ref: 2a5ba3cfc8748cd08bea89d93080948132f5aefe
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 */
/*
extents of Rawblocksize 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;
/* using nunits + 1 for alignment */
void
initmemunitpool(u64 nunits)
{
memunitstart = sbrk((nunits+1) * Rawblocksize);
memunitpool = memunitstart+Rawblocksize- ((u64)memunitstart%Rawblocksize);
initextents(&memunits);
if(chatty9p > 4)
dprint("initmemunitpool: memunitpool %p nunits*Rawblocksize %p\n",
memunitpool, nunits*Rawblocksize);
bfree(&memunits, 0, nunits);
}
u8 *
allocmemunit(void)
{
u64 m;
m = balloc(&memunits, 1);
if(chatty9p > 4)
dprint("allocmemunit: memunitpool %p m %p\n",
memunitpool, m);
return memunitpool+(m*Rawblocksize);
}
void
freememunit(u8 *m)
{
if(m == 0)
panic("freememunit: m == 0\n");
if((m-memunitpool)%Rawblocksize)
panic("freememunit: (m-memunitpool)%%Rawblocksize %llud\n",
(u64)(m-memunitpool)%Rawblocksize);
bfree(&memunits, (m-memunitpool)/Rawblocksize, 1);
}
/*
add an Iobuf to the collisions lru linked list
hp must be locked
*/
Iobuf *
newbuf(Hiob *hp)
{
Iobuf *p, *q;
p = emalloc9p(sizeof(Iobuf));
q = hp->link;
if(q != nil){
p->fore = q;
p->back = q->back;
q->back = p;
p->back->fore = p;
}else{
hp->link = p;
p->fore = p;
p->back = p;
}
p->blkno = 0;
p->xiobuf = allocmemunit();
return p;
}
/*
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, u8 readonly, u8 freshalloc)
{
Hiob *hp;
Iobuf *s, *p;
u64 ncollisions;
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, ncollisions = 0;;){
ncollisions++;
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(readonly){
if(chatty9p > 4)
dprint(" in cache iobuf 0x%p has blkno %llud .."
" rlock()\n", p, blkno);
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.
dirties is decremented without a wlock() on the buffer in dowrite().
Using a wlock() in dowrite() deadlocks with putwrite().
getbuf() guarantees that even a free'ed block cannot be
stolen until the dirties == 0. This avoids dirty blocks
being stolen by other block numbers.
incref(dirties) only happens with a wlock() in putwrite().
*/
if(ncollisions >= Ncollisions){
Another:
do{
p = s->back;
if(p->ref == 0 && p->dirties.ref == 0 && canwlock(p)){
if(p->dirties.ref > 0 || p->ref > 0){
wunlock(p);
goto Another;
}
hp->link = p;
if(chatty9p > 4)
dprint(" stealing iobuf 0x%p for blkno %llud\n",
p, blkno);
goto found; /* p is wlock() */
}
s = p;
}while(p != hp->link);
}
/* no unlocked blocks available; add a new one */
new:
if(chatty9p > 4)
dprint(" adding new Iobuf for blkno %llud\n", blkno);
p = newbuf(hp);
if(chatty9p > 4)
dprint(" .. wlock() blkno %llud\n", blkno);
wlock(p);
found:
p->blkno = blkno;
qunlock(hp);
if(chatty9p > 4)
dprint(" after qunlock(hp) hp 0x%p blkno %llud\n",
hp, blkno);
if(freshalloc == 0)
devread(blkno, p->xiobuf);
if(readonly){
if(chatty9p > 4)
dprint("new buffer: switching from wlock() to rlock() blkno %llud\n", blkno);
incref(p);
wunlock(p);
rlock(p);
decref(p);
}
return p;
}
Iobuf *
getbufchk(u64 blkno, u8 readonly, int tag, u64 qpath)
{
Iobuf *b;
if(chatty9p > 4)
dprint("getbufchk caller pc 0x%p\n", getcallerpc(&blkno));
b = getbuf(blkno, readonly, Bused);
if(b != nil)
if(checktag(b, tag, qpath) == 0){
putbuf(b);
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;
}
/*
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 = getbufchk(bno, Bwritable, Tdata, qpath);
if(buf == nil){
panic("bkp: buf == nil\n");
}
memcpy(buf->io->buf, contents, Blocksize);
if(qpath == Qproot0 || qpath == Qproot1){
buf->io->d.mode &= ~DMDIR; /* to avoid recursive du -a */
}
putbuf(buf);
}
void
putbuf(Iobuf *p)
{
s8 i;
u8 buf[Blocksize];
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);
if(p->readers){
chkrunlock(p);
if(chatty9p > 4)
dprint(" .. runlock()'ed\n");
}else{
if(canwlock(p)){
panic("putbuf: buffer not locked %llud\n", p->blkno);
}
srcbno = p->blkno;
if(p->blkno == config.config.srcbno ||
p->blkno == config.super.srcbno ||
p->blkno == config.root.srcbno){
memcpy(buf, p->io->buf, Blocksize);
}
putwrite(p);
if(srcbno == config.config.srcbno){
for(i=0; i<Nbkp; i++)
bkp(srcbno, buf, config.config.dest[i], Qpconfig0+i*3);
}else if(srcbno == config.super.srcbno){
for(i=0; i<Nbkp; i++)
bkp(srcbno, buf, config.super.dest[i], Qpsuper0+i*3);
}else if(srcbno == config.root.srcbno){
for(i=0; i<Nbkp; i++)
bkp(srcbno, buf, config.root.dest[i], Qproot0+i*3);
}
}
}
/* only caller is freeblockbuf().
These blocks do not need to be written to the disk.
Hence, avoiding putwrite().
*/
void
putbuffree(Iobuf *p)
{
if(p == nil){
panic("putbuffree p == nil called by %#p\n", getcallerpc(&p));
dprint("%s\n", errstring[Ephase]);
return;
}
if(p->io == nil){
showbuf(p);
panic("putbuffree p->io == nil by %#p\n", getcallerpc(&p));
dprint("%s\n", errstring[Ephase]);
return;
}
if(chatty9p > 4)
dprint("putbuffree p->blkno %llud\n", p->blkno);
if(p->readers){
chkrunlock(p);
// if(chatty9p > 4)
panic(" .. runlock()'ed\n");
}else{
if(canwlock(p)){
panic("putbuffree: buffer not locked %llud\n", p->blkno);
}
if(chkwunlock(p) == 0){
showbuf(p);
panic("putbuffree chkwunlock(p) == 0 called by %#p\n", getcallerpc(&p));
}
}
}
int
checktag(Iobuf *p, u16 tag, u64 qpath)
{
uintptr pc;
if(tag != p->io->type || (qpath != Qpnone && qpath != p->io->path)){
pc = getcallerpc(&p);
dprint(" tag = %G; expected %G; blkno = %llud\n",
(uint)p->io->type, (uint)tag, p->blkno);
if(qpath == Qpnone){
dprint("checktag pc=%p disk %s(block %llud) tag/path=%s/%llud;"
" expected %s\n",
pc, devfile, (u64)p->blkno,
tagnames[p->io->type], (u64)p->io->path,
tagnames[tag]);
} else {
dprint(" tag/path = %G/%llux; expected %G/%llux\n",
(uint)p->io->type, p->io->path, tag, qpath);
dprint("checktag pc=%p disk %s(block %llud) tag/path=%s/%llud;"
" expected %s/%llud\n",
pc, devfile, (u64)p->blkno,
tagnames[p->io->type], (u64)p->io->path,
tagnames[tag], (u64)qpath);
}
return 0;
}
return 1;
}
void
settag(Iobuf *p, int tagtype, u64 qpath)
{
if(p->readers)
panic("settag %s(%llux) tag/path=%s/%llud: not Bwritable\n",
devfile, (u64)p->blkno, tagnames[tagtype], qpath);
if(p->io == nil)
panic("settag %s(%llux) tag/path=%s/%llud: p->io == nil\n",
devfile, (u64)p->blkno, tagnames[tagtype], qpath);
p->io->type = tagtype;
p->io->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"
" fore 0x%p back 0x%p"
" xiobuf 0x%p"
" caller %#p\n",
p, p->ref, p->readers, p->writer,
p->blkno,
p->fore, p->back,
p->xiobuf,
getcallerpc(&p));
if(p->io != nil)
showblock(2, (u8*)p->io);
}