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Subject[patch 2/7] vfs: mountinfo: add seq_file_root()
From: Miklos Szeredi <mszeredi@suse.cz>

Add a new function:

seq_file_root()

This is similar to seq_path(), but calculates the path relative to the
given root, instead of current->fs->root. If the path was unreachable
from root, then modify the root parameter to reflect this.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/dcache.c | 24 ++++++++++++++++--------
fs/seq_file.c | 30 ++++++++++++++++++++++++++++++
include/linux/dcache.h | 1 +
include/linux/seq_file.h | 2 ++
4 files changed, 49 insertions(+), 8 deletions(-)
Index: vfs-2.6/fs/dcache.c
===================================================================
--- vfs-2.6.orig/fs/dcache.c 2008-03-26 21:37:35.000000000 +0100
+++ vfs-2.6/fs/dcache.c 2008-03-26 21:37:38.000000000 +0100
@@ -1759,10 +1759,8 @@ static int prepend(char **buffer, int *b

/**
* d_path - return the path of a dentry
- * @dentry: dentry to report
- * @vfsmnt: vfsmnt to which the dentry belongs
- * @root: root dentry
- * @rootmnt: vfsmnt to which the root dentry belongs
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry (may be modified by this function)
* @buffer: buffer to return value in
* @buflen: buffer length
*
@@ -1772,10 +1770,15 @@ static int prepend(char **buffer, int *b
* Returns the buffer or an error code if the path was too long.
*
* "buflen" should be positive. Caller holds the dcache_lock.
+ *
+ * If path is not reachable from the supplied root, then the value of
+ * root is changed (without modifying refcounts).
*/
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
- struct path *root, char *buffer, int buflen)
+char *__d_path(const struct path *path, struct path *root,
+ char *buffer, int buflen)
{
+ struct dentry *dentry = path->dentry;
+ struct vfsmount *vfsmnt = path->mnt;
char * end = buffer+buflen;
char * retval;

@@ -1824,6 +1827,8 @@ global_root:
if (prepend(&retval, &buflen, dentry->d_name.name,
dentry->d_name.len) != 0)
goto Elong;
+ root->mnt = vfsmnt;
+ root->dentry = dentry;
return retval;
Elong:
return ERR_PTR(-ENAMETOOLONG);
@@ -1846,6 +1851,7 @@ char *d_path(struct path *path, char *bu
{
char *res;
struct path root;
+ struct path tmp;

/*
* We have various synthetic filesystems that never get mounted. On
@@ -1862,7 +1868,8 @@ char *d_path(struct path *path, char *bu
path_get(&root);
read_unlock(&current->fs->lock);
spin_lock(&dcache_lock);
- res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
+ tmp = root;
+ res = __d_path(path, &tmp, buf, buflen);
spin_unlock(&dcache_lock);
path_put(&root);
return res;
@@ -1970,9 +1977,10 @@ asmlinkage long sys_getcwd(char __user *
spin_lock(&dcache_lock);
if (pwd.dentry->d_parent == pwd.dentry || !d_unhashed(pwd.dentry)) {
unsigned long len;
+ struct path tmp = root;
char * cwd;

- cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE);
+ cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
spin_unlock(&dcache_lock);

error = PTR_ERR(cwd);
Index: vfs-2.6/fs/seq_file.c
===================================================================
--- vfs-2.6.orig/fs/seq_file.c 2008-03-26 21:37:35.000000000 +0100
+++ vfs-2.6/fs/seq_file.c 2008-03-26 21:37:38.000000000 +0100
@@ -385,6 +385,36 @@ int seq_path(struct seq_file *m, struct
EXPORT_SYMBOL(seq_path);

/*
+ * Same as seq_path, but relative to supplied root.
+ *
+ * root may be changed, see __d_path().
+ */
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+ char *esc)
+{
+ int err = -ENAMETOOLONG;
+ if (m->count < m->size) {
+ char *s = m->buf + m->count;
+ char *p;
+
+ spin_lock(&dcache_lock);
+ p = __d_path(path, root, s, m->size - m->count);
+ spin_unlock(&dcache_lock);
+ err = PTR_ERR(p);
+ if (!IS_ERR(p)) {
+ s = mangle_path(s, p, esc);
+ if (s) {
+ p = m->buf + m->count;
+ m->count = s - m->buf;
+ return 0;
+ }
+ }
+ }
+ m->count = m->size;
+ return err;
+}
+
+/*
* returns the path of the 'dentry' from the root of its filesystem.
*/
int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
Index: vfs-2.6/include/linux/dcache.h
===================================================================
--- vfs-2.6.orig/include/linux/dcache.h 2008-03-26 21:37:35.000000000 +0100
+++ vfs-2.6/include/linux/dcache.h 2008-03-26 21:37:38.000000000 +0100
@@ -301,6 +301,7 @@ extern int d_validate(struct dentry *, s
*/
extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);

+extern char *__d_path(const struct path *path, struct path *root, char *, int);
extern char *d_path(struct path *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);

Index: vfs-2.6/include/linux/seq_file.h
===================================================================
--- vfs-2.6.orig/include/linux/seq_file.h 2008-03-26 21:37:35.000000000 +0100
+++ vfs-2.6/include/linux/seq_file.h 2008-03-26 21:37:38.000000000 +0100
@@ -44,6 +44,8 @@ int seq_printf(struct seq_file *, const

int seq_path(struct seq_file *, struct path *, char *);
int seq_dentry(struct seq_file *, struct dentry *, char *);
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+ char *esc);

int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
int single_release(struct inode *, struct file *);
--


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