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authorFabio M. De Francesco <fmdefrancesco@gmail.com>2022-04-25 19:57:54 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-04-26 12:51:31 +0200
commite88a6a8fece9b92be4f55735134a022061e6e68b (patch)
treeddadbbdf7e9e41c963927058f1fe1513d90c852e /drivers/android
parent1d625960e41907af706f573a3cd097595a0ade63 (diff)
binder: Use memcpy_{to,from}_page() in binder_alloc_do_buffer_copy()
The use of kmap_atomic() is being deprecated in favor of kmap_local_page() where it is feasible. Each call of kmap_atomic() in the kernel creates a non-preemptible section and disable pagefaults. This could be a source of unwanted latency, so kmap_local_page() should be preferred. With kmap_local_page(), the mapping is per thread, CPU local and not globally visible. Furthermore, the mapping can be acquired from any context (including interrupts). binder_alloc_do_buffer_copy() is a function where the use of kmap_local_page() in place of kmap_atomic() is correctly suited. Use kmap_local_page() / kunmap_local() in place of kmap_atomic() / kunmap_atomic() but, instead of open coding the mappings and call memcpy() to and from the virtual addresses of the mapped pages, prefer the use of the memcpy_{to,from}_page() wrappers (as suggested by Christophe Jaillet). Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Acked-by: Todd Kjos <tkjos@google.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Link: https://lore.kernel.org/r/20220425175754.8180-4-fmdefrancesco@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android')
-rw-r--r--drivers/android/binder_alloc.c13
1 files changed, 2 insertions, 11 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 0875c463c002..5649a0371a1f 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1244,23 +1244,14 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
unsigned long size;
struct page *page;
pgoff_t pgoff;
- void *tmpptr;
- void *base_ptr;
page = binder_alloc_get_page(alloc, buffer,
buffer_offset, &pgoff);
size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
- base_ptr = kmap_atomic(page);
- tmpptr = base_ptr + pgoff;
if (to_buffer)
- memcpy(tmpptr, ptr, size);
+ memcpy_to_page(page, pgoff, ptr, size);
else
- memcpy(ptr, tmpptr, size);
- /*
- * kunmap_atomic() takes care of flushing the cache
- * if this device has VIVT cache arch
- */
- kunmap_atomic(base_ptr);
+ memcpy_from_page(ptr, page, pgoff, size);
bytes -= size;
pgoff = 0;
ptr = ptr + size;