linux-kernel - Re: Regression with initramfs and nfsroot (appears to be in the dcache)

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Message-ID: <20121129213316.GU4939@ZenIV.linux.org.uk>
Date:	Thu, 29 Nov 2012 21:33:16 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Patrick McLean <patrickm@...kai.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Regression with initramfs and nfsroot (appears to be in the
 dcache)

On Thu, Nov 29, 2012 at 11:16:59AM -0800, Patrick McLean wrote:
> With 3.6-rc1 and up, when using a (dracut) initramfs with a read-only
> nfs root, all accesses to /proc. /sys and /dev return EBUSY.

See "[PATCH] Revert "__d_unalias() should refuse to move mountpoints"
thread.  If you have a convenient reproducer, could you check if
the fixes the breakage?  If so, we'll need to look into false negatives
from nfs_same_file() in there...

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index ce8cb92..55436f5 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -450,7 +450,10 @@ void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
 			nfs_refresh_inode(dentry->d_inode, entry->fattr);
 			goto out;
 		} else {
-			d_drop(dentry);
+			if (d_invalidate(dentry) != 0) {
+				WARN_ON(1);
+				goto out;
+			}
 			dput(dentry);
 		}
 	}
--
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