Re: [PATCH] fs: Detect API misuse of i_op->lookup

[Richard Weinberger]

Am 25.01.2015 um 23:16 schrieb Al Viro:
> On Sun, Jan 25, 2015 at 10:57:40PM +0100, Richard Weinberger wrote:
>> Hunting down a refcount issue in an out-of-tree filesystem uncovered
>> that its lookup function directly returned the dentry which was passed to it.
>> Add a BUG_ON() to detect such misuse in future.
> 
> In principle, it's not a bug.  You *must* grab a reference to dentry before
> returning it, but you can very well decide to return the one you've got -
> any place where have ->lookup() return NULL has every right to become
> return dget(dentry).

Thanks for the clarification! The filesystem in question did of course
not grab a reference before returning the same dentry.

Thanks,
//richard
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