mm/ksm: use kmap_local_page() in calc_checksum()
kmap_atomic() has been deprecated in favor of kmap_local_page(). Therefore, replace kmap_atomic() with kmap_local_page() in calc_checksum(). kmap_atomic() is implemented like a kmap_local_page() which also disables page-faults and preemption (the latter only in !PREEMPT_RT kernels). The kernel virtual addresses returned by these two API are only valid in the context of the callers (i.e., they cannot be handed to other threads). With kmap_local_page() the mappings are per thread and CPU local like in kmap_atomic(); however, they can handle page-faults and can be called from any context (including interrupts). The tasks that call kmap_local_page() can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. In calc_checksum(), the block of code between the mapping and un-mapping does not depend on the above-mentioned side effects of kmap_aatomic(), so that a mere replacements of the old API with the new one is all that is required (i.e., there is no need to explicitly call pagefault_disable() and/or preempt_disable()). Link: https://lkml.kernel.org/r/20231120141855.6761-1-fmdefrancesco@gmail.com Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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mm/ksm.c
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mm/ksm.c
@ -1099,9 +1099,9 @@ error:
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static u32 calc_checksum(struct page *page)
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static u32 calc_checksum(struct page *page)
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{
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{
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u32 checksum;
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u32 checksum;
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void *addr = kmap_atomic(page);
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void *addr = kmap_local_page(page);
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checksum = xxhash(addr, PAGE_SIZE, 0);
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checksum = xxhash(addr, PAGE_SIZE, 0);
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kunmap_atomic(addr);
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kunmap_local(addr);
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return checksum;
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return checksum;
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}
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}
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