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All code paths which populate userptr BOs are fine with the get_pages function taking the mmap_sem lock. This allows to get rid of the pretty involved architecture with a worker being scheduled if the mmap_sem needs to be taken, but instead call GUP directly and allow it to take the lock if necessary. This simplifies the code a lot and removes the possibility of this function returning -EAGAIN, which complicates object population handling at the callers. A notable change in behavior is that we don't allow a process to populate objects with user pages from a foreign MM anymore. This would have been an invalid use before, as it breaks the assumptions made in the etnaviv kernel driver to enfore cache coherence. We now disallow this by rejecting the request to populate those objects. Well behaving userspace is unaffected by this change. Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
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.