From: Tom Caputi <tcaputi@datto.com>
Date: Tue, 15 Jan 2019 20:23:40 +0000 (-0500)
Subject: Fix zio leak in dbuf_read()
X-Git-Tag: zfs-0.8.0-rc4~170
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5e7f3ace5807f950f3529361e03970101e61aa44;p=zfs

Fix zio leak in dbuf_read()

Currently, dbuf_read() may decide to create a zio_root which is
used as a parent for any child zios created in dbuf_read_impl().
However, if there is an error in dbuf_read_impl(), this zio is
never executed and ends up leaked. This patch simply ensures
that we always execute the root zio, even i it has no real work
to do.

Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #8267
---

diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index a22fbdc11..826934b36 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -1565,8 +1565,17 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 		DB_DNODE_EXIT(db);
 		DBUF_STAT_BUMP(hash_misses);
 
-		if (!err && need_wait)
-			err = zio_wait(zio);
+		/*
+		 * If we created a zio_root we must execute it to avoid
+		 * leaking it, even if it isn't attached to any work due
+		 * to an error in dbuf_read_impl().
+		 */
+		if (need_wait) {
+			if (err == 0)
+				err = zio_wait(zio);
+			else
+				VERIFY0(zio_wait(zio));
+		}
 	} else {
 		/*
 		 * Another reader came in while the dbuf was in flight