lkml.org 
[lkml]   [2009]   [Sep]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH 0/4] kill-the-bkl/reiserfs: fix some lock dependency inversions
On Tue, Sep 15, 2009 at 01:33:42AM +0400, Alexander Beregalov wrote:
> > Hi Alexander,
> >
> > It should be fixed now, still in the following tree:
>
> Hi!
> Another one, similar:
> It is v2.6.31-3123-g99bc470 plus your 805031859(kill-the-bkl/reiserfs:
> panic in case of lock imbalance), UP.



Although I can't reproduce it, I think I see how that can happen.

On mount time, we have the following dependency:

reiserfs_lock -> bdev_mutex -> sysfs_mutex

which happens while calling journal_init_dev() because
we open the device there.

But also in case of mmap on a reiserfs filesystem we
may call reiserfs_readpages(), holding the reiserfs lock
while already holding mm->mmap_sem

The above dependency is then updated:

mmap_sem
|
|
------- reiserfs_lock -> bdev_mutex -> sysfs_mutex
And later, while doing a readdir() on a sysfs directory,
sysfs calls filldir, which might_fault, and then might grab
mmap_sem. filldir is called there while holding sys_mutex,
creating the new following dependency

sysfs_mutex -> mmap_sem

Hence the inversion.
It seems the deadlock can't ever happen, I even don't see
corner cases where it could happen.

But still, this dependency should disappear.

Could you please tell me if the following patch makes it shut down?

Otherwise, I may need your config. I don't know why, but I suspect
the lock_acquire(mmap_sem) in might_fault doesn't trigger needed the lockdep
check, although I have the appropriate debug config, at least it seems.
But anyway, it should also happen in my box but it doesn't...

Thanks!

The patch:

diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index d23d6d7..59f7a4c 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -2801,11 +2801,14 @@ int journal_init(struct super_block *sb, const char *j_dev_name,
goto free_and_return;
}

+ reiserfs_write_unlock(sb);
if (journal_init_dev(sb, journal, j_dev_name) != 0) {
reiserfs_warning(sb, "sh-462",
"unable to initialize jornal device");
+ reiserfs_write_lock(sb);
goto free_and_return;
}
+ reiserfs_write_lock(sb);

rs = SB_DISK_SUPER_BLOCK(sb);



\
 
 \ /
  Last update: 2009-09-16 22:41    [W:0.093 / U:0.064 seconds]
©2003-2014 Jasper Spaans. Advertise on this site