On Sat, 20 Feb 2010 04:27:38 -0800 john.johansen@xxxxxxxxxxxxx wrote:
> From: John Johansen <john.johansen@xxxxxxxxxxxxx>
>
> When __d_path() hits a lazily unmounted mount point, it tries to prepend
> the name of the lazily unmounted dentry to the path name. It gets this wrong,
> and also overwrites the slash that separates the name from the following
> pathname component. This patch fixes that; if a process was in directory
> /foo/bar and /foo got lazily unmounted, the old result was ``foobar'' (note the
> missing slash), while the new result with this patch is ``/foo/bar''.
>
> Signed-off-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> ---
> fs/dcache.c | 27 +++++++++++++++++++++++----
> 1 files changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 953173a..df49666 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1922,11 +1922,9 @@ char *__d_path(const struct path *path, struct path *root,
> retval = end-1;
> *retval = '/';
>
> - for (;;) {
> + while(dentry != root->dentry || vfsmnt != root->mnt) {
Please put a space between the `while' and the `('.
> struct dentry * parent;
>
> - if (dentry == root->dentry && vfsmnt == root->mnt)
> - break;
> if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
> /* Global root? */
> if (vfsmnt->mnt_parent == vfsmnt) {
> @@ -1950,9 +1948,30 @@ out:
> return retval;
>
> global_root:
> - retval += 1; /* hit the slash */
> + /*
> + * We went past the (vfsmount, dentry) we were looking for and have
> + * either hit a root dentry, a lazily unmounted dentry, an
> + * unconnected dentry, or the file is on a pseudo filesystem.
> + */
> + if ((dentry->d_sb->s_flags & MS_NOUSER) ||
> + (dentry->d_name.len = 1 && *dentry->d_name.name == '/')) {
Did you really mean to assign 1 to dentry->d_name.len here? Was `=='
intended? I hope so, because modifying the dentry in d_path() would be odd.
If this was a mistake then why did the patch pass testing?
> + /*
> + * Historically, we also glue together the root dentry and
> + * remaining name for pseudo filesystems like pipefs, which
> + * have the MS_NOUSER flag set. This results in pathnames
> + * like "pipe:[439336]".
> + */
> + retval += 1; /* overwrite the slash */
> + buflen++;
> + }
> if (prepend_name(&retval, &buflen, &dentry->d_name) != 0)
> goto Elong;
> +
> + /* connect lazily unmounted mount point */
> + if (*retval != '/' && !(dentry->d_sb->s_flags & MS_NOUSER) &&
> + prepend(&retval, &buflen, "/", 1) != 0)
> + goto Elong;
> +
> root->mnt = vfsmnt;
> root->dentry = dentry;
> goto out;
--
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