[PATCH] sparc: clarify __GFP_NOFAIL allocation

[Michal Hocko]

920c3ed74134 ([SPARC64]: Add basic infrastructure for MD add/remove
notification.) has added __GFP_NOFAIL for the allocation request but
it hasn't mentioned why is this strict requirement really needed.
The code was handling an allocation failure and propagated it properly
up the callchain so it is not clear why it is needed.

Dave has clarified the intention when I tried to remove the flag as not
being necessary:
"
It is a serious failure.

If we miss an MDESC update due to this allocation failure, the update
is not an event which gets retransmitted so we will lose the updated
machine description forever.

We really need this allocation to succeed.
"

So add a comment to clarify the nofail flag and get rid of the failure
check because __GFP_NOFAIL allocation doesn't fail.

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
 arch/sparc/kernel/mdesc.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
index 99632a87e697..26c80e18d7b1 100644
--- a/arch/sparc/kernel/mdesc.c
+++ b/arch/sparc/kernel/mdesc.c
@@ -130,26 +130,26 @@ static struct mdesc_mem_ops memblock_mdesc_ops = {
 static struct mdesc_handle *mdesc_kmalloc(unsigned int mdesc_size)
 {
 	unsigned int handle_size;
+	struct mdesc_handle *hp;
+	unsigned long addr;
 	void *base;
 
 	handle_size = (sizeof(struct mdesc_handle) -
 		       sizeof(struct mdesc_hdr) +
 		       mdesc_size);
 
+	/*
+	 * Allocation has to succeed because mdesc update would be missed
+	 * and such events are not retransmitted.
+	 */
 	base = kmalloc(handle_size + 15, GFP_KERNEL | __GFP_NOFAIL);
-	if (base) {
-		struct mdesc_handle *hp;
-		unsigned long addr;
-
-		addr = (unsigned long)base;
-		addr = (addr + 15UL) & ~15UL;
-		hp = (struct mdesc_handle *) addr;
+	addr = (unsigned long)base;
+	addr = (addr + 15UL) & ~15UL;
+	hp = (struct mdesc_handle *) addr;
 
-		mdesc_handle_init(hp, handle_size, base);
-		return hp;
-	}
+	mdesc_handle_init(hp, handle_size, base);
 
-	return NULL;
+	return hp;
 }
 
 static void mdesc_kfree(struct mdesc_handle *hp)
-- 
2.1.4


-- 
Michal Hocko
SUSE Labs
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