ref: bd1d74ba77fc8777d51038f65190ab3506bc1388
dir: /snap.c/
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <avl.h>
#include "dat.h"
#include "fns.h"
#include "atomic.h"
static void
dlsync(Dlist *dl)
{
char kvbuf[512];
Msg m;
if(dl->ins == nil)
return;
if(!checkflag(dl->ins, Bdirty))
return;
enqueue(dl->ins);
m.op = Oinsert;
dlist2kv(dl, &m, kvbuf, sizeof(kvbuf));
btupsert(&fs->snap, &m, 1);
}
static void
dlcachedel(Dlist *dl, int hdel)
{
uint h;
Dlist *d, **p;
h = ihash(dl->gen) ^ ihash(dl->bgen);
if(hdel){
p = &fs->dlcache[h % fs->dlcmax];
for(d = *p; d != nil; d = d->chain){
if(d->gen == dl->gen && d->bgen == dl->bgen)
break;
p = &d->chain;
}
if(d != nil)
*p = d->chain;
}
if(dl == fs->dlhead)
fs->dlhead = dl->cnext;
if(dl == fs->dltail)
fs->dltail = dl->cprev;
if(dl->cnext != nil)
dl->cnext->cprev = dl->cprev;
if(dl->cprev != nil)
dl->cprev->cnext = dl->cnext;
dl->cnext = nil;
dl->cprev = nil;
}
static Dlist*
dlcacheget(vlong gen, vlong bgen)
{
Dlist *dl;
uint h;
h = ihash(gen) ^ ihash(bgen);
for(dl = fs->dlcache[h % fs->dlcmax]; dl != nil; dl = dl->chain)
if(dl->gen == gen && dl->bgen == bgen)
break;
if(dl != nil)
dlcachedel(dl, 0);
return dl;
}
static Dlist*
getdl(vlong gen, vlong bgen)
{
char kbuf[Dlksz], kvbuf[Dlkvpsz];
Dlist *dl, **p;
uint h;
Msg m;
Kvp kv;
Key k;
if((dl = dlcacheget(gen, bgen)) != nil)
return dl;
dl = emalloc(sizeof(Dlist), 1);
if(waserror()){
free(dl);
nexterror();
}
kbuf[0] = Kdlist;
PACK64(kbuf+1, gen);
PACK64(kbuf+9, bgen);
k.k = kbuf;
k.nk = sizeof(kbuf);
/* load up existing dlist */
if(btlookup(&fs->snap, &k, &kv, kvbuf, sizeof(kvbuf))){
kv2dlist(&kv, dl);
if(dl->hd.addr != -1)
dl->ins = getblk(dl->hd, 0);
goto Found;
}
/* create a new one if it didn't exist */
dl->gen = gen;
dl->bgen = bgen;
dl->hd.addr = -1;
dl->tl.addr = -1;
dl->ins = nil;
m.op = Oinsert;
dlist2kv(dl, &m, kvbuf, sizeof(kvbuf));
btupsert(&fs->snap, &m, 1);
Found:
poperror();
h = ihash(gen) ^ ihash(bgen);
p = &fs->dlcache[h % fs->dlcmax];
dl->chain = *p;
*p = dl;
return dl;
}
void
putdl(Dlist *dl)
{
Dlist *dt;
if(dl == &fs->snapdl)
return;
dlcachedel(dl, 0);
while(fs->dltail != nil && fs->dlcount >= fs->dlcmax){
dt = fs->dltail;
dlsync(dt);
dlcachedel(dt, 1);
dropblk(dt->ins);
free(dt);
}
dl->cprev = nil;
dl->cnext = fs->dlhead;
if(fs->dltail == nil)
fs->dltail = dl;
if(fs->dlhead != nil)
fs->dlhead->cprev = dl;
fs->dlhead = dl;
}
void
freedl(Dlist *dl, int docontents)
{
char buf[Kvmax];
Bptr bp, fb;
Msg m;
Blk *b;
char *p;
bp = dl->hd;
if(dl != &fs->snapdl){
m.op = Odelete;
dlist2kv(dl, &m, buf, sizeof(buf));
btupsert(&fs->snap, &m, 1);
}
while(bp.addr != -1){
b = getblk(bp, 0);
if(docontents){
for(p = b->data; p != b->data+b->logsz; p += 8){
fb.addr = UNPACK64(p);
fb.hash = -1;
fb.gen = -1;
freeblk(nil, nil, fb);
}
}
bp = b->logp;
freeblk(&fs->snap, b, b->bp);
dropblk(b);
}
}
static void
mergedl(vlong merge, vlong gen, vlong bgen)
{
char buf[2][Kvmax];
Dlist *d, *m;
Msg msg[2];
Blk *b;
d = nil;
m = nil;
if(waserror()){
putdl(m);
putdl(d);
nexterror();
}
d = getdl(merge, bgen);
m = getdl(gen, bgen);
/*
* If the dest dlist didn't exist,
* just move the merge dlist over
* and be done with it, otherwise
* chain onto the existing dlist
* tail.
*/
if(d->hd.addr == -1){
assert(d->ins == nil);
d->hd = m->hd;
d->tl = m->tl;
d->ins = m->ins;
if(d->ins != nil)
holdblk(d->ins);
}else{
if(m->ins != nil && checkflag(m->ins, Bdirty))
enqueue(m->ins);
if(d->tl.addr == d->ins->bp.addr)
b = holdblk(d->ins);
else
b = getblk(d->tl, 0);
b->logp = m->hd;
setflag(b, Bdirty);
enqueue(b);
dropblk(b);
}
msg[0].op = Odelete;
dlist2kv(m, &msg[0], buf[0], sizeof(buf[0]));
msg[1].op = Oinsert;
dlist2kv(d, &msg[1], buf[1], sizeof(buf[1]));
btupsert(&fs->snap, msg, 2);
putdl(m);
putdl(d);
poperror();
}
static void
reclaimblocks(vlong gen, vlong succ, vlong prev)
{
char pfx[9];
Dlist dl;
Scan s;
pfx[0] = Kdlist;
PACK64(pfx+1, gen);
btnewscan(&s, pfx, sizeof(pfx));
btenter(&fs->snap, &s);
while(1){
if(!btnext(&s, &s.kv))
break;
kv2dlist(&s.kv, &dl);
if(succ != -1 && dl.bgen <= prev)
mergedl(succ, dl.gen, dl.bgen);
else if(dl.bgen <= prev)
mergedl(prev, dl.gen, dl.bgen);
else
freedl(&dl, 1);
}
btexit(&s);
}
/*
* Removes a label from a snapshot, allowing
* it to be reclaimed if it is not a direct
* predecessor of more than one other snapshot.
*
* If it has one successor and no label, then
* it will be merged with that successor.
*/
void
delsnap(Tree *t, vlong succ, char *name)
{
char *p, buf[4][Kvmax];
int nm, deltree;
Mount *mnt;
Msg m[4];
nm = 0;
deltree = 0;
if(name != nil){
if(strcmp(name, "dump") == 0
|| strcmp(name, "empty") == 0
|| strcmp(name, "adm") == 0)
error(Ename);
m[nm].op = Odelete;
m[nm].k = buf[nm];
p = packlbl(buf[nm], sizeof(buf[nm]), name);
m[nm].nk = p - m[nm].k;
m[nm].v = nil;
m[nm].nv = 0;
t->nlbl--;
nm++;
}
if(t->nlbl == 0 && t->nref <= 1){
deltree = 1;
m[nm].op = Orelink;
retag2kv(t->pred, succ, 0, 0, &m[nm], buf[nm], sizeof(buf[nm]));
nm++;
if(t->succ != -1){
m[nm].op = Oreprev;
retag2kv(t->succ, t->pred, 0, 0, &m[nm], buf[nm], sizeof(buf[nm]));
nm++;
}
m[nm].op = Odelete;
m[nm].k = buf[nm];
p = packsnap(buf[nm], sizeof(buf[nm]), t->gen);
m[nm].nk = p - m[nm].k;
m[nm].v = nil;
m[nm].nv = 0;
nm++;
}
assert(nm <= nelem(m));
flushdlcache(1);
btupsert(&fs->snap, m, nm);
reclaimblocks(t->gen, succ, t->pred);
if(deltree){
for(mnt = fs->mounts; mnt != nil; mnt = mnt->next){
if(mnt->root->gen == t->succ)
mnt->root->pred = t->pred;
if(mnt->root->gen == t->pred)
mnt->root->succ = t->succ;
}
}
}
/*
* Attaches a label to a tree, incrementing
* its reference count. This labelled snapshot
* will show up in the dump.
*/
void
tagsnap(Tree *t, char *name, int flg)
{
char buf[3][Kvmax];
Msg m[3];
Tree *n;
int i;
if(strcmp(name, "dump") == 0
|| strcmp(name, "empty") == 0
|| strcmp(name, "adm") == 0)
error(Ename);
i = 0;
n = nil;
if(waserror()){
free(n);
nexterror();
}
if(flg & Lmut){
n = emalloc(sizeof(Tree), 1);
n->memref = 1;
n->dirty = 0;
n->nlbl = 1;
n->nref = 0;
n->ht = t->ht;
n->bp = t->bp;
n->succ = -1;
n->pred = t->gen;
n->base = t->gen;
n->gen = aincv(&fs->nextgen, 1);
n->memgen = aincv(&fs->nextgen, 1);
t->nref++;
m[i].op = Orelink;
retag2kv(t->gen, t->succ, 0, 1, &m[i], buf[i], sizeof(buf[i]));
i++;
m[i].op = Oinsert;
lbl2kv(name, n->gen, flg, &m[i], buf[i], sizeof(buf[i]));
i++;
m[i].op = Oinsert;
tree2kv(n, &m[i], buf[i], sizeof(buf[i]));
i++;
}else{
t->nlbl++;
m[i].op = Orelink;
retag2kv(t->gen, t->succ, 1, 0, &m[i], buf[i], sizeof(buf[i]));
i++;
m[i].op = Oinsert;
t->pred = t->gen;
t->nlbl++;
lbl2kv(name, t->gen, flg, &m[i], buf[i], sizeof(buf[i]));
i++;
}
btupsert(&fs->snap, m, i);
poperror();
free(n);
}
/*
* Updates a snapshot; keeps the generation the same if possible,
* otherwise moves to a new generation. A snapshot may only stay
* at the same generation as long as it is at the tip of a snapshot
* list; once it's observable by a derived snapshot it must be
* immutable.
*/
void
updatesnap(Tree **r, Tree *o, char *lbl)
{
char buf[4][Kvmax];
Msg m[4];
Tree *t;
int i;
if(!o->dirty)
return;
/* update the old kvp */
o->nlbl--;
o->nref++;
/* create the new one */
t = emalloc(sizeof(Tree), 1);
if(waserror()){
free(t);
nexterror();
}
t->memref = 1;
t->dirty = 0;
t->nlbl = 1;
t->nref = 0;
t->ht = o->ht;
t->bp = o->bp;
t->succ = -1;
t->base = o->base;
t->gen = o->memgen;
t->memgen = aincv(&fs->nextgen, 1);
i = 0;
m[i].op = Orelink;
if(o->nlbl == 0 && o->nref == 1){
t->pred = o->pred;
retag2kv(t->pred, t->gen, 0, 0, &m[i], buf[i], sizeof(buf[i]));
}else{
t->pred = o->gen;
retag2kv(t->pred, t->gen, -1, 1, &m[i], buf[i], sizeof(buf[i]));
}
i++;
m[i].op = Oinsert;
tree2kv(t, &m[i], buf[i], sizeof(buf[i]));
i++;
m[i].op = Oinsert;
lbl2kv(lbl, t->gen, Lmut, &m[i], buf[i], sizeof(buf[i]));
i++;
btupsert(&fs->snap, m, i);
/* only update the dirty status after we sync */
o->dirty = 0;
/* this was the last ref to the snap */
if(o->nlbl == 0 && o->nref == 1)
delsnap(o, t->gen, nil);
closesnap(o);
asetp(r, t);
poperror();
}
/*
* open snapshot by label, returning a tree.
*/
Tree*
opensnap(char *label, int *mut)
{
char *p, buf[Kvmax];
Tree *t;
uint flg;
vlong gen;
Kvp kv;
Key k;
/* Klabel{"name"} => Ksnap{id} */
if((p = packlbl(buf, sizeof(buf), label)) == nil)
return nil;
k.k = buf;
k.nk = p - buf;
if(!btlookup(&fs->snap, &k, &kv, buf, sizeof(buf)))
return nil;
assert(kv.nv == 1+8+4);
gen = UNPACK64(kv.v + 1);
flg = UNPACK32(kv.v + 1+8);
if(mut != nil)
*mut = !!(flg&Lmut);
t = mallocz(sizeof(Tree), 1);
if(waserror()){
free(t);
nexterror();
}
p = packsnap(buf, sizeof(buf), gen);
k.k = buf;
k.nk = p - buf;
if(!btlookup(&fs->snap, &k, &kv, buf, sizeof(buf)))
broke(Efs);
unpacktree(t, kv.v, kv.nv);
t->memref = 1;
t->memgen = aincv(&fs->nextgen, 1);
poperror();
return t;
}
/*
* close snapshot, flushing and freeing in-memory
* representation.
*/
void
closesnap(Tree *t)
{
Bfree *f;
if(t == nil || adec(&t->memref) != 0)
return;
f = malloc(sizeof(Bfree));
f->op = DFtree;
f->t = t;
limbo(f);
}
void
flushdlcache(int clear)
{
Dlist *dl, *n;
for(dl = fs->dlhead; dl != nil; dl = n){
n = dl->cnext;
dlsync(dl);
if(clear){
if(dl->ins != nil)
dropblk(dl->ins);
free(dl);
}
}
if(clear){
fs->dlhead = nil;
fs->dltail = nil;
memset(fs->dlcache, 0, fs->dlcmax*sizeof(Dlist*));
}
}
/*
* Marks a block as killed by the tree
* t, which means that it will be free
* for use after t is reclaimed.
*
* t must be an active snapshot with
* no successors.
*/
void
killblk(Tree *t, Bptr bp)
{
Dlist *dl;
Blk *b;
char *p;
/*
* When we have a forked snap, blocks allocated before the fork
* are the responsibility of the other chain; in this chain, we
* leak it and let the last reference in the other chain clean up
*/
if(bp.gen <= t->base)
return;
if(t == &fs->snap)
dl = &fs->snapdl;
else
dl = getdl(t->gen, bp.gen);
if(waserror()){
putdl(dl);
nexterror();
}
if(dl->ins == nil || Logspc - dl->ins->logsz < Logslop){
b = newblk(&fs->snap, Tdlist, 0);
if(dl->ins != nil)
enqueue(dl->ins);
if(dl->tl.addr == -1)
dl->tl = b->bp;
b->logp = dl->hd;
dl->hd = b->bp;
dl->ins = b;
cacheins(b);
}
p = dl->ins->data + dl->ins->logsz;
dl->ins->logsz += 8;
setflag(dl->ins, Bdirty);
PACK64(p, bp.addr);
poperror();
putdl(dl);
}