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SubjectRe: Linux 2.4 quota (accounting?) bug ...
  Hi,

> On Sat, Oct 25, 2003 at 06:31:28PM +0200, Jan Kara wrote:
> > Hi,
> >
> > > a friend of mine, made me aware of the following
> > > imbalance, which looks like a minor accounting bug
> > > to me, but might be a quota bug ...
> > Sorry but the code seems correct to me - we get reference to dquot by
> > get_dquot_ref() and than we put the reference by dqput(). dqput() is
> > correct because something nasty might happen in the mean time and so we
> > might be the last holders of the dquot. What do you think is wrong?
>
> dqput() does dqstats.drops++;
> which isn't correct if this should be the same as
> put_dquot_ref(), but maybe I'm just irritated by
> strange statistics on some kernels showing more
> drops than lookups+allocated after sync/quotaoff
So I finally got to fixing the bug. The patch (also with a deletition
of unnecessary variable) is attached. Marcello please apply.

Honza

---------------------cut here-------------------------------------------

diff -ruX ../kerndiffexclude linux-2.4.22-um/fs/dquot.c linux-2.4.22-fixstat/fs/dquot.c
--- linux-2.4.22-um/fs/dquot.c Mon Aug 25 13:44:43 2003
+++ linux-2.4.22-fixstat/fs/dquot.c Wed Nov 5 21:21:58 2003
@@ -392,6 +392,7 @@
* is enough since if dquot is locked/modified it can't be
* on the free list */
get_dquot_ref(dquot);
+ dqstats.lookups++;
if (dquot->dq_flags & DQ_LOCKED)
wait_on_dquot(dquot);
if (dquot_dirty(dquot))
@@ -622,7 +623,6 @@
dqput(dquot);
return NODQUOT;
}
- ++dquot->dq_referenced;
dqstats.lookups++;

return dquot;
@@ -642,7 +642,6 @@
if (dquot->dq_flags & DQ_LOCKED)
printk(KERN_ERR "VFS: dqduplicate(): Locked quota to be duplicated!\n");
get_dquot_dup_ref(dquot);
- dquot->dq_referenced++;
dqstats.lookups++;

return dquot;
Only in linux-2.4.22-fixstat/include/linux: modules
diff -ruX ../kerndiffexclude linux-2.4.22-um/include/linux/quota.h linux-2.4.22-fixstat/include/linux/quota.h
--- linux-2.4.22-um/include/linux/quota.h Mon Aug 25 13:44:44 2003
+++ linux-2.4.22-fixstat/include/linux/quota.h Wed Nov 5 21:27:44 2003
@@ -222,8 +222,6 @@
loff_t dq_off; /* Offset of dquot on disk */
short dq_type; /* Type of quota */
short dq_flags; /* See DQ_* */
- unsigned long dq_referenced; /* Number of times this dquot was
- referenced during its lifetime */
struct mem_dqblk dq_dqb; /* Diskquota usage */
};

-
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