linux-kernel - Re: [PATCH v2] hfsplus: remove mutex_lock check in hfsplus_free

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Message-ID: <20250529183643.GM2023217@ZenIV>
Date: Thu, 29 May 2025 19:36:43 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>
Cc: "frank.li@...o.com" <frank.li@...o.com>,
	"glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>,
	"slava@...eyko.com" <slava@...eyko.com>,
	"ernesto.mnd.fernandez@...il.com" <ernesto.mnd.fernandez@...il.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"syzbot+8c0bc9f818702ff75b76@...kaller.appspotmail.com" <syzbot+8c0bc9f818702ff75b76@...kaller.appspotmail.com>
Subject: Re: [PATCH v2] hfsplus: remove mutex_lock check in
 hfsplus_free_extents

On Thu, May 29, 2025 at 06:34:43PM +0000, Viacheslav Dubeyko wrote:
> > diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
> > index a6d61685ae79..b1699b3c246a 100644
> > --- a/fs/hfsplus/extents.c
> > +++ b/fs/hfsplus/extents.c
> > @@ -342,9 +342,6 @@ static int hfsplus_free_extents(struct super_block *sb,
> >  	int i;
> >  	int err = 0;
> >  
> > -	/* Mapping the allocation file may lock the extent tree */
> > -	WARN_ON(mutex_is_locked(&HFSPLUS_SB(sb)->ext_tree->tree_lock));
> > -
> 
> Makes sense to me. Looks good.
> 
> But I really like your mentioning of reproducing the issue in generic/013 and
> really nice analysis of the issue there. Sadly, we haven't it in the comment. :)

Umm...  *Is* that thing safe to call without that lock?