linux-kernel - Re: [PATCH] fs: remove useless d_unhashed() retry in d_alloc

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Message-ID: <20250214014344.329213-1-alexjlzheng@tencent.com>
Date: Fri, 14 Feb 2025 09:43:44 +0800
From: Jinliang Zheng <alexjlzheng@...il.com>
To: viro@...iv.linux.org.uk
Cc: alexjlzheng@...il.com,
	alexjlzheng@...cent.com,
	brauner@...nel.org,
	jack@...e.cz,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: remove useless d_unhashed() retry in d_alloc_parallel()

On Thu, 13 Feb 2025 13:20:06 +0000, Al Viro wrote:
> On Thu, Feb 14, 2025 at 08:21:37PM +0800, Jinliang Zheng wrote:
> > After commit 45f78b0a2743 ("fs/dcache: Move the wakeup from
> > __d_lookup_done() to the caller."), we will only wake up
> > d_wait_lookup() after adding dentry to dentry_hashtable.
> 
> Not true.  d_lookup_done() might be called without having
> *ever* hashed the sucker.
> 
> Just think for a moment - what, for example, should happen
> if ->lookup() fails?  Would you have d_alloc_parallel()
> coming during that ->lookup() (while dentry is in in-lookup
> hash) hang forever?

Haha, yes, my bad. Thanks for pointing out my mistake.

Thank you, :)
Jinliang Zheng

> 
> NAK.