[PATCH review 16/19] mnt: Track which mounts use a dentry as root.

Eric W. Biederman ebiederm at xmission.com
Fri Apr 3 10:31:22 UTC 2015

On April 3, 2015 12:54:50 AM CDT, Al Viro <viro at ZenIV.linux.org.uk> wrote:
>On Thu, Apr 02, 2015 at 08:56:20PM -0500, Eric W. Biederman wrote:
>One general note - I'd probably put a pointer to that sucker into
>mount.  For one thing, root-preserving clone_mnt() is a fairly common
>case.  For another, searching for that thing in mnt_put_root() looks
>wrong.  Matter of taste, but...
>Another thing is that IMO it's better to preallocate that thing in
>vfs_kern_mount() and free if it turns out to be unused.  Simpler
>path that way...

Those do sound like reasonable simplifications.

>> -	mnt->mnt.mnt_root = root;
>> +	err = mnt_set_root(mnt, root);
>> +	if (err) {
>> +		dput(mnt->mnt.mnt_root);
>	Unless I'm misreading your code, mnt_set_root() does *not* set it
>on failure, so what's going on here?

I will have to look when I get the code in front of me again.

>>  #define DCACHE_FALLTHRU			0x01000000 /* Fall through to lower layer
>						^^^^^^^^^^
>> +#define DCACHE_MOUNTROOT		0x01000000 /* is root of a vfsmount */
>					^^^^^^^^^^
>	Er...

Good point.  I don't think DCACHE_FALLTHRU existed when I wrote the patch and I missed this detail during the rebase.  Sigh.

I will fix it for the next round.   Hopefully DCACHE_FALLTHRU does not have implications for the rest of my changes.


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