[Linux-kernel-mentees] [PATCH] fs: btrfs: volumes.h: Annotate rcu_string with __rcu

madhuparnabhowmik04 at gmail.com madhuparnabhowmik04 at gmail.com
Wed Dec 4 20:19:01 UTC 2019

From: Madhuparna Bhowmik <madhuparnabhowmik04 at gmail.com>

This patch fixes the following sparse errors in
fs/btrfs/super.c in function btrfs_show_devname()

fs/btrfs/super.c: error: incompatible types in comparison expression (different address spaces):
fs/btrfs/super.c:    struct rcu_string [noderef] <asn:4> *
fs/btrfs/super.c:    struct rcu_string *

The error was because of the following line in function btrfs_show_devname():

if (first_dev)
       seq_escape(m, rcu_str_deref(first_dev->name), " \t\n\\");

rcu_str_deref is defined in fs/btrfs/rcu-string.h

And first_dev is of type struct btrfs_device.

struct btrfs_device is defined in fs/btrfs/volumes.h

Annotating the member  "struct rcu_string *name "  of struct btrfs_device
with __rcu fixes the sparse error.

Acked-by: Joel Fernandes (Google) <joel at joelfernandes.org>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04 at gmail.com>
 fs/btrfs/volumes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index a7da1f3e3627..de7131ee604d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -64,7 +64,7 @@ struct btrfs_device {
 	struct btrfs_fs_devices *fs_devices;
 	struct btrfs_fs_info *fs_info;
-	struct rcu_string *name;
+	struct rcu_string __rcu *name;
 	u64 generation;

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