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gefs: fix fidtab locking order in clunkfid()

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Do not abuse fidtab lock for serializing
clunking.

The clunk should serialize on Fid.Lock
instead, so add a canlock check here.

The lock order is strictly:

Fid.Lock > Conn.fidtab[x].Lock
This commit is contained in:
cinap_lenrek 2024-08-30 19:16:13 +00:00
parent 0ab0a036ed
commit d31382ca17
1 changed files with 21 additions and 7 deletions
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28
sys/src/cmd/gefs/fs.c
View file

@ -769,12 +769,19 @@ dupfid(Conn *c, u32int new, Fid *f)
return n;
}
/*
* clunkfid() removes a fid from the
* connection fid tab and drops reference.
* Fid must be locked.
*/
static void
clunkfid(Conn *c, Fid *fid, Amsg **ao)
{
Fid *f, **pf;
u32int h;
assert(!canlock(fid));
h = ihash(fid->fid) % Nfidtab;
lock(&c->fidtablk[h]);
pf = &c->fidtab[h];
@ -786,6 +793,8 @@ clunkfid(Conn *c, Fid *fid, Amsg **ao)
}
pf = &f->next;
}
unlock(&c->fidtablk[h]);
assert(f != nil);
if(f->scan != nil){
free(f->scan);
@ -811,7 +820,6 @@ clunkfid(Conn *c, Fid *fid, Amsg **ao)
(*ao)->end = f->dent->length;
(*ao)->dent = f->dent;
}
unlock(&c->fidtablk[h]);
}
static int
@ -1796,8 +1804,8 @@ fsremove(Fmsg *m, int id, Amsg **ao)
}
t = f->mnt->root;
nm = 0;
*ao = nil;
lock(f);
*ao = nil;
clunkfid(m->conn, f, ao);
/* rclose files are getting removed here anyways */
if(*ao != nil)
@ -2291,7 +2299,7 @@ putconn(Conn *c)
{
Conn **pp;
Amsg *a;
Fid *f, *nf;
Fid *f;
int i;
if(adec(&c->ref) != 0)
@ -2313,19 +2321,25 @@ putconn(Conn *c)
close(c->cfd);
for(i = 0; i < Nfidtab; i++){
lock(&c->fidtablk[i]);
for(f = c->fidtab[i]; f != nil; f = nf){
nf = f->next;
for(;;){
lock(&c->fidtablk[i]);
f = c->fidtab[i];
if(f == nil){
unlock(&c->fidtablk[i]);
break;
}
ainc(&f->ref);
unlock(&c->fidtablk[i]);
lock(f);
a = nil;
clunkfid(c, f, &a);
unlock(f);
putfid(f);
if(a != nil)
chsend(fs->admchan, a);
}
unlock(&c->fidtablk[i]);
}
free(c);
}