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authorJosh Boyer <jwboyer@redhat.com>2011-08-25 07:48:12 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-08-25 10:50:18 -0700
commite096d0c7e2e4e5893792db865dd065ac73cf1f00 (patch)
tree20e603f81a9f1a55d330cba670952b991d564e00 /fs/inode.c
parente33f2d238e2e53e264c758c0849423a9308eb63e (diff)
lockdep: Add helper function for dir vs file i_mutex annotation
Purely in-memory filesystems do not use the inode hash as the dcache tells us if an entry already exists. As a result, they do not call unlock_new_inode, and thus directory inodes do not get put into a different lockdep class for i_sem. We need the different lockdep classes, because the locking order for i_mutex is different for directory inodes and regular inodes. Directory inodes can do "readdir()", which takes i_mutex *before* possibly taking mm->mmap_sem (due to a page fault while copying the directory entry to user space). In contrast, regular inodes can be mmap'ed, which takes mm->mmap_sem before accessing i_mutex. The two cases can never happen for the same inode, so no real deadlock can occur, but without the different lockdep classes, lockdep cannot understand that. As a result, if CONFIG_DEBUG_LOCK_ALLOC is set, this can lead to false positives from lockdep like below: find/645 is trying to acquire lock: (&mm->mmap_sem){++++++}, at: [<ffffffff81109514>] might_fault+0x5c/0xac but task is already holding lock: (&sb->s_type->i_mutex_key#15){+.+.+.}, at: [<ffffffff81149f34>] vfs_readdir+0x5b/0xb4 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&sb->s_type->i_mutex_key#15){+.+.+.}: [<ffffffff8108ac26>] lock_acquire+0xbf/0x103 [<ffffffff814db822>] __mutex_lock_common+0x4c/0x361 [<ffffffff814dbc46>] mutex_lock_nested+0x40/0x45 [<ffffffff811daa87>] hugetlbfs_file_mmap+0x82/0x110 [<ffffffff81111557>] mmap_region+0x258/0x432 [<ffffffff811119dd>] do_mmap_pgoff+0x2ac/0x306 [<ffffffff81111b4f>] sys_mmap_pgoff+0x118/0x16a [<ffffffff8100c858>] sys_mmap+0x22/0x24 [<ffffffff814e3ec2>] system_call_fastpath+0x16/0x1b -> #0 (&mm->mmap_sem){++++++}: [<ffffffff8108a4bc>] __lock_acquire+0xa1a/0xcf7 [<ffffffff8108ac26>] lock_acquire+0xbf/0x103 [<ffffffff81109541>] might_fault+0x89/0xac [<ffffffff81149cff>] filldir+0x6f/0xc7 [<ffffffff811586ea>] dcache_readdir+0x67/0x205 [<ffffffff81149f54>] vfs_readdir+0x7b/0xb4 [<ffffffff8114a073>] sys_getdents+0x7e/0xd1 [<ffffffff814e3ec2>] system_call_fastpath+0x16/0x1b This patch moves the directory vs file lockdep annotation into a helper function that can be called by in-memory filesystems and has hugetlbfs call it. Signed-off-by: Josh Boyer <jwboyer@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/inode.c')
-rw-r--r--fs/inode.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/fs/inode.c b/fs/inode.c
index 73920d555c8..ec7924696a1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -848,16 +848,9 @@ struct inode *new_inode(struct super_block *sb)
}
EXPORT_SYMBOL(new_inode);
-/**
- * unlock_new_inode - clear the I_NEW state and wake up any waiters
- * @inode: new inode to unlock
- *
- * Called when the inode is fully initialised to clear the new state of the
- * inode and wake up anyone waiting for the inode to finish initialisation.
- */
-void unlock_new_inode(struct inode *inode)
-{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void lockdep_annotate_inode_mutex_key(struct inode *inode)
+{
if (S_ISDIR(inode->i_mode)) {
struct file_system_type *type = inode->i_sb->s_type;
@@ -873,7 +866,20 @@ void unlock_new_inode(struct inode *inode)
&type->i_mutex_dir_key);
}
}
+}
+EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
#endif
+
+/**
+ * unlock_new_inode - clear the I_NEW state and wake up any waiters
+ * @inode: new inode to unlock
+ *
+ * Called when the inode is fully initialised to clear the new state of the
+ * inode and wake up anyone waiting for the inode to finish initialisation.
+ */
+void unlock_new_inode(struct inode *inode)
+{
+ lockdep_annotate_inode_mutex_key(inode);
spin_lock(&inode->i_lock);
WARN_ON(!(inode->i_state & I_NEW));
inode->i_state &= ~I_NEW;