linux-kernel - Re: [PATCH v2] Fix i_mutex handling in nfsd readdir

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Message-ID: <9180.1240468823@jrobl>
Date:	Thu, 23 Apr 2009 15:40:23 +0900
From:	hooanon05@...oo.co.jp
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Al Viro <viro@...IV.linux.org.uk>, hch@...radead.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2] Fix i_mutex handling in nfsd readdir 


"J. Bruce Fields":
> > Isn't it better to test it BEFORE fh_compose()?
	:::
> Yes, I think you're right.

Then here you are.

J. R. Okajima

----------------------------------------------------------------------

commit c98c6c4a207d602bd9498ea5f1d2993a00e98445
Author: J. R. Okajima <hooanon05@...oo.co.jp>
Date:   Thu Apr 23 15:38:43 2009 +0900

    NFSD: test d_inode before fh_compose()
    
    After 2f9092e1020246168b1309b35e085ecd7ff9ff72 "Fix i_mutex vs. readdir
    handling in nfsd" (and 14f7dd63 "Copy XFS readdir hack into nfsd code"),
    an entry may be removed between the first mutex_unlock and the second
    mutex_lock. In this case, lookup_one_len() in compose_entry_fh() will
    return a negative dentry.
    It is better to test inode (positive/negative) BEFORE fh_compose().
    
    Signed-off-by: J. R. Okajima <hooanon05@...oo.co.jp>

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 17d0dd9..1b5543b 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -851,8 +851,8 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
 	if (IS_ERR(dchild))
 		return 1;
 	if (d_mountpoint(dchild) ||
-	    fh_compose(fhp, exp, dchild, &cd->fh) != 0 ||
-	    !dchild->d_inode)
+	    !dchild->d_inode ||
+	    fh_compose(fhp, exp, dchild, &cd->fh) != 0)
 		rv = 1;
 	dput(dchild);
 	return rv;
--
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