)
a->loghd = a->logtl->bp;
return 0;
}
/*
* Allocate from an arena, with lock
* held. May be called multiple times
* per operation, to alloc space for
* the alloc log.
*/
static vlong
blkalloc_lk(Arena *a, int force)
{
Avltree *t;
Arange *r;
vlong b;
t = a->free;
r = (Arange*)t->root;
if(!force && a->size - a->used <= a->reserve)
return -1;
if(r == nil)
broke(Estuffed);
/*
* A bit of sleight of hand here:
* while we're changing the sorting
* key, but we know it won't change
* the sort order because the tree
* covers disjoint ranges
*/
b = r->off;
r->len -= Blksz;
r->off += Blksz;
if(r->len == 0){
avldelete(t, r);
free(r);
}
a->used += Blksz;
return b;
}
static void
blkdealloc_lk(Arena *a, vlong b)
{
logappend(a, b, Blksz, LogFree);
if(a->loghd.addr == -1)
a->loghd = a->logtl->bp;
freerange(a->free, b, Blksz);
a->used -= Blksz;
}
void
blkdealloc(vlong b)
{
Arena *a;
a = getarena(b);
qlock(a);
blkdealloc_lk(a, b);
qunlock(a);
}
static vlong
blkalloc(int ty, uint hint)
{
Arena *a;
vlong b;
int tries;
tries = 0;
Again:
a = pickarena(ty, hint, tries);
if(tries == fs->narena)
error(Efull);
/*
* TODO: there's an extreme edge case
* here.
*
* If the file system has room to alloc
* a data block but no log block, then
* we end up with it in a stuck state.
* The fix is to reserve alloc blocks,
* so that we're guaranteed to be able
* to log an alloc if the disk is working
* correctly.
*/
tries++;
if(tries < fs->narena){
if(canqlock(a) == 0)
goto Again;
}else
qlock(a);
if(waserror()){
qunlock(a);
nexterror();
}
if((b = blkalloc_lk(a, 0)) == -1){
qunlock(a);
poperror();
goto Again;
}
logappend(a, b, Blksz, LogAlloc);
if(a->loghd.addr == -1)
a->loghd = a->logtl->bp;
qunlock(a);
poperror();
return b;
}
static Blk*
initblk(Blk *b, vlong bp, vlong gen, int ty)
{
Blk *ob;
ob = cacheget(bp);
if(ob != nil)
fatal("double alloc: %#p %B %#p %B", b, b->bp, ob, ob->bp);
b->type = ty;
b->bp.addr = bp;
b->bp.hash = -1;
b->bp.gen = gen;
switch(ty){
case Tdat:
b->data = b->buf;
break;
case Tarena:
b->data = b->buf+2;
break;
case Tdlist:
case Tlog:
b->logsz = 0;
b->logp = (Bptr){-1, -1, -1};
b->data = b->buf + Loghdsz;
break;
case Tpivot:
b->data = b->buf + Pivhdsz;
break;
case Tleaf:
b->data = b->buf + Leafhdsz;
break;
}
b->fnext = nil;
setflag(b, Bdirty);
b->nval = 0;
b->valsz = 0;
b->nbuf = 0;
b->bufsz = 0;
b->logsz = 0;
b->alloced = getcallerpc(&b);
return b;
}
Blk*
newblk(Tree *t, int ty, vlong hint)
{
vlong bp;
Blk *b;
bp = blkalloc(ty, hint);
b = cachepluck();
initblk(b, bp, t->memgen, ty);
b->alloced = getcallerpc(&t);
return b;
}
Blk*
dupblk(Tree *t, Blk *b)
{
Blk *r;
if((r = newblk(t, b->type, 0)) == nil)
return nil;
setflag(r, Bdirty);
r->bp.hash = -1;
r->nval = b->nval;
r->valsz = b->valsz;
r->nbuf = b->nbuf;
r->bufsz = b->bufsz;
r->logsz = b->logsz;
r->alloced = getcallerpc(&t);
memcpy(r->buf, b->buf, sizeof(r->buf));
return r;
}
void
finalize(Blk *b)
{
if(b->type != Tdat)
PACK16(b->buf, b->type);
switch(b->type){
default:
abort();
break;
case Tpivot:
PACK16(b->buf+2, b->nval);
PACK16(b->buf+4, b->valsz);
PACK16(b->buf+6, b->nbuf);
PACK16(b->buf+8, b->bufsz);
break;
case Tleaf:
PACK16(b->buf+2, b->nval);
PACK16(b->buf+4, b->valsz);
break;
case Tdlist:
case Tlog:
b->logh = bufhash(b->data, b->logsz);
PACK16(b->buf+2, b->logsz);
PACK64(b->buf+4, b->logh);
packbp(b->buf+12, Ptrsz, &b->logp);
break;
case Tdat:
case Tarena:
case Tsuper:
break;
}
b->bp.hash = blkhash(b);
setflag(b, Bfinal);
cacheins(b);
b->cached = getcallerpc(&b);
}
Blk*
getblk(Bptr bp, int flg)
{
uvlong xh, ck;
Blk *b;
int i;
i = ihash(bp.addr) % nelem(fs->blklk);
qlock(&fs->blklk[i]);
if(waserror()){
qunlock(&fs->blklk[i]);
nexterror();
}
if((b = cacheget(bp.addr)) != nil){
b->lasthold = getcallerpc(&bp);
qunlock(&fs->blklk[i]);
poperror();
return b;
}
b = readblk(bp.addr, flg);
b->alloced = getcallerpc(&bp);
b->bp.hash = blkhash(b);
if((flg&GBnochk) == 0){
if(b->type == Tlog || b->type == Tdlist){
xh = b->logh;
ck = bufhash(b->data, b->logsz);
}else{
xh = bp.hash;
ck = b->bp.hash;
}
if(ck != xh)
broke("%s: %llux != %llux", Ecorrupt, xh, ck);
}
b->bp.gen = bp.gen;
b->lasthold = getcallerpc(&bp);
cacheins(b);
qunlock(&fs->blklk[i]);
poperror();
return b;
}
Blk*
holdblk(Blk *b)
{
ainc(&b->ref);
b->lasthold = getcallerpc(&b);
return b;
}
void
dropblk(Blk *b)
{
assert(b == nil || b->ref > 0);
if(b == nil || adec(&b->ref) != 0)
return;
b->lastdrop = getcallerpc(&b);
/*
* freed blocks go to the LRU bottom
* for early reuse.
*/
if(checkflag(b, Bfreed))
lrubot(b);
else
lrutop(b);
}
ushort
blkfill(Blk *b)
{
switch(b->type){
case Tpivot:
return 2*b->nbuf + b->bufsz + 2*b->nval + b->valsz;
case Tleaf:
return 2*b->nval + b->valsz;
default:
fprint(2, "invalid block @%lld\n", b->bp.addr);
abort();
}
return 0; // shut up kencc
}
void
limbo(Bfree *f)
{
Bfree *p;
ulong ge;
while(1){
ge = agetl(&fs->epoch);
p = agetp(&fs->limbo[ge]);
f->next = p;
if(acasp(&fs->limbo[ge], p, f)){
aincl(&fs->nlimbo, 1);
break;
}
}
}
void
freeblk(Tree *t, Blk *b, Bptr bp)
{
Bfree *f;
if(t == &fs->snap || (t != nil && bp.gen <= t->gen)){
killblk(t, bp);
return;
}
f = emalloc(sizeof(Bfree), 0);
f->op = DFblk;
f->bp = bp;
f->b = nil;
if(b != nil){
setflag(b, Blimbo);
b->freed = getcallerpc(&t);
f->b = holdblk(b);
}
limbo(f);
}
void
epochstart(int tid)
{
ulong ge;
ge = agetl(&fs->epoch);
asetl(&fs->lepoch[tid], ge | Eactive);
}
void
epochend(int tid)
{
ulong le;
le = agetl(&fs->lepoch[tid]);
asetl(&fs->lepoch[tid], le &~ Eactive);
}
void
epochwait(void)
{
int i, delay;
ulong e, ge;
delay = 0;
Again:
ge = agetl(&fs->epoch);
for(i = 0; i < fs->nworker; i++){
e = agetl(&fs->lepoch[i]);
if((e & Eactive) && e != (ge | Eactive)){
if(delay < 100)
delay++;
else
fprint(2, "stalled epoch %lx [worker %d]\n", e, i);
sleep(delay);
goto Again;
}
}
}
void
epochclean(void)
{
ulong c, e, ge;
Bfree *p, *n;
Arena *a;
Qent qe;
int i;
c = agetl(&fs->nlimbo);
ge = agetl(&fs->epoch);
for(i = 0; i < fs->nworker; i++){
e = agetl(&fs->lepoch[i]);
if((e & Eactive) && e != (ge | Eactive)){
if(c < fs->cmax/4)
return;
epochwait();
}
}
epochwait();
p = asetp(&fs->limbo[(ge+1)%3], nil);
asetl(&fs->epoch, (ge+1)%3);
for(; p != nil; p = n){
n = p->next;
switch(p->op){
case DFtree:
free(p->t);
break;
case DFblk:
a = getarena(p->bp.addr);
qe.op = Qfree;
qe.bp = p->bp;
qe.b = nil;
qput(a->sync, qe);
if(p->b != nil){
clrflag(p->b, Blimbo);
setflag(p->b, Bfreed);
dropblk(p->b);
}
break;
default:
abort();
}
aincl(&fs->nlimbo, -1);
free(p);
}
}
void
enqueue(Blk *b)
{
Arena *a;
Qent qe;
b->enqueued = getcallerpc(&b);
a = getarena(b->bp.addr);
assert(checkflag(b, Bdirty));
assert(b->bp.addr >= 0);
holdblk(b);
finalize(b);
setflag(b, Bqueued);
b->queued = getcallerpc(&b);
qe.op = Qwrite;
qe.bp = b->bp;
qe.b = b;
qput(a->sync, qe);
}
void
qinit(Syncq *q)
{
q->fullrz.l = &q->lk;
q->emptyrz.l = &q->lk;
q->nheap = 0;
q->heapsz = fs->cmax;
q->heap = emalloc(q->heapsz*sizeof(Qent), 1);
}
int
qcmp(Qent *a, Qent *b)
{
if(a->qgen != b->qgen)
return (a->qgen < b->qgen) ? -1 : 1;
if(a->bp.addr != b->bp.addr)
return (a->bp.addr < b->bp.addr) ? -1 : 1;
if(a->op != b->op){
if(a->op == Qfence)
return -1;
if(a->op == Qfree)
return 1;
}
return 0;
}
void
qput(Syncq *q, Qent qe)
{
int i;
if(qe.op == Qfree || qe.op == Qwrite)
assert((qe.bp.addr & (Blksz-1)) == 0);
else if(qe.op == Qfence)
assert(fs->syncing > 0);
else
abort();
qlock(&q->lk);
qe.qgen = agetv(&fs->qgen);
while(q->nheap == q->heapsz)
rsleep(&q->fullrz);
for(i = q->nheap; i > 0; i = (i-1)/2){
if(qcmp(&qe, &q->heap[(i-1)/2]) == 1)
break;
q->heap[i] = q->heap[(i-1)/2];
}
q->heap[i] = qe;
q->nheap++;
rwakeup(&q->emptyrz);
qunlock(&q->lk);
}
static Qent
qpop(Syncq *q)
{
int i, l, r, m;
Qent e, t;
qlock(&q->lk);
while(q->nheap == 0)
rsleep(&q->emptyrz);
e = q->heap[0];
if(--q->nheap == 0)
goto Out;
i = 0;
q->heap[0] = q->heap[q->nheap];
while(1){
m = i;
l = 2*i+1;
r = 2*i+2;
if(l < q->nheap && qcmp(&q->heap[m], &q->heap[l]) == 1)
m = l;
if(r < q->nheap && qcmp(&q->heap[m], &q->heap[r]) == 1)
m = r;
if(m == i)
break;
t = q->heap[m];
q->heap[m] = q->heap[i];
q->heap[i] = t;
i = m;
}
Out:
rwakeup(&q->fullrz);
qunlock(&q->lk);
if(e.b != nil){
clrflag(e.b, Bqueued);
e.b->queued = 0;
}
return e;
}
void
runsync(int, void *p)
{
Arena *a;
Syncq *q;
Qent qe;
q = p;
while(1){
qe = qpop(q);
switch(qe.op){
case Qfree:
a = getarena(qe.bp.addr);
qlock(a);
cachedel(qe.bp.addr);
blkdealloc_lk(a, qe.bp.addr);
if(qe.b != nil)
dropblk(qe.b);
qunlock(a);
break;
case Qfence:
qlock(&fs->synclk);
if(--fs->syncing == 0)
rwakeupall(&fs->syncrz);
qunlock(&fs->synclk);
break;
case Qwrite:
if(checkflag(qe.b, Bfreed) == 0)
syncblk(qe.b);
dropblk(qe.b);
break;
default:
abort();
}
assert(estacksz() == 0);
}
}
void
sync(void)
{
uvlong gen;
Arena *a;
Qent qe;
int i;
if(fs->rdonly)
return;
qlock(&fs->synclk);
if(!fs->snap.dirty){
qunlock(&fs->synclk);
return;
}
if(waserror()){
fprint(2, "failed to sync: %s\n", errmsg());
qunlock(&fs->synclk);
nexterror();
}
flushdlcache(1);
gen = aincv(&fs->qgen, 1);
fs->syncing = fs->nsyncers;
for(i = 0; i < fs->nsyncers; i++){
qe.op = Qfence;
qe.bp.addr = 0;
qe.bp.hash = -1;
qe.bp.gen = -1;
qe.b = nil;
qput(&fs->syncq[i], qe);
}
while(fs->syncing != 0)
rsleep(&fs->syncrz);
/* pass 0: sync arena contents */
for(i = 0; i < fs->narena; i++){
a = &fs->arenas[i];
qlock(a);
syncbarrier(a, gen);
finalize(a->logtl);
syncblk(a->logtl);
qunlock(a);
}
/*
* pass 1: sync block headers; if we crash here,
* the block footers are consistent, and we can
* use them.
*/
for(i = 0; i < fs->narena; i++){
a = &fs->arenas[i];
qlock(a);
packarena(a->h0->data, Blksz, a);
finalize(a->h0);
syncblk(a->h0);
qunlock(a);
}
/*
* pass 2: sync superblock; we have a consistent
* set of block headers, so if we crash, we can
* use the loaded block headers; the footers will
* get synced after so that we can use them next
* time around.
*/
for(i = 0; i < fs->narena; i++)
fs->arenabp[i] = fs->arenas[i].h0->bp;
packsb(fs->sb0->buf, Blksz, fs);
packsb(fs->sb1->buf, Blksz, fs);
finalize(fs->sb0);
finalize(fs->sb1);
syncblk(fs->sb0);
syncblk(fs->sb1);
fs->snap.dirty = 0;
/*
* pass 3: sync block footers; if we crash here,
* the block headers are consistent, and we can
* use them.
*/
for(i = 0; i < fs->narena; i++){
a = &fs->arenas[i];
qlock(a);
packarena(a->h1->data, Blksz, a);
finalize(a->h1);
syncblk(a->h1);
qunlock(a);
}
/*
* Pass 4: clean up the old snap tree's deadlist
*/
freedl(&fs->snapdl, 1);
fs->snapdl.hd.addr = -1;
fs->snapdl.hd.hash = -1;
fs->snapdl.hd.gen = -1;
fs->snapdl.tl.addr = -1;
fs->snapdl.tl.hash = -1;
fs->snapdl.tl.gen = -1;
fs->snapdl.ins = nil;
qunlock(&fs->synclk);
poperror();
}