Since Paulo pointed out a problem with v4 of this patch, an obvious
question is Dan's patch "independent enough" to take or would it make
the v5 of your patch harder. Let me know when there is a v5 of the
patch so we can do more testing and review
On Mon, Aug 18, 2025 at 8:30 AM Wang Zhaolong
<wangzhaolong@xxxxxxxxxxxxxxx> wrote:
Hi Steve, Paulo, and Dan,
Thank you very much for your attention to this patch.
The NULL pointer issue has already been addressed in the V4
version of the patch. I have considered submitting a V5 version
of the patch, but I have not yet decided whether to proceed with it.
While further analyzing the code, I discovered the following
potential issues in the implementation of `cifs_tree_connect()` in
`dfs.c`, which calls `cifs_get_dfs_tcon_super()`:
1. `cifs_get_dfs_tcon_super()` only returns a single superblock reference.
Using this superblock, it retrieves the associated `cifs_sb`. However,
a single tcon is supposed to be associated with multiple `cifs_sb`
instances. I am unsure whether there is a mechanism that guarantees a
DFS tcon (where `tcon->origin_fullpath` is non-NULL) has exactly one
associated `cifs_sb`. My current patch series only retrieves the first
`cifs_sb` that satisfies the condition, which may not be sufficient.
2. The only purpose of retrieving the `cifs_sb` is to update the `prepath`
field of the `cifs_sb` in `tree_connect_dfs_target()` by calling
`cifs_update_super_prepath()`. No other information from the VFS-layer
superblock is used. However, retrieving the superblock is also meant to
pin it in memory to prevent it from being released. Therefore, I am
considering whether to simplify the process of updating the prepath.
If I decide to submit a V5 version of the patch, I will need to fully investigate:
1. Whether a DFS tcon can be associated with multiple `cifs_sb` instances.
2. If multiple `cifs_sb` instances are associated with a DFS tcon, whether
the `prepath` field of all associated `cifs_sb` instances needs to be
updated.
Only after thoroughly understanding these two points can I come up with a
better implementation for the V5 patch.
Resolving these questions will take some time. If anyone can provide
guidance or assistance, I would greatly appreciate it.
Best regards,
Wang Zhaolong
Wang Zhaolong
