Re: Dcache oops

Al Viro
2016-06-03T22:37:06Z

On Fri, Jun 03, 2016 at 11:23:55PM +0100, Al Viro wrote:

> It's not that. It's explicit put_link() in do_last(), followed by
> ESTALEOPEN and subsequent misbegotten "retry the last step on ESTALEOPEN"
> looking at now-freed nd->last.name. IOW, the bug predates delayed_call
> stuff.

EOPENSTALE, that is... Oleg, could you check if the following works?

diff --git a/fs/namei.c b/fs/namei.c
index 4c4f95a..3d9511e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3166,9 +3166,7 @@ static int do_last(struct nameidata *nd,
int acc_mode = op->acc_mode;
unsigned seq;
struct inode *inode;
- struct path save_parent = { .dentry = NULL, .mnt = NULL };
struct path path;
- bool retried = false;
int error;

nd->flags &= ~LOOKUP_PARENT;
@@ -3211,7 +3209,6 @@ static int do_last(struct nameidata *nd,
return -EISDIR;
}

-retry_lookup:
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
error = mnt_want_write(nd->path.mnt);
if (!error)
@@ -3292,23 +3289,14 @@ finish_lookup:
if (unlikely(error))
return error;

- if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path.mnt) {
- path_to_nameidata(&path, nd);
- } else {
- save_parent.dentry = nd->path.dentry;
- save_parent.mnt = mntget(path.mnt);
- nd->path.dentry = path.dentry;
-
- }
+ path_to_nameidata(&path, nd);
nd->inode = inode;
nd->seq = seq;
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
finish_open:
error = complete_walk(nd);
- if (error) {
- path_put(&save_parent);
+ if (error)
return error;
- }
audit_inode(nd->name, nd->path.dentry, 0);
error = -EISDIR;
if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
@@ -3331,13 +3319,9 @@ finish_open_created:
goto out;
BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
error = vfs_open(&nd->path, file, current_cred());
- if (!error) {
- *opened |= FILE_OPENED;
- } else {
- if (error == -EOPENSTALE)
- goto stale_open;
+ if (error)
goto out;
- }
+ *opened |= FILE_OPENED;
opened:
error = open_check_o_direct(file);
if (!error)
@@ -3353,26 +3337,7 @@ out:
}
if (got_write)
mnt_drop_write(nd->path.mnt);
- path_put(&save_parent);
return error;
-
-stale_open:
- /* If no saved parent or already retried then can't retry */
- if (!save_parent.dentry || retried)
- goto out;
-
- BUG_ON(save_parent.dentry != dir);
- path_put(&nd->path);
- nd->path = save_parent;
- nd->inode = dir->d_inode;
- save_parent.mnt = NULL;
- save_parent.dentry = NULL;
- if (got_write) {
- mnt_drop_write(nd->path.mnt);
- got_write = false;
- }
- retried = true;
- goto retry_lookup;
}

static int do_tmpfile(struct nameidata *nd, unsigned flags,