Messages in this thread Patch in this message | | | Date | Wed, 16 Sep 2009 22:37:50 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 0/4] kill-the-bkl/reiserfs: fix some lock dependency inversions |
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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);
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