linux-kernel - Re: [PATCH] fs/dcache: prevent repeated locking

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Message-ID: <Ya/cAOtx/EoAgWOi@casper.infradead.org>
Date:   Tue, 7 Dec 2021 22:11:12 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     cgel.zte@...il.com, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lv Ruyi <lv.ruyi@....com.cn>, Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] fs/dcache: prevent repeated locking

On Tue, Dec 07, 2021 at 01:25:18PM -0800, Eric Biggers wrote:
> On Tue, Dec 07, 2021 at 01:17:41PM +0000, Matthew Wilcox wrote:
> > On Tue, Dec 07, 2021 at 10:16:46AM +0000, cgel.zte@...il.com wrote:
> > > From: Lv Ruyi <lv.ruyi@....com.cn>
> > > 
> > > Move the spin_lock above the restart to prevent to lock twice 
> > > when the code goto restart.
> > 
> > This is madness.
> > 
> > void d_prune_aliases(struct inode *inode)
> >         spin_lock(&inode->i_lock);
> >                         if (likely(!dentry->d_lockref.count)) {
> >                                 __dentry_kill(dentry);
> >                                 goto restart;
> > ...
> > static void __dentry_kill(struct dentry *dentry)
> >         if (dentry->d_inode)
> >                 dentry_unlink_inode(dentry);
> > ...
> > static void dentry_unlink_inode(struct dentry * dentry)
> >         spin_unlock(&inode->i_lock);
> > 
> > Did you even test this patch?
> 
> This same wrong patch has been sent several times before.  I think it's fair to
> say that this code could use a comment, e.g.:
> 
> 	/* i_lock was dropped */
> 	goto restart;

Not sure that'll do much good.  It seems to be fools running some script
that they haven't the wit to understand.