@@ -26,8 +26,14 @@ struct devres_node {
struct devres {
struct devres_node node;
- /* -- 3 pointers */
- unsigned long long data[]; /* guarantee ull alignment */
+ /*
+ * Some archs want to perform DMA into kmalloc caches
+ * and need a guaranteed alignment larger than
+ * the alignment of a 64-bit integer.
+ * Thus we use ARCH_KMALLOC_MINALIGN here and get exactly the same
+ * buffer alignment as if it was allocated by plain kmalloc().
+ */
+ u8 __aligned(ARCH_KMALLOC_MINALIGN) data[];
};
struct devres_group {
Initially we bumped into problem with 32-bit aligned atomic64_t on ARC, see [1]. And then during quite lengthly discussion Peter Z. mentioned ARCH_KMALLOC_MINALIGN which IMHO makes perfect sense. If allocation is done by plain kmalloc() obtained buffer will be ARCH_KMALLOC_MINALIGN aligned and then why buffer obtained via devm_kmalloc() should have any other alignment? This way we at least get the same behavior for both types of allocation. [1] http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004009.html [2] http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004036.html Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: David Laight <David.Laight@ACULAB.COM> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Greg KH <greg@kroah.com> Cc: <stable@vger.kernel.org> # 4.8+ --- Changes v3 -> v4: * Use ARCH_KMALLOC_MINALIGN for alignment instead of "8" [Peter] Changes v2 -> v3: * Align explicitly to 8 bytes [David] * Rephrased in-line comment [David] * Added more techinical details to commit message [Greg] * Mention more alignment options in commit message [Geert] Changes v1 -> v2: * Reworded commit message * Inserted comment right in source [Thomas] drivers/base/devres.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)