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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 <dsterba@suse.com>
This commit is contained in:
David Sterba 2017-06-16 00:09:21 +02:00
parent c5593ca3c8
commit d03262c75d
1 changed files with 4 additions and 4 deletions
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8
fs/btrfs/ioctl.c
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@ -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;