2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
commit cde93be45a8a90d8c264c776fab63487b5038a65 upstream.
A rename can result in a dentry that by walking up d_parent
will never reach it's mnt_root. For lack of a better term
I call this an escaped path.
prepend_path is called by four different functions __d_path,
d_absolute_path, d_path, and getcwd.
__d_path only wants to see paths are connected to the root it passes
in. So __d_path needs prepend_path to return an error.
d_absolute_path similarly wants to see paths that are connected to
some root. Escaped paths are not connected to any mnt_root so
d_absolute_path needs prepend_path to return an error greater
than 1. So escaped paths will be treated like paths on lazily
unmounted mounts.
getcwd needs to prepend "(unreachable)" so getcwd also needs
prepend_path to return an error.
d_path is the interesting hold out. d_path just wants to print
something, and does not care about the weird cases. Which raises
the question what should be printed?
Given that <escaped_path>/<anything> should result in -ENOENT I
believe it is desirable for escaped paths to be printed as empty
paths. As there are not really any meaninful path components when
considered from the perspective of a mount tree.
So tweak prepend_path to return an empty path with an new error
code of 3 when it encounters an escaped path.
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[bwh: For 2.6.32, implement the "(unreachable)" string in __d_path()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
fs/dcache.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 44c0aea..07c4472 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1910,7 +1910,7 @@ char *__d_path(const struct path *path, struct path *root,
struct dentry *dentry = path->dentry;
struct vfsmount *vfsmnt = path->mnt;
char *end = buffer + buflen;
- char *retval;
+ char *retval, *tail;
spin_lock(&vfsmount_lock);
prepend(&end, &buflen, "\0", 1);
@@ -1923,6 +1923,7 @@ char *__d_path(const struct path *path, struct path *root,
/* Get '/' right */
retval = end-1;
*retval = '/';
+ tail = end;
for (;;) {
struct dentry * parent;
@@ -1930,6 +1931,14 @@ char *__d_path(const struct path *path, struct path *root,
if (dentry == root->dentry && vfsmnt == root->mnt)
break;
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+ /* Escaped? */
+ if (dentry != vfsmnt->mnt_root) {
+ buflen += (tail - end);
+ end = tail;
+ prepend(&end, &buflen, "(unreachable)/", 14);
+ retval = end;
+ goto out;
+ }
/* Global root? */
if (vfsmnt->mnt_parent == vfsmnt) {
goto global_root;
--
1.7.12.2.21.g234cd45.dirty
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