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

[Al Viro <viro@ZenIV.linux.org.uk>]

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);
 		}
 	}