Btrfs: make sure there are not any read requests before stopping workers

In close_ctree(), after we have stopped all workers,there maybe still
some read requests(for example readahead) to submit and this *maybe* trigger
an oops that user reported before:

kernel BUG at fs/btrfs/async-thread.c:619!

By hacking codes, i can reproduce this problem with one cpu available.
We fix this potential problem by invalidating all btree inode pages before
stopping all workers.

Thanks to Miao for pointing out this problem.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d3bd34e434f62f038f23599d920173f42931f405..f4e708239c09302e1ae84c59df2109cb135731b4 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3657,6 +3657,11 @@ int close_ctree(struct btrfs_root *root)
 
        btrfs_free_block_groups(fs_info);
 
+       /*
+        * we must make sure there is not any read request to
+        * submit after we stopping all workers.
+        */
+       invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
        btrfs_stop_all_workers(fs_info);
 
        free_root_pointers(fs_info, 1);