[Devel] [PATCH 2/2] fs/fuse kio_pcs: check fuse_conn args

[Kirill Tkhai]

On 17.05.2018 14:31, Pavel Butsykin wrote:
> On 17.05.2018 13:05, Kirill Tkhai wrote:
>> Hi, Pasha,
>>
>> On 17.05.2018 12:40, Pavel Butsykin wrote:
>>> Allow initialization of kdirect only for vstorage/pstorage.
>>>
>>> Signed-off-by: Pavel Butsykin <pbutsykin at virtuozzo.com>
>>> ---
>>>   drivers/block/ploop/dev.c          |  4 ----
>>>   fs/fuse/kio/pcs/pcs_fuse_kdirect.c | 23 +++++++++++++++++------
>>>   include/linux/fs.h                 |  5 +++++
>>>   3 files changed, 22 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
>>> index 0e72656ec8f9..c6094144c7a5 100644
>>> --- a/drivers/block/ploop/dev.c
>>> +++ b/drivers/block/ploop/dev.c
>>> @@ -3880,10 +3880,6 @@ static int ploop_truncate(struct ploop_device * plo, unsigned long arg)
>>>       return err;
>>>   }
>>>   -#define IS_PSTORAGE(sb) (sb->s_magic == FUSE_SUPER_MAGIC && \
>>> -             (!strcmp(sb->s_subtype, "pstorage") || \
>>> -              !strcmp(sb->s_subtype, "vstorage")))
>>> -
>>>   static int ploop_bd_full(struct backing_dev_info *bdi, long long nr, int root)
>>>   {
>>>       struct ploop_device *plo      = bdi->congested_data;
>>> diff --git a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>>> index b8503d55e246..4b9c4a304571 100644
>>> --- a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>>> +++ b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>>> @@ -144,13 +144,24 @@ void kpcs_conn_abort(struct fuse_conn *fc)
>>>   }
>>>     static int kpcs_probe(struct fuse_conn *fc, char *name)
>>> -
>>>   {
>>> -    printk("%s TODO IMPLEMENT check fuse_conn args here!\n", __FUNCTION__);
>>> -    if (!strncmp(name, kio_pcs_ops.name, FUSE_KIO_NAME))
>>> -        return 1;
>>> +    if (strncmp(name, kio_pcs_ops.name, FUSE_KIO_NAME)) {
>>> +        printk(KERN_ERR "FUSE: kio_pcs: invalid kio_ops name: %s\n", name);
>>
>> Despite there was printk() without error level modifier (which is not correct),
>> and printk(KERN_ERR) is better, let's follow the modern Linux kernel style,
>> which anyway will be requested in case of submitting patches to mainstream.
>> pr_err() is more likely to use for such the printing (see the rest of pr_* in printk.h).
>>
> 
> ok, thanks.
> 
>>> +        return 0;
>>> +    }
>>>   -    return 0;
>>> +    if (!(fc->flags & FUSE_KDIRECT_IO)) {
>>> +        printk(KERN_ERR "FUSE: kio_pcs: kdirect is not enabled\n");
>>> +        return 0;
>>> +    }
>>
>> I don't think this is needed, since we already check for this bit in fuse_fill_super()
>> before call of fuse_kio_get(). But I'm not insist on this.
>>
> 
> And what is the meaning of this check:
> "!strncmp(name, kio_pcs_ops.name, FUSE_KIO_NAME)" ?

FUSE_KIO_NAME looks like a define of string, but it's a size,
and it was confusing for me.

Possible, we can drop this too. Less code is better for the attention.

> We also already have this check. I assumed this can protect against
> possible mistakes in the future.

I think, we fastly find the root cause in case of something is wrong
on mount. Duplications confuse... But I'm not insist on this.

>>> +
>>> +    if (!IS_PSTORAGE(fc->sb)) {
>>> +        printk(KERN_ERR "FUSE: kio_pcs: kdirect is only available for"
>>> +                        "pstorage/vstorage fuse mount\n");
>>> +        return 0;
>>> +    }
>>> +
>>> +    return 1;
>>>   }
>>>     @@ -1202,7 +1213,7 @@ err:
>>>   static struct fuse_kio_ops kio_pcs_ops = {
>>>       .name        = "pcs",
>>>       .owner        = THIS_MODULE,
>>> -    .probe        = kpcs_probe, /*TODO: check sb->dev name */
>>> +    .probe        = kpcs_probe,
>>>         .conn_init    = kpcs_conn_init,
>>>       .conn_fini    = kpcs_conn_fini,
>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>> index a1dc3521f979..21770550b6c1 100644
>>> --- a/include/linux/fs.h
>>> +++ b/include/linux/fs.h
>>> @@ -1713,6 +1713,11 @@ struct super_block {
>>>       struct list_lru        s_inode_lru ____cacheline_aligned_in_smp;
>>>   };
>>>   +#define IS_PSTORAGE(sb) ((sb)->s_magic == FUSE_SUPER_MAGIC && \
>>> +             (sb)->s_subtype && \
>>> +             (!strcmp((sb)->s_subtype, "pstorage") || \
>>> +              !strcmp((sb)->s_subtype, "vstorage")))
>>> +
>>>   extern const unsigned super_block_wrapper_version;
>>>   struct super_block_wrapper {
>>>       struct super_block sb;
>>>
>>
>> Thanks,
>> Kirill
>>