linux-ext4 - Re: [PATCH] ext4: Detect already used quota file early

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Date:   Thu, 15 Oct 2020 11:51:51 +0200
From:   Jan Kara <jack@...e.cz>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     Jan Kara <jack@...e.cz>, Ted Tso <tytso@....edu>,
        linux-ext4@...r.kernel.org, Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: Re: [PATCH] ext4: Detect already used quota file early

On Thu 15-10-20 01:33:24, Andreas Dilger wrote:
> On Oct 13, 2020, at 7:22 AM, Jan Kara <jack@...e.cz> wrote:
> > 
> > When we try to use file already used as a quota file again (for the same
> > or different quota type), strange things can happen. At the very least
> > lockdep annotations may be wrong but also inode flags may be wrongly set
> > / reset. When the file is used for two quota types at once we can even
> > corrupt the file and likely crash the kernel. Catch all these cases by
> > checking whether passed file is already used as quota file and bail
> > early in that case.
> > 
> > This fixes occasional generic/219 failure due to lockdep complaint.
> > 
> > Reported-by: Ritesh Harjani <riteshh@...ux.ibm.com>
> > Signed-off-by: Jan Kara <jack@...e.cz>
> 
> Patch looks OK, but a minor question/suggestion below...
> 
> Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> 
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index ea425b49b345..49b2e6be35c4 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -6042,6 +6042,11 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
> > 	/* Quotafile not on the same filesystem? */
> > 	if (path->dentry->d_sb != sb)
> > 		return -EXDEV;
> > +
> > +	/* Quota already enabled for this file? */
> > +	if (path->dentry->d_inode->i_flags & S_NOQUOTA)
> > +		return -EBUSY;
> 
> Any reason not to use IS_NOQUOTA(path->dentry->d_inode) here?  I was trying
> to see where S_NOQUOTA is set, and it seems that all of the quota code is
> using IS_NOQUOTA().

OK, right. I'll change that. Thanks for review.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR