Messages in this thread | | | Subject | Re: [PATCH] mm: backing-dev: use kfree_rcu() instead of synchronize_rcu_expedited() | From | zhangqiang <> | Date | Fri, 15 Oct 2021 11:39:40 +0800 |
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On 2021/10/14 下午7:24, Matthew Wilcox wrote: > On Thu, Oct 14, 2021 at 04:24:33PM +0800, Zqiang wrote: >> The bdi_remove_from_list() is called in RCU softirq, however the >> synchronize_rcu_expedited() will produce sleep action, use kfree_rcu() >> instead of it. >> >> Reported-by: Hao Sun <sunhao.th@gmail.com> >> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com> >> --- >> include/linux/backing-dev-defs.h | 1 + >> mm/backing-dev.c | 4 +--- >> 2 files changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h >> index 33207004cfde..35a093384518 100644 >> --- a/include/linux/backing-dev-defs.h >> +++ b/include/linux/backing-dev-defs.h >> @@ -202,6 +202,7 @@ struct backing_dev_info { >> #ifdef CONFIG_DEBUG_FS >> struct dentry *debug_dir; >> #endif >> + struct rcu_head rcu; >> }; > Instead of growing struct backing_dev_info, it seems to me this rcu_head > could be placed in a union with rb_node, since it will have been removed > from the bdi_tree by this point and the tree is never walked under > RCU protection? > Thanks for your advice, I find this bdi_tree is traversed under the protection of a spin lock, not under the protection of RCU. I find this modification does not avoid the problem described in patch, the flush_delayed_work() may be called in release_bdi() The same will cause problems.
may be we can replace queue_rcu_work() of call_rcu(&inode->i_rcu, i_callback) or do you have any better suggestions?
Thanks Zqiang
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