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mm/mempool: replace kmap_atomic() with kmap_local_page()

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kmap_atomic() has been deprecated in favor of kmap_local_page().

Therefore, replace kmap_atomic() with kmap_local_page().

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.

The code blocks between the mappings and un-mappings don't rely on the
above-mentioned side effects of kmap_atomic(), so that mere replacements
of the old API with the new one is all that they require (i.e., there is
no need to explicitly call pagefault_disable() and/or preempt_disable()).

Link: https://lkml.kernel.org/r/20231120142640.7077-1-fabio.maria.de.francesco@linux.intel.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>
This commit is contained in:
Fabio M. De Francesco 2023-11-20 15:26:31 +01:00 committed by Andrew Morton
parent 24d2613a63
commit f2bcc99a5e
1 changed files with 4 additions and 4 deletions
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8
mm/mempool.c
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@ -64,10 +64,10 @@ static void check_element(mempool_t *pool, void *element)
} else if (pool->free == mempool_free_pages) {
/* Mempools backed by page allocator */
int order = (int)(long)pool->pool_data;
void *addr = kmap_atomic((struct page *)element);
void *addr = kmap_local_page((struct page *)element);
__check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
kunmap_atomic(addr);
kunmap_local(addr);
}
}
@ -89,10 +89,10 @@ static void poison_element(mempool_t *pool, void *element)
} else if (pool->alloc == mempool_alloc_pages) {
/* Mempools backed by page allocator */
int order = (int)(long)pool->pool_data;
void *addr = kmap_atomic((struct page *)element);
void *addr = kmap_local_page((struct page *)element);
__poison_element(addr, 1UL << (PAGE_SHIFT + order));
kunmap_atomic(addr);
kunmap_local(addr);
}
}
#else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */