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The use of kmap_atomic() is being deprecated in favor of kmap_local_page()[1]. The main difference between atomic and local mappings is that local mappings doesn't disable page faults or preemption (the preemption is disabled for !PREEMPT_RT case, otherwise it only disables migration). With kmap_local_page(), we can avoid the often unwanted side effect of unnecessary page faults or preemption disables. In drm/i915/gem/i915_gem_shmem.c, the function shmem_pwrite() need to disable pagefault to eliminate the potential recursion fault[2]. But here __copy_from_user_inatomic() doesn't need to disable preemption and local mapping is valid for sched in/out. So it can use kmap_local_page() / kunmap_local() with pagefault_disable() / pagefault_enable() to replace atomic mapping. [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com [2]: https://patchwork.freedesktop.org/patch/295840/ Suggested-by: Ira Weiny <ira.weiny@intel.com> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by: Zhao Liu <zhao1.liu@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20231203132947.2328805-4-zhao1.liu@linux.intel.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.