From: David Sterba Date: Thu, 15 Jun 2017 22:09:21 +0000 (+0200) Subject: btrfs: switch to RCU for device traversal in btrfs_ioctl_fs_info X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=d03262c75da97503d026516456da41f38aa82067;p=openwrt%2Fstaging%2Fblogic.git btrfs: switch to RCU for device traversal in btrfs_ioctl_fs_info 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 --- diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index f1884c075cd3..ab7ff3efcba6 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2749,16 +2749,16 @@ 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;