Re: [EXT4 set 4][PATCH 1/5] i_version:64 bit inode version

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, 2007-07-11 at 15:05 +1000, Neil Brown wrote:
> It just occurred to me:
> 
>  If i_version is 64bit, then knfsd would need to be careful when
>  reading it on a 32bit host.  What are the locking rules?

How does knfsd use i_version?  I would think that if all it was doing
was to compare (i_version == previous_version), then locking wouldn't
really matter.  Well, theoretically, previous_version could be
0x100000000, and i_version could be 0x1ffffffff, knfsd checks the high
word, then ext4 updates i_version to 0x200000000, then knfsd checks the
low word, detecting no change.  How likely is this?  (I don't understand
why i_version even needs to be 64 bits in the first place.)

>  Presumably it is only updated under i_mutex protection, but having to
>  get i_mutex to read it would seem a little heavy handed.

How does knfsd protect itself from the inode changing after i_version is
checked?  Is any locking being done otherwise?

>  Should it use a seqlock like i_size?
>  Could we use the same seqlock that i_size uses, or would we need a
>  separate one?
> 
> NeilBrown

-- 
David Kleikamp
IBM Linux Technology Center

-
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux