Commit 14358e6ddaed27499d7d366b3e65c3e46b39e1c4
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lockdep: annotate dir vs file i_mutex
On Mon, 2007-09-24 at 22:13 -0400, Steven Rostedt wrote: > The circular lock seems to be this: > > #1: > > sys_mmap2: down_write(&mm->mmap_sem); > nfs_revalidate_mapping: mutex_lock(&inode->i_mutex); > > > #0: > > vfs_readdir: mutex_lock(&inode->i_mutex); > - during the readdir (filldir64), we take a user fault (missing page?) > and call do_page_fault - > do_page_fault: down_read(&mm->mmap_sem); > > > So it does indeed look like a circular locking. Now the question is, "is > this a bug?". Looking like the inode of #1 must be a file or something > else that you can mmap and the inode of #0 seems it must be a directory. > I would say "no". > > Now if you can readdir on a file or mmap a directory, then this could be > an issue. > > Otherwise, I'd love to see someone teach lockdep about this issue! ;-) 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 <a.p.zijlstra@chello.nl>
Showing 2 changed files with 13 additions and 0 deletions Side-by-side Diff
fs/inode.c
| ... | ... | @@ -567,6 +567,18 @@ |
| 567 | 567 | |
| 568 | 568 | void unlock_new_inode(struct inode *inode) |
| 569 | 569 | { |
| 570 | +#ifdef CONFIG_DEBUG_LOCK_ALLOC | |
| 571 | + struct file_system_type *type = inode->i_sb->s_type; | |
| 572 | + /* | |
| 573 | + * ensure nobody is actually holding i_mutex | |
| 574 | + */ | |
| 575 | + mutex_destroy(&inode->i_mutex); | |
| 576 | + mutex_init(&inode->i_mutex); | |
| 577 | + if (inode->i_mode & S_IFDIR) | |
| 578 | + lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key); | |
| 579 | + else | |
| 580 | + lockdep_set_class(&inode->i_mutex, &type->i_mutex_key); | |
| 581 | +#endif | |
| 570 | 582 | /* |
| 571 | 583 | * This is special! We do not need the spinlock |
| 572 | 584 | * when clearing I_LOCK, because we're guaranteed |