[PATCHv2] mm/zsmalloc: don't fail if can't create debugfs info

From: Dan Streetman <ddstreet@ieee.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>,
	Ganesh Mahendran <opensource.ganesh@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Seth Jennings <sjenning@redhat.com>, Yu Zhao <yuzhao@google.com>,
	Linux-MM <linux-mm@kvack.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Dan Streetman <dan.streetman@canonical.com>,
	Dan Streetman <ddstreet@ieee.org>
Subject: [PATCHv2] mm/zsmalloc: don't fail if can't create debugfs info
Date: Thu, 19 May 2016 11:18:43 -0400	[thread overview]
Message-ID: <1463671123-5479-1-git-send-email-ddstreet@ieee.org> (raw)
In-Reply-To: <CADAEsF-kaCQnNN_9gySw3J0UT4mGh8KFp75tGSJtaDAuN1T10A@mail.gmail.com>

Change the return type of zs_pool_stat_create() to void, and
remove the logic to abort pool creation if the stat debugfs
dir/file could not be created.

The debugfs stat file is for debugging/information only, and doesn't
affect operation of zsmalloc; there is no reason to abort creating
the pool if the stat file can't be created.  This was seen with
zswap, which used the same name for all pool creations, which caused
zsmalloc to fail to create a second pool for zswap if
CONFIG_ZSMALLOC_STAT was enabled.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <dan.streetman@canonical.com>
Cc: Minchan Kim <minchan@kernel.org>

---
Changes since v1:
 -add pr_warn to all stat failure cases
 -do not prevent module loading on stat failure

 mm/zsmalloc.c | 51 ++++++++++++++++++++++-----------------------------
 1 file changed, 22 insertions(+), 29 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index aba39a2..b6d4f25 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -45,6 +45,8 @@
  *
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
@@ -483,16 +485,16 @@ static inline unsigned long zs_stat_get(struct size_class *class,
 
 #ifdef CONFIG_ZSMALLOC_STAT
 
-static int __init zs_stat_init(void)
+static void __init zs_stat_init(void)
 {
-	if (!debugfs_initialized())
-		return -ENODEV;
+	if (!debugfs_initialized()) {
+		pr_warn("debugfs not available, stat dir not created\n");
+		return;
+	}
 
 	zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
 	if (!zs_stat_root)
-		return -ENOMEM;
-
-	return 0;
+		pr_warn("debugfs 'zsmalloc' stat dir creation failed\n");
 }
 
 static void __exit zs_stat_exit(void)
@@ -573,17 +575,19 @@ static const struct file_operations zs_stat_size_ops = {
 	.release        = single_release,
 };
 
-static int zs_pool_stat_create(struct zs_pool *pool, const char *name)
+static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 {
 	struct dentry *entry;
 
-	if (!zs_stat_root)
-		return -ENODEV;
+	if (!zs_stat_root) {
+		pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
+		return;
+	}
 
 	entry = debugfs_create_dir(name, zs_stat_root);
 	if (!entry) {
 		pr_warn("debugfs dir <%s> creation failed\n", name);
-		return -ENOMEM;
+		return;
 	}
 	pool->stat_dentry = entry;
 
@@ -592,10 +596,9 @@ static int zs_pool_stat_create(struct zs_pool *pool, const char *name)
 	if (!entry) {
 		pr_warn("%s: debugfs file entry <%s> creation failed\n",
 				name, "classes");
-		return -ENOMEM;
+		debugfs_remove_recursive(pool->stat_dentry);
+		pool->stat_dentry = NULL;
 	}
-
-	return 0;
 }
 
 static void zs_pool_stat_destroy(struct zs_pool *pool)
@@ -604,18 +607,16 @@ static void zs_pool_stat_destroy(struct zs_pool *pool)
 }
 
 #else /* CONFIG_ZSMALLOC_STAT */
-static int __init zs_stat_init(void)
+static void __init zs_stat_init(void)
 {
-	return 0;
 }
 
 static void __exit zs_stat_exit(void)
 {
 }
 
-static inline int zs_pool_stat_create(struct zs_pool *pool, const char *name)
+static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 {
-	return 0;
 }
 
 static inline void zs_pool_stat_destroy(struct zs_pool *pool)
@@ -623,7 +624,6 @@ static inline void zs_pool_stat_destroy(struct zs_pool *pool)
 }
 #endif
 
-
 /*
  * For each size class, zspages are divided into different groups
  * depending on how "full" they are. This was done so that we could
@@ -1952,8 +1952,8 @@ struct zs_pool *zs_create_pool(const char *name)
 		prev_class = class;
 	}
 
-	if (zs_pool_stat_create(pool, name))
-		goto err;
+	/* debug only, don't abort if it fails */
+	zs_pool_stat_create(pool, name);
 
 	/*
 	 * Not critical, we still can use the pool
@@ -2015,17 +2015,10 @@ static int __init zs_init(void)
 	zpool_register_driver(&zs_zpool_driver);
 #endif
 
-	ret = zs_stat_init();
-	if (ret) {
-		pr_err("zs stat initialization failed\n");
-		goto stat_fail;
-	}
+	zs_stat_init();
+
 	return 0;
 
-stat_fail:
-#ifdef CONFIG_ZPOOL
-	zpool_unregister_driver(&zs_zpool_driver);
-#endif
 notifier_fail:
 	zs_unregister_cpu_notifier();
 
-- 
2.7.4
