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SCSI can call device_add_disk() several times for one request queue when a device in unbound and bound, creating new gendisk each time. This will lead to bdi being repeatedly registered and unregistered. This was not a big problem until commit165a5e22fa"block: Move bdi_unregister() to del_gendisk()" since bdi was only registered repeatedly (bdi_register() handles repeated calls fine, only we ended up leaking reference to gendisk due to overwriting bdi->owner) but unregistered only in blk_cleanup_queue() which didn't get called repeatedly. After165a5e22fawe were doing correct bdi_register() - bdi_unregister() cycles however bdi_unregister() is not prepared for it. So make sure bdi_unregister() cleans up bdi in such a way that it is prepared for a possible following bdi_register() call. An easy way to provoke this behavior is to enable CONFIG_DEBUG_TEST_DRIVER_REMOVE and use scsi_debug driver to create a scsi disk which immediately hangs without this fix. Fixes:165a5e22faSigned-off-by: Jan Kara <jack@suse.cz> Tested-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.