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Message-ID: <20130313105233.GB12012@gmail.com> Date: Wed, 13 Mar 2013 18:52:33 +0800 From: Zheng Liu <gnehzuil.liu@...il.com> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org Subject: Re: [BUG][dioread_nolock] blocked for more than 120s when we run xfstests #269 On Wed, Mar 13, 2013 at 10:15:11AM +0100, Jan Kara wrote: [snip] > > > I post the sysrq-w output here. But IMHO it is not very useful. So I > > > also post the sysrq-t output. > > Heh, curious. Thanks for the data. So worker thinks there's nothing to do > > but inode has elevated i_ioend_count... Maybe we leaked ioend somewhere. > > I'll check the code when I have time. > Ah, I think I see what's going on. > a) Code in ext4_ext_direct_IO() is racy wrt iocb->private handling (that > can get cleared concurrently from ext4_end_io_dio()). Thanks for tracing this problem. But I am still confused that iocb is allocated on stack in do_sync_write(), and is allocated from slab in ioctx_alloc(). You mean iocb in ext4_ext_direct_IO and ext4_end_io_dio is the same one? Then this iocb could be changed concurrently, and we are blocked for more than 120s. I must miss something. > b) ext4_end_io_dio() forgets to free the io_end if size == 0 (but this > shouldn't really happen looking into fs/direct_io.c). Yes, we will return directly from do_blockdev_direct_IO(). Regards, - Zheng -- 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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