Re: [URGENT PATCH] ext4: fix potential deadlock in ext4_evict_inode()

On Fri, Aug 26, 2011 at 05:27:39PM +0800, Tao Ma wrote:

No, it doesn't mean the ext4_truncate. But another race pasted below.

Flush inode's i_completed_io_list before calling ext4_io_wait to
prevent the following deadlock scenario: A page fault happens while
some process is writing inode A. During page fault,
shrink_icache_memory is called that in turn evicts another inode
B. Inode B has some pending io_end work so it calls ext4_ioend_wait()
that waits for inode B's i_ioend_count to become zero. However, inode
B's ioend work was queued behind some of inode A's ioend work on the
same cpu's ext4-dio-unwritten workqueue. As the ext4-dio-unwritten
thread on that cpu is processing inode A's ioend work, it tries to
grab inode A's i_mutex lock. Since the i_mutex lock of inode A is
still hold before the page fault happened, we enter a deadlock.

... but that shouldn't be a problem since we're not holding A's
i_mutex at this point, right?  Or am I missing something?

	   	       	       	       - Ted