On Thu, 2007-09-27 at 15:00 +0100, Christoph Hellwig wrote:
> On Thu, Sep 27, 2007 at 03:51:07PM +0200, Peter Zijlstra wrote:
> > Christoph,
> >
> > does Steve's story make sense?
>
> Yes.
>
> > All that would need to be done is add an extra lock_class_key to
> > file_system_type for i_mutex_dir_key, and extend alloc_inode to say
> > something like:
> >
> > if (dir)
> > lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_dir_key);
> > else
> > lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
>
> Unfortunately we don't know what type of inode we have when calling
> alloc_inode. We only know it after reading in the inode from disk,
> aka in unlock_new_inode. Then again there is no reason to use
> i_mutex before unlock_new_inode returns, so maybe we could defer
> initializing it until unlock_new_inode. I'm pretty sure we'll have
> to fix a few filesystems that take i_mutex before that despite not
> needing it, e.g. through i_size_write, though.
How about this:
---
Make a distinction between file and dir usage of i_mutex.
The inode should be complete and unused at unlock_new_inode(), re-init
i_mutex depending on its type.
Signed-off-by: Peter Zijlstra <[email protected]>
---
fs/inode.c | 12 ++++++++++++
include/linux/fs.h | 1 +
2 files changed, 13 insertions(+)
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c
+++ linux-2.6/fs/inode.c
@@ -576,6 +576,18 @@ EXPORT_SYMBOL(new_inode);
void unlock_new_inode(struct inode *inode)
{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct file_system_type *type = inode->i_sb->s_type;
+ /*
+ * ensure nobody is actually holding i_mutex
+ */
+ mutex_destroy(&inode->i_mutex);
+ mutex_init(&inode->i_mutex);
+ if (inode->i_mode & S_IFDIR)
+ lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key);
+ else
+ lockdep_set_class(&inode->i_mutex, &type->i_mutex_key);
+#endif
/*
* This is special! We do not need the spinlock
* when clearing I_LOCK, because we're guaranteed
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h
+++ linux-2.6/include/linux/fs.h
@@ -1426,6 +1426,7 @@ struct file_system_type {
struct lock_class_key i_lock_key;
struct lock_class_key i_mutex_key;
+ struct lock_class_key i_mutex_dir_key;
struct lock_class_key i_alloc_sem_key;
};
-
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