d11b0b043b
Add a refcount to avoid the deadlock in on-demand read mode. The on-demand read mode will pin the corresponding cachefiles object for each anonymous fd. The cachefiles object is unpinned when the anonymous fd gets closed. When the user daemon exits and the fd of "/dev/cachefiles" device node gets closed, it will wait for all cahcefiles objects getting withdrawn. Then if there's any anonymous fd getting closed after the fd of the device node, the user daemon will hang forever, waiting for all objects getting withdrawn. To fix this, add a refcount indicating if there's any object pinned by anonymous fds. The cachefiles cache gets unbound and withdrawn when the refcount is decreased to 0. It won't change the behaviour of the original mode, in which case the cachefiles cache gets unbound and withdrawn as long as the fd of the device node gets closed. Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Link: https://lore.kernel.org/r/20220509074028.74954-4-jefflexu@linux.alibaba.com Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
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.