[PATCH 10/11] btrfs: switch to RCU for device traversal in btrfs_ioctl_fs_info
From: David Sterba <dsterba@suse.com>
Date: 2017-10-31 17:46:44
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
We don't need to use the mutex as we do not modify the devices nor the list itself and just read information about device counts. Move copying fsid out of the protected section, not applicable to RCU same as the rest of the retrieved information. Signed-off-by: David Sterba <dsterba@suse.com> --- fs/btrfs/ioctl.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f0a3308a72c5..b15973cde0b6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c@@ -2753,16 +2753,16 @@ static long btrfs_ioctl_fs_info(struct btrfs_fs_info *fs_info, if (!fi_args) return -ENOMEM; - mutex_lock(&fs_devices->device_list_mutex); + rcu_read_lock(); fi_args->num_devices = fs_devices->num_devices; - memcpy(&fi_args->fsid, fs_info->fsid, sizeof(fi_args->fsid)); - list_for_each_entry(device, &fs_devices->devices, dev_list) { + list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) { if (device->devid > fi_args->max_id) fi_args->max_id = device->devid; } - mutex_unlock(&fs_devices->device_list_mutex); + rcu_read_unlock(); + memcpy(&fi_args->fsid, fs_info->fsid, sizeof(fi_args->fsid)); fi_args->nodesize = fs_info->nodesize; fi_args->sectorsize = fs_info->sectorsize; fi_args->clone_alignment = fs_info->sectorsize;
--
2.14.0