a57ad681f1
When we drop the last reference of a zone, we end up releasing it through the callback reada_zone_release(), which deletes the zone from a device's reada_zones radix tree. This tree is protected by the global readahead lock at fs_info->reada_lock. Currently all places that are sure that they are dropping the last reference on a zone, are calling kref_put() in a critical section delimited by this lock, while all other places that are sure they are not dropping the last reference, do not bother calling kref_put() while holding that lock. When working on the previous fix for hangs and use-after-frees in the readahead code, my initial attempts were different and I actually ended up having reada_zone_release() called when not holding the lock, which resulted in weird and unexpected problems. So just add an assertion there to detect such problem more quickly and make the dependency more obvious. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.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.