linux-kernel - [ 48/82] nfs: Show original device name verbatim in /proc/*/mount{s,info}

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Message-Id: <20121114053940.508119031@decadent.org.uk>
Date:	Wed, 14 Nov 2012 05:40:21 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jonathan Nieder <jrnieder@...il.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 48/82] nfs: Show original device name verbatim in /proc/*/mount{s,info}

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Ben Hutchings <ben@...adent.org.uk>

commit 97a54868262da1629a3e65121e65b8e8c4419d9f upstream.

Since commit c7f404b ('vfs: new superblock methods to override
/proc/*/mount{s,info}'), nfs_path() is used to generate the mounted
device name reported back to userland.

nfs_path() always generates a trailing slash when the given dentry is
the root of an NFS mount, but userland may expect the original device
name to be returned verbatim (as it used to be).  Make this
canonicalisation optional and change the callers accordingly.

[jrnieder@...il.com: use flag instead of bool argument]
Reported-and-tested-by: Chris Hiestand <chiestand@...k.edu>
Reference: http://bugs.debian.org/669314
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Jonathan Nieder <jrnieder@...il.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
[bwh: Backported to 3.2:
 - Adjust context
 - nfs_show_devname() still takes a pointer to struct vfsmount]
---
 fs/nfs/internal.h      |    5 +++--
 fs/nfs/namespace.c     |   19 ++++++++++++++-----
 fs/nfs/nfs4namespace.c |    3 ++-
 fs/nfs/super.c         |    2 +-
 4 files changed, 20 insertions(+), 9 deletions(-)

--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -274,8 +274,9 @@ extern void nfs_sb_active(struct super_b
 extern void nfs_sb_deactive(struct super_block *sb);
 
 /* namespace.c */
+#define NFS_PATH_CANONICAL 1
 extern char *nfs_path(char **p, struct dentry *dentry,
-		      char *buffer, ssize_t buflen);
+		      char *buffer, ssize_t buflen, unsigned flags);
 extern struct vfsmount *nfs_d_automount(struct path *path);
 #ifdef CONFIG_NFS_V4
 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *);
@@ -364,7 +365,7 @@ static inline char *nfs_devname(struct d
 				char *buffer, ssize_t buflen)
 {
 	char *dummy;
-	return nfs_path(&dummy, dentry, buffer, buflen);
+	return nfs_path(&dummy, dentry, buffer, buflen, NFS_PATH_CANONICAL);
 }
 
 /*
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -37,6 +37,7 @@ static struct vfsmount *nfs_do_submount(
  * @dentry - pointer to dentry
  * @buffer - result buffer
  * @buflen - length of buffer
+ * @flags - options (see below)
  *
  * Helper function for constructing the server pathname
  * by arbitrary hashed dentry.
@@ -44,8 +45,14 @@ static struct vfsmount *nfs_do_submount(
  * This is mainly for use in figuring out the path on the
  * server side when automounting on top of an existing partition
  * and in generating /proc/mounts and friends.
+ *
+ * Supported flags:
+ * NFS_PATH_CANONICAL: ensure there is exactly one slash after
+ *		       the original device (export) name
+ *		       (if unset, the original name is returned verbatim)
  */
-char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
+char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
+	       unsigned flags)
 {
 	char *end;
 	int namelen;
@@ -78,7 +85,7 @@ rename_retry:
 		rcu_read_unlock();
 		goto rename_retry;
 	}
-	if (*end != '/') {
+	if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
 		if (--buflen < 0) {
 			spin_unlock(&dentry->d_lock);
 			rcu_read_unlock();
@@ -95,9 +102,11 @@ rename_retry:
 		return end;
 	}
 	namelen = strlen(base);
-	/* Strip off excess slashes in base string */
-	while (namelen > 0 && base[namelen - 1] == '/')
-		namelen--;
+	if (flags & NFS_PATH_CANONICAL) {
+		/* Strip off excess slashes in base string */
+		while (namelen > 0 && base[namelen - 1] == '/')
+			namelen--;
+	}
 	buflen -= namelen;
 	if (buflen < 0) {
 		spin_unlock(&dentry->d_lock);
--- a/fs/nfs/nfs4namespace.c
+++ b/fs/nfs/nfs4namespace.c
@@ -57,7 +57,8 @@ Elong:
 static char *nfs4_path(struct dentry *dentry, char *buffer, ssize_t buflen)
 {
 	char *limit;
-	char *path = nfs_path(&limit, dentry, buffer, buflen);
+	char *path = nfs_path(&limit, dentry, buffer, buflen,
+			      NFS_PATH_CANONICAL);
 	if (!IS_ERR(path)) {
 		char *colon = strchr(path, ':');
 		if (colon && colon < limit)
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -768,7 +768,7 @@ static int nfs_show_devname(struct seq_f
 	int err = 0;
 	if (!page)
 		return -ENOMEM;
-	devname = nfs_path(&dummy, mnt->mnt_root, page, PAGE_SIZE);
+	devname = nfs_path(&dummy, mnt->mnt_root, page, PAGE_SIZE, 0);
 	if (IS_ERR(devname))
 		err = PTR_ERR(devname);
 	else


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