btrfs: fix get set label blocking against balance
btrfs_ioctl_get_fslabel() and btrfs_ioctl_set_fslabel()
used root->fs_info->volume_mutex mutex which caused operations
like balance to block set/get label operation until its
completion and generally balance operation takes a long
time to complete, so it will be annoying to the user when
cli appears hung
also this patch will add a bit of optimization within
the btrfs_ioctl_get_falabel() function.
v1->v2:
use fs_info->super_lock instead of uuid_mutex
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f856c97..556b3d5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4042,18 +4042,22 @@
static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
{
struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
- const char *label = root->fs_info->super_copy->label;
- size_t len = strnlen(label, BTRFS_LABEL_SIZE);
+ size_t len;
int ret;
+ char label[BTRFS_LABEL_SIZE];
+
+ spin_lock(&root->fs_info->super_lock);
+ memcpy(label, root->fs_info->super_copy->label, BTRFS_LABEL_SIZE);
+ spin_unlock(&root->fs_info->super_lock);
+
+ len = strnlen(label, BTRFS_LABEL_SIZE);
if (len == BTRFS_LABEL_SIZE) {
pr_warn("btrfs: label is too long, return the first %zu bytes\n",
--len);
}
- mutex_lock(&root->fs_info->volume_mutex);
ret = copy_to_user(arg, label, len);
- mutex_unlock(&root->fs_info->volume_mutex);
return ret ? -EFAULT : 0;
}
@@ -4082,18 +4086,18 @@
if (ret)
return ret;
- mutex_lock(&root->fs_info->volume_mutex);
trans = btrfs_start_transaction(root, 0);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out_unlock;
}
+ spin_lock(&root->fs_info->super_lock);
strcpy(super_block->label, label);
+ spin_unlock(&root->fs_info->super_lock);
ret = btrfs_end_transaction(trans, root);
out_unlock:
- mutex_unlock(&root->fs_info->volume_mutex);
mnt_drop_write_file(file);
return ret;
}