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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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