[patch] slab: always follow arch requested alignments

[Heiko Carstens]

From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>

In kmem_cache_create(): always check if BYTES_PER_WORD is less than
ARCH_SLAB_MINALIGN and disable debug options that would set the
alignment to BYTES_PER_WORD.
This will make sure that all slab caches will have at least an
ARCH_SLAB_MINALIGN alignment.

In addition make sure that a caller mandated align which is greater
than BYTES_PER_WORD also disables the same debug options.
This makes sure that ARCH_KMALLOC_MINALIGN also has an effect if
CONFIG_DEBUG_SLAB is set.

Cc: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---

 mm/slab.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/slab.c b/mm/slab.c
index 0f20843..1f6fc04 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2103,12 +2103,18 @@ #endif
 		if (ralign > BYTES_PER_WORD)
 			flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
 	}
+	if (BYTES_PER_WORD < ARCH_SLAB_MINALIGN)
+		flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
+
 	/* 3) caller mandated alignment: disables debug if necessary */
 	if (ralign < align) {
 		ralign = align;
 		if (ralign > BYTES_PER_WORD)
 			flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
 	}
+	if (align > BYTES_PER_WORD)
+		flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
+
 	/*
 	 * 4) Store it. Note that the debug code below can reduce
 	 *    the alignment to BYTES_PER_WORD.
-
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