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Date: Fri, 26 Aug 2011 11:52:34 -0400 From: Ted Ts'o <tytso@....edu> To: Tao Ma <tm@....ma> Cc: Dave Chinner <david@...morbit.com>, Jiaying Zhang <jiayingz@...gle.com>, linux-ext4@...r.kernel.org Subject: 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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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