Re: [PATCH] ceph: make the lost+found dir accessible by kernel client

From: Xiubo Li <xiubli@redhat.com>
To: Jeff Layton <jlayton@kernel.org>
Cc: idryomov@gmail.com, pdonnell@redhat.com, ukernel@gmail.com,
	ceph-devel@vger.kernel.org
Subject: Re: [PATCH] ceph: make the lost+found dir accessible by kernel client
Date: Tue, 20 Apr 2021 10:02:07 +0800	[thread overview]
Message-ID: <294a5c31-f40c-b424-0497-6737c5cd583d@redhat.com> (raw)
In-Reply-To: <02cc34a899aab7169ecfdc9b15bb5dcb3d19edd8.camel@kernel.org>

On 2021/4/20 0:09, Jeff Layton wrote:
> On Mon, 2021-04-19 at 10:32 +0800, xiubli@redhat.com wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> Inode number 0x4 is reserved for the lost+found dir, and the app
>> or test app need to access it.
>>
>> URL: https://tracker.ceph.com/issues/50216
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   fs/ceph/super.h              | 3 ++-
>>   include/linux/ceph/ceph_fs.h | 7 ++++---
>>   2 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>> index 4808a1458c9b..0f38e6183ff0 100644
>> --- a/fs/ceph/super.h
>> +++ b/fs/ceph/super.h
>> @@ -542,7 +542,8 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
>>   
>>
>>
>>
>>   static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
>>   {
>> -	if (vino.ino < CEPH_INO_SYSTEM_BASE && vino.ino != CEPH_INO_ROOT) {
>> +	if (vino.ino < CEPH_INO_SYSTEM_BASE && vino.ino != CEPH_INO_ROOT &&
>> +	    vino.ino != CEPH_INO_LOST_AND_FOUND ) {
>>   		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
>>   		return true;
>>   	}
>> diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
>> index e41a811026f6..57e5bd63fb7a 100644
>> --- a/include/linux/ceph/ceph_fs.h
>> +++ b/include/linux/ceph/ceph_fs.h
>> @@ -27,9 +27,10 @@
>>   #define CEPH_MONC_PROTOCOL   15 /* server/client */
>>   
>>
>>
>>
>>   
>>
>>
>>
>> -#define CEPH_INO_ROOT   1
>> -#define CEPH_INO_CEPH   2       /* hidden .ceph dir */
>> -#define CEPH_INO_DOTDOT 3	/* used by ceph fuse for parent (..) */

Hi Jeff,

Please fix the "CEPH_INO_DOTDOT" when you folding this patch. The inode 
number 3 is not _DOTDOT any more. This was introduced by an very old 
commit(dd6f5e105d85e) but I couldn't find the related change about this 
in ceph code.

It should be:

#define CEPH_INO_GLOBAL_SNAPREALM 3

>> +#define CEPH_INO_ROOT           1
>> +#define CEPH_INO_CEPH           2 /* hidden .ceph dir */
>> +#define CEPH_INO_DOTDOT         3 /* used by ceph fuse for parent (..) */
>> +#define CEPH_INO_LOST_AND_FOUND 4 /* lost+found dir */
>>   
>>
>>
>>
>>   /* arbitrary limit on max # of monitors (cluster of 3 is typical) */
>>   #define CEPH_MAX_MON   31
> Thanks Xiubo,
>
> For some background, apparently cephfs-data-scan can create this
> directory, and the clients do need access to it. I'll fold this into the
> original patch that makes these inodes inaccessible (ceph: don't allow
> access to MDS-private inodes).
>
> Cheers!