Hi Jeff,
On 01/07/2013 07:24 AM, Jeff Liu wrote:
> Hi,
> On 01/07/2013 02:44 AM, Goffredo Baroncelli wrote:
>> Hi Jeff,
>>
>> On 01/05/2013 03:48 AM, Jeff Liu wrote:
>>> Add a new ioctl(2) BTRFS_IOC_GET_FSLABLE, so that we can get the label upon
>>> a mounted filesystem.
>>>
>>> Signed-off-by: Jie Liu <[email protected]>
>>> Signed-off-by: Anand Jain <[email protected]>
>>> Cc: Miao Xie <[email protected]>
>>> Cc: Goffredo Baroncelli <[email protected]>
>>> Cc: David Sterba <[email protected]>
>>>
>>> ---
>>> fs/btrfs/ioctl.c | 21 +++++++++++++++++++++
>>> fs/btrfs/ioctl.h | 2 ++
>>> 2 files changed, 23 insertions(+)
>>>
>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>>> index 8fcf9a5..ef2f55a 100644
>>> --- a/fs/btrfs/ioctl.c
>>> +++ b/fs/btrfs/ioctl.c
>>> @@ -3699,6 +3699,25 @@ out:
>>> return ret;
>>> }
>>>
>>
>> May be that it was already discussed, and I am missing something, but if
>> we check the label length we should terminate the string with a zero in
>> case this is too long...
>>
>> However this is a minor bug, please push this patch forward..
> I don't think so.
> Why we need to terminate the string with a zero?
> We have already truncated the label string up to maximum 255 bytes if it
> was too long.
>
> Consider the normal conditions, i.e. the label string is less than 256,
> we just copy it back to the user without a terminated NUL.
Sorry I don't understand the reason to terminate the string up to 255
chars without adding a zero. Or we copy all the buffer (BTRFS_LABEL_SIZE
characters without furthers checks) or we copy BTRFS_LABEL_SIZE-1
characters, adding a zero at the end.
>>
>>
>>> +static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
>>> +{
>>> + struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
>>> + const char *label = root->fs_info->super_copy->label;
>>> + size_t len = strnlen(label, BTRFS_LABEL_SIZE);
>>> + int ret;
>> + int label_is_too_long = 0;
> bool label_is_too_long = false;
>>> +
>>> + if (len == BTRFS_LABEL_SIZE) {
>>> + pr_warn("btrfs: label is too long, return the first %zu
>>> bytes\n",
>>> + --len);
>>
>> + label_is_too_long = 1;
> label_is_too_long = true;
>>> + }
>>> +
>>> + mutex_lock(&root->fs_info->volume_mutex);
>>> + ret = copy_to_user(arg, label, len);
>> + if (!ret && label_is_too_long)
>> + ret = copy_to_user(arg+BTRFS_LABEL_SIZE, "", 1);
> Hmm? ret = copy_to_user(arg + len, "", 1);
>
My idea was to put a zero at the end of the string, but I did a mistake
with the cut&paste.. sorry :-)
>>> + mutex_unlock(&root->fs_info->volume_mutex);
> If you or anyone has objection to this patch, please just post yours, I
> won't follow it up again.
Sorry I don't want to bother anybody, I know that reviewing a patch nine
times is a very havvy work. I (and I think more other peoples) really
appreciate your efforts.
BR
G.Baroncelli
>>> +
>>> + return ret ? -EFAULT : 0;
>>> +}
>>> +
>>> long btrfs_ioctl(struct file *file, unsigned int
>>> cmd, unsigned long arg)
>>> {
>>> @@ -3797,6 +3816,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>> return btrfs_ioctl_qgroup_create(root, argp);
>>> case BTRFS_IOC_QGROUP_LIMIT:
>>> return btrfs_ioctl_qgroup_limit(root, argp);
>>> + case BTRFS_IOC_GET_FSLABEL:
>>> + return btrfs_ioctl_get_fslabel(file, argp);
>>> }
>>>
>>> return -ENOTTY;
>>> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
>>> index 731e287..5b2cbef 100644
>>> --- a/fs/btrfs/ioctl.h
>>> +++ b/fs/btrfs/ioctl.h
>>> @@ -451,6 +451,8 @@ struct btrfs_ioctl_send_args {
>>> struct btrfs_ioctl_qgroup_create_args)
>>> #define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
>>> struct btrfs_ioctl_qgroup_limit_args)
>>> +#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
>>> + char[BTRFS_LABEL_SIZE])
>>> #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
>>> struct btrfs_ioctl_get_dev_stats)
>>> #endif
>>
>>
>
>
--
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