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PM: hibernate: Replace deprecated kmap_atomic() with kmap_local_page()

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kmap_atomic() is deprecated and should be replaced with kmap_local_page()
[1][2]. kmap_local_page() is faster in kernels with HIGHMEM enabled, can
take page faults, and allows preemption.

According to [2], this replacement is safe as long as the code between
kmap_atomic() and kunmap_atomic() does not implicitly depend on disabling
page faults or preemption. In all of the call sites in this patch, the only
thing happening between mapping and unmapping pages is copy_page() calls,
and I don't suspect they depend on disabling page faults or preemption.

Link: https://lwn.net/Articles/836144/ [1]
Link: https://docs.kernel.org/mm/highmem.html#temporary-virtual-mappings [2]
Signed-off-by: David Reaver <me@davidreaver.com>
Link: https://patch.msgid.link/20250112152658.20132-1-me@davidreaver.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
David Reaver 2025-01-12 07:26:55 -08:00 committed by Rafael J. Wysocki
parent 0ad2507d5d
commit d42044aad6
1 changed files with 8 additions and 8 deletions
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16
kernel/power/snapshot.c
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@ -2270,9 +2270,9 @@ int snapshot_read_next(struct snapshot_handle *handle)
*/
void *kaddr;
kaddr = kmap_atomic(page);
kaddr = kmap_local_page(page);
copy_page(buffer, kaddr);
kunmap_atomic(kaddr);
kunmap_local(kaddr);
handle->buffer = buffer;
} else {
handle->buffer = page_address(page);
@ -2561,9 +2561,9 @@ static void copy_last_highmem_page(void)
if (last_highmem_page) {
void *dst;
dst = kmap_atomic(last_highmem_page);
dst = kmap_local_page(last_highmem_page);
copy_page(dst, buffer);
kunmap_atomic(dst);
kunmap_local(dst);
last_highmem_page = NULL;
}
}
@ -2881,13 +2881,13 @@ static inline void swap_two_pages_data(struct page *p1, struct page *p2,
{
void *kaddr1, *kaddr2;
kaddr1 = kmap_atomic(p1);
kaddr2 = kmap_atomic(p2);
kaddr1 = kmap_local_page(p1);
kaddr2 = kmap_local_page(p2);
copy_page(buf, kaddr1);
copy_page(kaddr1, kaddr2);
copy_page(kaddr2, buf);
kunmap_atomic(kaddr2);
kunmap_atomic(kaddr1);
kunmap_local(kaddr2);
kunmap_local(kaddr1);
}
/**