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    SubjectRe: [2.6.22] circular lock detected
    On Mon, 3 Sep 2007 16:01:35 +0200 Jan Kara <jack@suse.cz> wrote:

    > On Mon 03-09-07 05:49:59, Andrew Morton wrote:
    > > > On Mon, 3 Sep 2007 14:27:02 +0200 Jan Kara <jack@suse.cz> wrote:
    > > > > > On Fri, 24 Aug 2007 23:00:33 +0200 Folkert van Heusden <folkert@vanheusden.com> wrote:

    > > > > Has been reported before, but I don't recall whether we fixed it. Jan,
    > > > > do you know>?
    > > > I think we at least found a solution: Teach lockdep that I_MUTEX for
    > > > different filesystems is different. Peter Zilstra wrote a patch for that
    > > > and Folkert even confirmed that it fixes the problem for him. I'm not
    > > > sure what happened with the patch afterwards though. Adding Peter to CC
    > > > :).
    > >
    > > But this is a tty_lock-versus-dqptr_sem ranking error. Unrelated to i_mutex?
    > The final report is for this ranking but the locking chain (if I understand it
    > right) is:
    > tty_mutex (con_close) -> i_mutex (sysfs: remove_subdir)
    > i_mutex (do_truncate) -> i_alloc_sem (notify_change) -> truncate_mutex (ext3_truncate)
    > truncate_mutex (ext3_get_blocks_handle) -> dqptr_sem (dquot_alloc_space)
    >
    > So it complains about tty_mutex vs dqptr_sem (I don't know why it does not
    > complain about tty_mutex vs i_mutex) but the wrong link in the chain is
    > that i_mutex from remove_subdir() [sysfs] and i_mutex from do_truncate()
    > [ext3] are different and should never depend on each other...
    >

    Found it again.

    ---

    Give each filesystem its own inode lock class. The various filesystems have
    different locking order wrt the inode locks; esp. the pseudo filesystems
    differ from the rest.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    fs/inode.c | 12 +++++++++---
    include/linux/fs.h | 5 +++++
    2 files changed, 14 insertions(+), 3 deletions(-)

    Index: linux-2.6/fs/inode.c
    ===================================================================
    --- linux-2.6.orig/fs/inode.c
    +++ linux-2.6/fs/inode.c
    @@ -142,6 +142,15 @@ static struct inode *alloc_inode(struct
    return NULL;
    }

    + spin_lock_init(&inode->i_lock);
    + lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
    +
    + mutex_init(&inode->i_mutex);
    + lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
    +
    + init_rwsem(&inode->i_alloc_sem);
    + lockdep_set_class(&inode->i_alloc_sem, &sb->s_type->i_alloc_sem_key);
    +
    mapping->a_ops = &empty_aops;
    mapping->host = inode;
    mapping->flags = 0;
    @@ -190,8 +199,6 @@ void inode_init_once(struct inode *inode
    INIT_HLIST_NODE(&inode->i_hash);
    INIT_LIST_HEAD(&inode->i_dentry);
    INIT_LIST_HEAD(&inode->i_devices);
    - mutex_init(&inode->i_mutex);
    - init_rwsem(&inode->i_alloc_sem);
    INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
    rwlock_init(&inode->i_data.tree_lock);
    spin_lock_init(&inode->i_data.i_mmap_lock);
    @@ -199,7 +206,6 @@ void inode_init_once(struct inode *inode
    spin_lock_init(&inode->i_data.private_lock);
    INIT_RAW_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
    INIT_LIST_HEAD(&inode->i_data.i_mmap_nonlinear);
    - spin_lock_init(&inode->i_lock);
    i_size_ordered_init(inode);
    #ifdef CONFIG_INOTIFY
    INIT_LIST_HEAD(&inode->inotify_watches);
    Index: linux-2.6/include/linux/fs.h
    ===================================================================
    --- linux-2.6.orig/include/linux/fs.h
    +++ linux-2.6/include/linux/fs.h
    @@ -1302,8 +1302,13 @@ struct file_system_type {
    struct module *owner;
    struct file_system_type * next;
    struct list_head fs_supers;
    +
    struct lock_class_key s_lock_key;
    struct lock_class_key s_umount_key;
    +
    + struct lock_class_key i_lock_key;
    + struct lock_class_key i_mutex_key;
    + struct lock_class_key i_alloc_sem_key;
    };

    extern int get_sb_bdev(struct file_system_type *fs_type,
    -
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