5bd3c1c1bc
[ Upstream commit 9fb0db40513e27537fde63287aea920b60557a69 ]
Avoid getting DFS referral from an exclusive lock in
cache_refresh_path() because the tcon IPC used for getting the
referral could be disconnected and thus causing a deadlock as shown
below:
task A task B
====== ======
cifs_demultiplex_thread() dfs_cache_find()
cifs_handle_standard() cache_refresh_path()
reconnect_dfs_server() down_write()
dfs_cache_noreq_find() get_dfs_referral()
down_read() <- deadlock smb2_get_dfs_refer()
SMB2_ioctl()
cifs_send_recv()
compound_send_recv()
wait_for_response()
where task A cannot wake up task B because it is blocked on
down_read() due to the exclusive lock held in cache_refresh_path() and
therefore not being able to make progress.
Fixes: c9f711039905 ("cifs: keep referral server sessions alive")
Reviewed-by: Aurélien Aptel <aurelien.aptel@gmail.com>
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.