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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>
This commit is contained in:
Anand Jain 2013-07-19 17:39:32 +08:00 committed by Chris Mason
parent d4c34f6bff
commit a1b83ac52d
1 changed files with 10 additions and 6 deletions
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16
fs/btrfs/ioctl.c
View File

@ -4042,18 +4042,22 @@ static long btrfs_ioctl_set_received_subvol(struct file *file,
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 @@ static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
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;
}