From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Wed, 25 May 2011 20:56:40 +0000 (-0700)
Subject: Fix stack ddt_class_contains()
X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=commitdiff_plain;ds=sidebyside;h=e95b3bdcbbc64ea502349413234e7c71563e7115;p=zfs.git

Fix stack ddt_class_contains()

Stack usage for ddt_class_contains() reduced from 524 bytes to 68
bytes.  This large stack allocation significantly contributed to
the likelyhood of a stack overflow when scrubbing/resilvering
dedup pools.
---

diff --git a/module/zfs/ddt.c b/module/zfs/ddt.c
index 49428d1..7279f1d 100644
--- a/module/zfs/ddt.c
+++ b/module/zfs/ddt.c
@@ -891,7 +891,7 @@ boolean_t
 ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 {
 	ddt_t *ddt;
-	ddt_entry_t dde;
+	ddt_entry_t *dde;
 	enum ddt_type type;
 	enum ddt_class class;
 
@@ -902,14 +902,20 @@ ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 		return (B_TRUE);
 
 	ddt = spa->spa_ddt[BP_GET_CHECKSUM(bp)];
+	dde = kmem_alloc(sizeof(ddt_entry_t), KM_SLEEP);
 
-	ddt_key_fill(&dde.dde_key, bp);
+	ddt_key_fill(&(dde->dde_key), bp);
 
-	for (type = 0; type < DDT_TYPES; type++)
-		for (class = 0; class <= max_class; class++)
-			if (ddt_object_lookup(ddt, type, class, &dde) == 0)
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class <= max_class; class++) {
+			if (ddt_object_lookup(ddt, type, class, dde) == 0) {
+				kmem_free(dde, sizeof(ddt_entry_t));
 				return (B_TRUE);
+			}
+		}
+	}
 
+	kmem_free(dde, sizeof(ddt_entry_t));
 	return (B_FALSE);
 }