ref: 4210fbecf4d94bd5873037bc3f5c721f47f42a2c
dir: /iobuf.c/
#include "all.h"
u64 nbuckets = 0; /* number of hash buckets, -m changes it */
Hiob *hiob = nil; /* array of nbuckets */
Extents frees = {0};/* extents of free blocks on the disk */
extern u8 synchronouswrites;
/*
extents of Blocksize units of memory used to store
the disk block contents in memory for the buffer cache
and write queue
*/
Extents memunits = {0};
u8 *memunitpool = nil;
u8 *memunitstart = nil;
static u64 lastflushtime = 0;
static RWLock flushlck;
/* using nunits + 1 for alignment */
void
initmemunitpool(u64 nunits)
{
memunitstart = sbrk((nunits+1) * Blocksize);
memunitpool = memunitstart+Blocksize- ((u64)memunitstart%Blocksize);
initextents(&memunits, "memunits");
if(chatty9p > 4)
dprint("initmemunitpool: memunitpool %p nunits*Blocksize %p\n",
memunitpool, nunits*Blocksize);
if(nunits > 0)
bfree(&memunits, 0, nunits);
else
panic("invalid nunits %llud\n", nunits);
}
u8 *
allocmemunits(u16 len)
{
u64 m;
u8 *a;
m = balloc(&memunits, len);
if(chatty9p > 4)
dprint("allocmemunit: memunitpool %p m %p\n",
memunitpool, m);
a = memunitpool+(m*Blocksize);
memset(a, 0, len*Blocksize);
return a;
}
void
freememunits(u8 *m, u16 len)
{
if(m == 0)
panic("freememunit: m == 0\n");
if((m-memunitpool)%Blocksize)
panic("freememunit: (m-memunitpool)%%Blocksize %llud\n",
(u64)(m-memunitpool)%Blocksize);
bfree(&memunits, (m-memunitpool)/Blocksize, len);
}
u64
flushold(void)
{
Iobuf *p;
Hiob *hp;
u64 nchecked, i;
nchecked = 0;
Again:
for(i = 0; i < nbuckets; i++){
hp=&hiob[i];
qlock(hp);
if((p = hp->link) != nil){
for(p = p->back; p != hp->link; p = p->back){
if(p->ref == 0 &&
p->atime < nsec()-Nrefresh){
if(canwlock(p)){
/* p->ref cannot change without a lock on the hash bucket */
if(p->atime > nsec()-Nrefresh){
wunlock(p);
continue;
}
incref(p); /* not needed */
/* remove p from its current position in the lru circular buffer */
p->back->fore = p->fore;
p->fore->back = p->back;
hp->n--;
qunlock(hp);
flush(p);
freememunits(p->xiobuf, p->len);
free(p);
goto Again;
}
}
}
}
nchecked++;
qunlock(hp);
}
return i==nbuckets;
}
u64
sync(void)
{
Iobuf *p, *s;
Hiob *hp;
u64 nlocked, i;
nlocked = 0;
for(i = 0; i < nbuckets; i++){
hp=&hiob[i];
qlock(hp);
if((s = hp->link) != nil){
p=s;
do{
if(p->xiobuf[0] == Tdentry &&
p->append != nil){
if(canwlock(p)){
qunlock(hp);
if(flush(p) == 0)
wunlock(p);
qlock(hp);
}else{
// cannot be sure about this without a lock
// if(p->xiobuf[0] == Tdentry)
nlocked++;
}
}
p = p->back;
}while(p != s);
}
qunlock(hp);
}
return nlocked;
}
/*
Get the Iobuf of the disk block at addr from the buffer cache
for my use.
All disk accesses go through the buffer cache. getbuf() selects
the Iobuf for our use from the buffer cache. putbuf() returns the
Iobuf back to the buffer cache.
Any Iobuf access happens only between the getbuf() and putbuf() calls.
The Iobuf's are grouped into a least-recently-used circular list
of buffers. The most recently used Iobuf is pointed to by Hiob.link.
Iobuf.fore is the next recently used buffer.
Iobuf.back is the oldest recently used buffer.
Hiob.link->back is the oldest buffer that will be reused first.
*/
Iobuf *
getbuf(u64 blkno, u16 len, u8 readonly, u8 freshalloc)
{
Hiob *hp;
Iobuf *s, *p;
hp = &hiob[blkno%nbuckets];
if(chatty9p > 4)
dprint("getbuf blkno %llud blkno%%nbuckets %llud pc 0x%p"
" hiob 0x%p hp 0x%p readonly %d\n",
blkno, blkno%nbuckets, getcallerpc(&blkno),
hiob, hp, readonly);
qlock(hp);
s = hp->link;
if(s == nil)
goto new;
for(p=s;;){
if(p->blkno == blkno){
if(p != s){
/* remove p from its current position in the lru circular buffer */
p->back->fore = p->fore;
p->fore->back = p->back;
/* make p the hb->link and put it at the back of existing link */
p->fore = s;
p->back = s->back;
s->back = p;
p->back->fore = p;
hp->link = p;
}
incref(p);
qunlock(hp);
if(chatty9p > 4)
dprint(" in cache, after qunlock(hp) hp 0x%p blkno %llud\n",
hp, blkno);
if(p->len != len){
wlock(p);
/* has someone done this change already? */
if(p->len != len){
freememunits(p->xiobuf, p->len);
p->xiobuf = allocmemunits(len);
p->len = len;
p->freshalloc = freshalloc;
if(freshalloc == 0)
devread(blkno, p->xiobuf, len);
if(readonly){
if(chkwunlock(p) == 0){
showbuf(p);
panic("getbuf chkwunlock(p) == 0 called by %#p\n", getcallerpc(&blkno));
}
rlock(p);
}
}
}else if(readonly){
if(chatty9p > 4)
dprint(" in cache iobuf 0x%p has len %llud blkno %llud len %llud .."
" rlock()\n", p, p->len, blkno, len);
rlock(p);
}else{
wlock(p);
if(chatty9p > 4)
dprint(" after wlock() blkno %llud\n", blkno);
}
decref(p);
return p;
}
p = p->fore;
if(p == s)
break;
}
/* maxed out our allowed number of collisions,
try to steal an older Iobuf without any ref's and not in the write queue.
Ncollisions is a soft limit.
We are not moving the stolen buffer to the top of the circular linked list,
but, setting this stolen buffer as the lru. I figure it should not matter
much either way. If it does, there is a changelru() function to do so in the
git history that can be reused.
incref(Iobuf) only happens with a qlock(hash bucket).
*/
if(hp->n >= Ncollisions){
for(p = hp->link->back; p != hp->link; p = p->back){
if(p->ref == 0 && p->append != nil){
if(canwlock(p)){
/* p->ref cannot change without a lock on the hash bucket */
if(p->append != nil){
wunlock(p);
continue;
}
incref(p);
goto found; /* p is wlock() */
}
}
}
}
/* no unlocked blocks available; add a new one */
new:
if(chatty9p > 4)
dprint(" adding new Iobuf for blkno %llud\n", blkno);
p = emalloc9p(sizeof(Iobuf));
wlock(p);
incref(p);
hp->n++;
found:
p->blkno = blkno;
s = hp->link;
if(s != nil){
/* for stolen Iobuf */
if(p->fore != nil && p->back != nil){
/* remove p from its current position in the lru circular buffer */
p->back->fore = p->fore;
p->fore->back = p->back;
}
/* make p the hb->link and put it at the back of existing link */
p->fore = s;
p->back = s->back;
s->back = p;
p->back->fore = p;
}else{
p->fore = p;
p->back = p;
}
hp->link = p;
qunlock(hp);
if(chatty9p > 4)
dprint(" after qunlock(hp) hp 0x%p blkno %llud\n",
hp, blkno);
if(p->len != len){
if(p->len > 0)
freememunits(p->xiobuf, p->len);
p->xiobuf = allocmemunits(len);
p->len = len;
}else
memset(p->xiobuf, 0, p->len*Blocksize);
p->freshalloc = freshalloc;
if(freshalloc == 0)
devread(blkno, p->xiobuf, len);
if(readonly){
wunlock(p);
rlock(p);
decref(p);
}
return p;
}
Iobuf *
getbufchk(u64 blkno, u16 len, u8 readonly, int tag, u64 qpath)
{
Iobuf *b;
if(chatty9p > 4)
dprint("getbufchk caller pc 0x%p\n", getcallerpc(&blkno));
b = getbuf(blkno, len, readonly, Bused);
if(b != nil)
if(tag > Tdata && tag < MAXTAG){
recentmetadata(b->m, &b->cur, &b->new);
if(readonly == 0){ /* writable */
memcpy(b->new, b->cur, Blocksize);
b->new->verd++;
}
}
if(checktag(b, len, tag, qpath) == 0){
putbuf(b, 0);
panic("checktag on %llud failed %s\n", blkno, errstring[Ephase]);
}
if(b->io == nil)
panic("b->io == nil blkno %llud readonly %d tag %d"
" qpath %llud b->blkno %llud caller %#p\n",
blkno, readonly, tag, qpath, b->blkno,
getcallerpc(&blkno));
return b;
}
Iobuf *
getmetachk(u64 blkno, u8 readonly, int tag, u64 qpath)
{
return getbufchk(blkno, Metadataunits, readonly, tag, qpath);
}
Iobuf *
getmeta(u64 blkno, u8 readonly, u8 freshalloc)
{
Iobuf *b;
b = getbuf(blkno, Metadataunits, readonly, freshalloc);
if(b == nil)
return nil;
recentmetadata(b->m, &b->cur, &b->new);
if(readonly == 0){ /* writable */
memcpy(b->new, b->cur, Blocksize);
b->new->verd++;
}
return b;
}
/*
put the Iobuf of the disk block at addr back into
the buffer cache for others to use.
writes to disk if changed.
if(chatty9p > 4)
dprint("putbuf p->blkno 0x%d t->c->type %d devtab[t->c->type]->dc %c\n"
" p 0x%p p->readonly %d\n"
" p->xiobuf 0x%p",
p->blkno, t->c->type, devtab[t->c->type]->dc,
p, p->readonly, p->xiobuf);
*/
void
bkp(u64 srcbno, u8 *contents, u64 bno, u64 qpath)
{
Iobuf *buf;
if(bno == 0){
dprint("bkp %llud: invalid backup location %llud, qpath %llud\n",
srcbno, bno, qpath);
return;
}
buf = getmetachk(bno, Bwritable, Tdentry, qpath);
if(buf == nil){
panic("bkp: buf == nil\n");
}
memcpy(buf->new->buf, contents, Ddatasize);
buf->new->mtime = nsec();
// if(qpath == Qproot0 || qpath == Qproot1){
// buf->d->mode &= ~DMDIR; /* to avoid recursive du -a */
// }
putbuf(buf, 1);
}
void
putbuf(Iobuf *p, u8 dowrite)
{
u8 buf[Ddatasize];
u64 srcbno;
if(p == nil){
panic("putbuf p == nil called by %#p\n", getcallerpc(&p));
dprint("%s\n", errstring[Ephase]);
return;
}
if(p->io == nil){
showbuf(p);
panic("putbuf p->io == nil by %#p\n", getcallerpc(&p));
dprint("%s\n", errstring[Ephase]);
return;
}
if(chatty9p > 4)
dprint("putbuf p->blkno %llud\n", p->blkno);
p->atime = nsec();
if(p->readers){
chkrunlock(p);
if(chatty9p > 4)
dprint(" .. runlock()'ed\n");
}else{
srcbno = p->blkno;
if(dowrite){
if(p->xiobuf[0] == Tdata){
devwrite(p->blkno, p->xiobuf, p->len);
}else{
if(p->blkno == config.config.srcbno ||
p->blkno == config.super.srcbno ||
p->blkno == config.root.srcbno)
memcpy(buf, p->new->buf, Ddatasize);
if(p->freshalloc)
devwrite(p->blkno, p->xiobuf, Metadataunits);
else
devwrite(p->blkno+(p->new>p->cur?1:0), p->new, 1);
}
}else if(p->xiobuf[0] > Tdata && p->xiobuf[0] < MAXTAG){
/*
make the new->ver below the cur->ver so the new gets
overwritten on the next access instead of a memcpy() to
copy the contents over.
*/
p->new->verd = p->cur->verd-1;
}
if(chkwunlock(p) == 0){
showbuf(p);
panic("putbuf: chkwunlock(p) == 0 called by %#p\n", getcallerpc(&p));
}
if(dowrite){
if(srcbno == config.config.srcbno){
bkp(srcbno, buf, config.config.dest[0], Qpconfig0);
}else if(srcbno == config.super.srcbno){
bkp(srcbno, buf, config.super.dest[0], Qpsuper0);
}else if(srcbno == config.root.srcbno){
bkp(srcbno, buf, config.root.dest[0], Qproot0);
}
}
}
if(canwlock(&flushlck)){
if(lastflushtime < nsec()-Nrefresh){
flushold();
lastflushtime = nsec();
}else
wunlock(&flushlck);
}
}
int
checktag(Iobuf *p, u16 len, u8 tag, u64 qpath)
{
uintptr pc;
u16 ptag;
u64 pqpath;
if(tag == Tdata){
ptag = p->io->tag;
pqpath = p->io->path;
}else{
ptag = ((Dentry*)p->cur)->tag;
pqpath = ((Dentry*)p->cur)->path;
}
if(len != p->len ||
tag != ptag ||
(qpath != Qpnone && qpath != pqpath)){
pc = getcallerpc(&p);
dprint(" tag = %G; expected %G; blkno = %llud\n",
(uint)ptag, (uint)tag, p->blkno);
if(qpath == Qpnone){
dprint("checktag pc=%p disk %s(block %llud) tag/path=%s/%llud;"
" expected %s len %llud p->len %llud\n",
pc, devfile, (u64)p->blkno,
tagnames[ptag], (u64)pqpath,
tagnames[tag],
len, p->len);
} else {
dprint(" tag/path = %G/%llux; expected %G/%llux\n",
(uint)ptag, pqpath, tag, qpath);
dprint("checktag pc=%p disk %s(block %llud) tag/path=%s/%llud;"
" expected %s/%llud\n",
pc, devfile, (u64)p->blkno,
tagnames[ptag], (u64)pqpath,
tagnames[tag], (u64)qpath);
panic("checktag failed\n");
}
return 0;
}
return 1;
}
void
settag(Iobuf *p, u8 tag, u64 qpath)
{
if(p->readers)
panic("settag %s(%llux) tag/path=%s/%llud: not Bwritable\n",
devfile, (u64)p->blkno, tagnames[tag], qpath);
if(p->io == nil)
panic("settag %s(%llux) tag/path=%s/%llud: p->io == nil\n",
devfile, (u64)p->blkno, tagnames[tag], qpath);
if(tag == Tdata){
p->io->tag = Tdata;
p->io->path = qpath;
}else{
((Dentry*)p->new)->tag = tag;
((Dentry*)p->new)->path = qpath;
}
}
void *amalloc(u64 n){
void *p;
if(p = mallocalign(n, sizeof(u64), 0, 0))
memset(p, 0, n);
else
sysfatal("malloc: %r");
setmalloctag(p, getcallerpc(&n));
return p;
}
/*
* Prepare nbuckets of hash buckets. Each bucket will point to a
* linked list of collisions. The collisions are ordered into a
* least-recently-used (lru) linked list.
*/
void
iobufinit(void)
{
int i;
Hiob *hp;
while(prime(nbuckets) == 0)
nbuckets++;
if(chatty9p)
dprint("mafs: iobufinit %ud hash buckets\n", nbuckets);
hiob = amalloc(nbuckets*sizeof(Hiob));
hp = hiob;
if(chatty9p > 4)
dprint("iobufinit: hiob 0x%p\n", hiob);
for(i=0; i<nbuckets; i++){
qlock(hp);
qunlock(hp);
hp++;
}
}
void
showbuf(Iobuf *p)
{
if(p == nil){
dprint("showbuf p == nil called by %#p\n",
p, getcallerpc(&p));
return;
}
dprint("showbuf p 0x%p ref %d readers %d writer %d"
" blkno %llud len %d"
" fore 0x%p back 0x%p"
" xiobuf 0x%p"
" caller %#p\n",
p, p->ref, p->readers, p->writer,
p->blkno, p->len,
p->fore, p->back,
p->xiobuf,
getcallerpc(&p));
if(p->io != nil)
showblock(2, (u8*)p->io);
}