Re: Oops: Quota race in 2.4.12?

From: Neil Brown (neilb@cse.unsw.edu.au)
Date: Mon Oct 29 2001 - 19:23:49 EST


On Sunday October 28, sim@netnation.com wrote:
> Some of our dual CPU web servers with 2.4.12 are Oopsing while running
> quotacheck.

And speaking of quota oopses, I have had oops while enabling quota on
an active filesystem (which admittedly isn't very smart, but shouldn't
oops).
I think the following patch fixes it for 2.4.13. I had a quick look
at the latest -ac code it doesn't have the same problem.

--------------------------------------------------------------------
Avoid Oops when quotas turned on on active filesystem

Current code
  sets quotas-enabled flag
  possibly blocks on dqget or dqput
  then sets dq_op

If other code call DQUOT_INIT (for example) during the block, it will oops.

--- ./fs/dquot.c 2001/10/30 00:17:23 1.1
+++ ./fs/dquot.c 2001/10/30 00:18:26 1.2
@@ -1363,6 +1363,7 @@
         inode->i_flags |= S_NOQUOTA;
 
         dqopt->files[type] = f;
+ sb->dq_op = &dquot_operations;
         set_enable_flags(dqopt, type);
 
         dquot = dqget(sb, 0, type);
@@ -1370,7 +1371,6 @@
         dqopt->block_expire[type] = (dquot != NODQUOT) ? dquot->dq_btime : MAX_DQ_TIME;
         dqput(dquot);
 
- sb->dq_op = &dquot_operations;
         add_dquot_ref(sb, type);
 
         up(&dqopt->dqoff_sem);

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