lib: replace kmap() with kmap_local_page()
kmap() has been deprecated in favor of the kmap_local_page() due to high cost, restricted mapping space, the overhead of a global lock for synchronization, and making the process sleep in the absence of free slots. kmap_local_page() is faster than kmap() and offers thread-local and CPU-local mappings, take pagefaults in a local kmap region and preserves preemption by saving the mappings of outgoing tasks and restoring those of the incoming one during a context switch. The mappings are kept thread local in the functions “dmirror_do_read” and “dmirror_do_write” in test_hmm.c Therefore, replace kmap() with kmap_local_page() and use mempcy_from/to_page() to avoid open coding kmap_local_page() + memcpy() + kunmap_local(). Remove the unused variable “tmp”. Link: https://lkml.kernel.org/r/20230610175712.GA348514@sumitra.com Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Cc: Deepak R Varma <drv@mailo.com> Cc: Jérôme Glisse <jglisse@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -368,16 +368,13 @@ static int dmirror_do_read(struct dmirror *dmirror, unsigned long start,
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for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
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void *entry;
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struct page *page;
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void *tmp;
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entry = xa_load(&dmirror->pt, pfn);
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page = xa_untag_pointer(entry);
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if (!page)
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return -ENOENT;
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tmp = kmap(page);
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memcpy(ptr, tmp, PAGE_SIZE);
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kunmap(page);
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memcpy_from_page(ptr, page, 0, PAGE_SIZE);
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ptr += PAGE_SIZE;
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bounce->cpages++;
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@ -437,16 +434,13 @@ static int dmirror_do_write(struct dmirror *dmirror, unsigned long start,
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for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
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void *entry;
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struct page *page;
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void *tmp;
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entry = xa_load(&dmirror->pt, pfn);
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page = xa_untag_pointer(entry);
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if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE)
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return -ENOENT;
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tmp = kmap(page);
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memcpy(tmp, ptr, PAGE_SIZE);
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kunmap(page);
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memcpy_to_page(page, 0, ptr, PAGE_SIZE);
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ptr += PAGE_SIZE;
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bounce->cpages++;
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