We don't need to use the mutex as we do not modify the devices nor the
list itself and just read some information:
does not change during device lifetime:
- devid
- uuid
- name (ie. the path)
may change in parallel to the ioctl call, but can lead only to reporting
inacurracy:
- bytes_used
- total_bytes
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
fs/btrfs/ioctl.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index fd172a93d11a..f0a3308a72c5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2779,7 +2779,6 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
{
struct btrfs_ioctl_dev_info_args *di_args;
struct btrfs_device *dev;
- struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
int ret = 0;
char *s_uuid = NULL;
@@ -2790,7 +2789,7 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
if (!btrfs_is_empty_uuid(di_args->uuid))
s_uuid = di_args->uuid;
- mutex_lock(&fs_devices->device_list_mutex);
+ rcu_read_lock();
dev = btrfs_find_device(fs_info, di_args->devid, s_uuid, NULL);
if (!dev) {
@@ -2805,17 +2804,15 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
if (dev->name) {
struct rcu_string *name;
- rcu_read_lock();
name = rcu_dereference(dev->name);
strncpy(di_args->path, name->str, sizeof(di_args->path));
- rcu_read_unlock();
di_args->path[sizeof(di_args->path) - 1] = 0;
} else {
di_args->path[0] = '\0';
}
out:
- mutex_unlock(&fs_devices->device_list_mutex);
+ rcu_read_unlock();
if (ret == 0 && copy_to_user(arg, di_args, sizeof(*di_args)))
ret = -EFAULT;
--
2.14.0
--
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