From: Fabio M. De Francesco Date: Mon, 20 Nov 2023 14:18:44 +0000 (+0100) Subject: mm/ksm: use kmap_local_page() in calc_checksum() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b33519896664f66358cec60f6b308d80a60d1c96;p=linux.git 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 Cc: Ira Weiny Signed-off-by: Andrew Morton --- diff --git a/mm/ksm.c b/mm/ksm.c index 6a831009b4cbf..5d60d5385de67 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1099,9 +1099,9 @@ error: static u32 calc_checksum(struct page *page) { u32 checksum; - void *addr = kmap_atomic(page); + void *addr = kmap_local_page(page); checksum = xxhash(addr, PAGE_SIZE, 0); - kunmap_atomic(addr); + kunmap_local(addr); return checksum; }