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[ Upstream commit9fb0db4051] 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:c9f7110399("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.