Messages in this thread | | | Date | Tue, 18 Oct 2005 22:58:05 -0400 | From | Chris Mason <> | Subject | Re: [PATCH] fix nr_unused accounting, and avoid recursing in iput with I_WILL_FREE set |
| |
On Tue, Oct 18, 2005 at 07:26:46PM -0700, Andrew Morton wrote: > > > hm, OK. It'd be nice to make that more explicit. Something like this? > > > > Well, I can't quite convince myself it is wrong, but when > > (!sb || (sb->s_flags & MS_ACTIVE), we're dropping the > > inode_lock with an inode with i_count == 0 and nr_unused hasn't been > > incremented. > > > > So, if someone (sync_sb_inodes?) comes in and runs __iget, > > the counts end up wrong. Then again, whoever ran __iget would also run > > iput and things would go horribly wrong anyway. > > Nope, it's equivalent:
The math ends up the same, but for your version there is a window where the lock isn't held and the count doesn't reflect reality. I don't know if anyone can race in and mess with the inode though. It is still on various lists, but if we're only in that part of generic_forget_inode during unmount, the super semaphore will keep out most potential racers.
I need to read harder.
> > Did I mention the part where Andrea and I are hunting a bug where the > > count of unused inodes goes negative and the everyone ends up spinning > > in shrink_icache_memory? > > No. > > > Andrea's patch doesn't fix the spinning, but > > it might have fixed the unused inode count going negative. We're > > waiting for another reproduce on the ppc64 race monster. > > I assume you have BUG_ON(inode_stat.nr_unused < 0)s in there everywhere? > > In fact WARN_ON(inode_stat.nr_unused < 100) might be better - something's > obviously doing a bogus decrement a lot of times. >
It goes negative in the invalidate_inodes run during unmount. I think Andrea's patch will solve that part, hopefully we'll know more tomorrow.
-chris
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |