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Subject: Re: mmotm 2011-06-22 - inconsistent {SOFTIRQ-ON-W} ->
 {IN-SOFTIRQ-W} usage.
From: Peter Zijlstra <peterz@infradead.org>
To: Valdis.Kletnieks@vt.edu
Cc: Jan Kara <jack@suse.cz>, stable@kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Jeff Garzik <jgarzik@pobox.com>,
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        linux-ide@vger.kernel.org
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Date: Thu, 23 Jun 2011 18:08:05 +0200
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On Thu, 2011-06-23 at 12:02 -0400, Valdis.Kletnieks@vt.edu wrote:
> On Thu, 23 Jun 2011 17:38:36 +0200, Peter Zijlstra said:
> > On Wed, 2011-06-22 at 21:59 -0400, Valdis.Kletnieks@vt.edu wrote:
> > > [   20.254275] {SOFTIRQ-ON-W} state was registered at:
> > > [   20.254275]   [<ffffffff8106973b>] mark_irqflags+0xf2/0x13e
> > > [   20.254275]   [<ffffffff810699b2>] __lock_acquire+0x22b/0x3e2
> > > [   20.254275]   [<ffffffff8106a09f>] lock_acquire+0x103/0x153
> > > [   20.254275]   [<ffffffff8157bb01>] _raw_spin_lock+0x36/0x45
> > > [   20.254275]   [<ffffffff8110ddf8>] end_writeback+0x33/0x103
> > > [   20.254275]   [<ffffffff81125425>] bdev_evict_inode+0x3e/0xbe
> > > [   20.254275]   [<ffffffff8110df78>] evict+0xb0/0x173
> > > [   20.254275]   [<ffffffff8110e1ea>] iput_final+0x171/0x17a
> > > [   20.254275]   [<ffffffff8110e241>] iput+0x4e/0x53
> > > [   20.254275]   [<ffffffff81125cad>] __blkdev_put+0x1c0/0x1eb
> > > [   20.254275]   [<ffffffff81125ebe>] blkdev_put+0x1e6/0x1f5
> > > [   20.254275]   [<ffffffff8121d143>] register_disk+0xea/0x13c
> > > [   20.254275]   [<ffffffff8121d2c4>] add_disk+0x12f/0x1a4
> > > [   20.254275]   [<ffffffff812ef339>] sd_probe_async+0x115/0x1b5
> > > [   20.254275]   [<ffffffff8105ce2f>] async_run_entry_fn+0x99/0x12a
> > > [   20.254275]   [<ffffffff810505e8>] process_one_work+0x25d/0x467
> > > [   20.254275]   [<ffffffff81051ddb>] worker_thread+0x152/0x206
> > > [   20.254275]   [<ffffffff810561fa>] kthread+0x7f/0x87
> > > [   20.254275]   [<ffffffff815835d4>] kernel_thread_helper+0x4/0x10=20
> > 
> > That looks broken. Not having -mm, is there a git tree some place?, I
> > cannot quite see how end_writeback() is taking mapping->tree_lock as my
> > version looks like:
> > 
> > void end_writeback(struct inode *inode)
> > {
> > 	might_sleep();
> > 	BUG_ON(inode->i_data.nrpages);
> > 	BUG_ON(!list_empty(&inode->i_data.private_list));
> 
> mm-fix-assertion-mapping-nrpages-==-0-in-end_writeback.patch does this:
> 
> diff -puN fs/inode.c~mm-fix-assertion-mapping-nrpages-==-0-in-end_writeback fs/inode.c
> --- a/fs/inode.c~mm-fix-assertion-mapping-nrpages-==-0-in-end_writeback
> +++ a/fs/inode.c
> @@ -423,7 +423,14 @@ EXPORT_SYMBOL(remove_inode_hash);
>  void end_writeback(struct inode *inode)
>  {
>         might_sleep();
> +       /*
> +        * We have to cycle tree_lock here because reclaim can be still in the
> +        * process of removing the last page (in __delete_from_page_cache())
> +        * and we must not free mapping under it.
> +        */
> +       spin_lock(&inode->i_data.tree_lock);
>         BUG_ON(inode->i_data.nrpages);
> +       spin_unlock(&inode->i_data.tree_lock);
>         BUG_ON(!list_empty(&inode->i_data.private_list));
>         BUG_ON(!(inode->i_state & I_FREEING));
>         BUG_ON(inode->i_state & I_CLEAR);
> 
> Adding Jan Kara to the list, and stable@kernel.org because the patch was cc'ed to there...

Yep, that very much wants to be spin_{un,}lock_irq().