From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Wed, 25 May 2011 21:13:18 +0000 (-0700)
Subject: Fix stack ddt_zap_lookup()
X-Git-Tag: zfs-0.6.0-rc5~53
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5b8c7bbcea7ad9ecd5f329d2d736cba8402ee781;p=zfs

Fix stack ddt_zap_lookup()

Stack usage for ddt_zap_lookup() reduced from 368 bytes to 120
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_zap.c b/module/zfs/ddt_zap.c
index d6a991c7c..280bff35a 100644
--- a/module/zfs/ddt_zap.c
+++ b/module/zfs/ddt_zap.c
@@ -58,14 +58,16 @@ ddt_zap_destroy(objset_t *os, uint64_t object, dmu_tx_t *tx)
 static int
 ddt_zap_lookup(objset_t *os, uint64_t object, ddt_entry_t *dde)
 {
-	uchar_t cbuf[sizeof (dde->dde_phys) + 1];
+	uchar_t *cbuf;
 	uint64_t one, csize;
 	int error;
 
+	cbuf = kmem_alloc(sizeof (dde->dde_phys) + 1, KM_SLEEP);
+
 	error = zap_length_uint64(os, object, (uint64_t *)&dde->dde_key,
 	    DDT_KEY_WORDS, &one, &csize);
 	if (error)
-		return (error);
+		goto out;
 
 	ASSERT(one == 1);
 	ASSERT(csize <= sizeof (cbuf));
@@ -73,11 +75,13 @@ ddt_zap_lookup(objset_t *os, uint64_t object, ddt_entry_t *dde)
 	error = zap_lookup_uint64(os, object, (uint64_t *)&dde->dde_key,
 	    DDT_KEY_WORDS, 1, csize, cbuf);
 	if (error)
-		return (error);
+		goto out;
 
 	ddt_decompress(cbuf, dde->dde_phys, csize, sizeof (dde->dde_phys));
+out:
+	kmem_free(cbuf, sizeof (dde->dde_phys) + 1);
 
-	return (0);
+	return (error);
 }
 
 static void