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@xxxxxxxxx>
Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
---
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
