linux-kernel - Re: [PATCH] dcache: fix d_splice

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Message-ID: <20140117180441.GB26636@fieldses.org>
Date:	Fri, 17 Jan 2014 13:04:41 -0500
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Steven Whitehouse <swhiteho@...hat.com>
Cc:	Bob Peterson <rpeterso@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, Miklos Szeredi <mszeredi@...e.cz>
Subject: Re: [PATCH] dcache: fix d_splice_alias handling of aliases

On Fri, Jan 17, 2014 at 10:04:30AM +0000, Steven Whitehouse wrote:
> Hi,
> 
> On Thu, 2014-01-16 at 13:51 -0500, J. Bruce Fields wrote:
> > On Thu, Jan 16, 2014 at 11:54:07AM -0500, Bob Peterson wrote:
> > > ----- Original Message -----
> > > | Something like this?
> > > (snip)
> > > | @@ -779,6 +782,11 @@ static struct dentry *__gfs2_lookup(struct inode *dir,
> > > | struct dentry *dentry,
> > > |  	}
> > > |  
> > > |  	d = d_splice_alias(inode, dentry);
> > > | +	if (IS_ERR(d)) {
> > > | +		iput(inode);
> > > | +		gfs2_glock_dq_uninit(&gh);
> > > | +		return ERR_PTR(error);
> > > 
> > > ---------------------------------^
> > > Shouldn't that be ERR_PTR(d)?
> > 
> > Oops, yeah--well, actually just "d" I guess.
> > 
> > This is what I've got for what it's worth.
> > 
> > --b.
> > 
> 
> I think the patch looks ok to me. Did you give it a spin to test it?

Sure, just
	mkfs.gfs2 -p lock_nolock /dev/vdb
	mount /dev/vdb /mnt/
	cd cthon
	NFSTESTDIR=/mnt/TMP ./runtests -a -f

Which doesn't test much of anything (we'd need to inject artificial
errors for now to test the error paths), but at least it doesn't blow up
in some obvious way....

> If so then I will put it in the GFS2 -nmw tree,

Thanks!

--b.

> 
> Steve.
> 
> > commit 6fba5295019b52a03d76c9e9570952466051a7a6
> > Author: J. Bruce Fields <bfields@...hat.com>
> > Date:   Thu Jan 16 11:44:53 2014 -0500
> > 
> >     gfs2: revert "GFS2: d_splice_alias() can't return error"
> >     
> >     0d0d110720d7960b77c03c9f2597faaff4b484ae asserts that "d_splice_alias()
> >     can't return error unless it was given an IS_ERR(inode)".
> >     
> >     That was true of the implementation of d_splice_alias, but this is
> >     really a problem with d_splice_alias: at a minimum it should be able to
> >     return -ELOOP in the case where inserting the given dentry would cause a
> >     directory loop.
> >     
> >     Signed-off-by: J. Bruce Fields <bfields@...hat.com>
> > 
> > diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
> > index 7119504..3f44902 100644
> > --- a/fs/gfs2/inode.c
> > +++ b/fs/gfs2/inode.c
> > @@ -585,6 +585,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
> >  	error = PTR_ERR(inode);
> >  	if (!IS_ERR(inode)) {
> >  		d = d_splice_alias(inode, dentry);
> > +		error = PTR_ERR(d);
> > +		if (IS_ERR(d))
> > +			goto fail_gunlock;
> >  		error = 0;
> >  		if (file) {
> >  			if (S_ISREG(inode->i_mode)) {
> > @@ -779,6 +782,11 @@ static struct dentry *__gfs2_lookup(struct inode *dir, struct dentry *dentry,
> >  	}
> >  
> >  	d = d_splice_alias(inode, dentry);
> > +	if (IS_ERR(d)) {
> > +		iput(inode);
> > +		gfs2_glock_dq_uninit(&gh);
> > +		return d;
> > +	}
> >  	if (file && S_ISREG(inode->i_mode))
> >  		error = finish_open(file, dentry, gfs2_open_common, opened);
> >  
> 
> 
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