linux-kernel - [RFC 04/10] kmod: provide wrappers for kmod

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Date:   Thu,  8 Dec 2016 11:48:24 -0800
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     shuah@...nel.org, jeyu@...hat.com, rusty@...tcorp.com.au,
        ebiederm@...ssion.com, dmitry.torokhov@...il.com, acme@...hat.com,
        corbet@....net
Cc:     martin.wilck@...e.com, mmarek@...e.com, pmladek@...e.com,
        hare@...e.com, rwright@....com, jeffm@...e.com, DSterba@...e.com,
        fdmanana@...e.com, neilb@...e.com, linux@...ck-us.net,
        rgoldwyn@...e.com, subashab@...eaurora.org, xypron.glpk@....de,
        keescook@...omium.org, atomlin@...hat.com, mbenes@...e.cz,
        paulmck@...ux.vnet.ibm.com, dan.j.williams@...el.com,
        jpoimboe@...hat.com, davem@...emloft.net, mingo@...hat.com,
        akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [RFC 04/10] kmod: provide wrappers for kmod_concurrent inc/dec

kmod_concurrent is used as an atomic counter for enabling
the allowed limit of modprobe calls, provide wrappers for it
to enable this to be expanded on more easily. This will be done
later.

Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 kernel/kmod.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index cb6f7ca7b8a5..049d7eabda38 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -44,6 +44,9 @@
 #include <trace/events/module.h>
 
 extern int max_threads;
+
+static atomic_t kmod_concurrent = ATOMIC_INIT(0);
+
 unsigned int max_modprobes;
 module_param(max_modprobes, uint, 0644);
 MODULE_PARM_DESC(max_modprobes, "Max number of allowed concurrent modprobes");
@@ -108,6 +111,20 @@ static int call_modprobe(char *module_name, int wait)
 	return -ENOMEM;
 }
 
+static int kmod_umh_threads_get(void)
+{
+	atomic_inc(&kmod_concurrent);
+	if (atomic_read(&kmod_concurrent) < max_modprobes)
+		return 0;
+	atomic_dec(&kmod_concurrent);
+	return -ENOMEM;
+}
+
+static void kmod_umh_threads_put(void)
+{
+	atomic_dec(&kmod_concurrent);
+}
+
 /**
  * __request_module - try to load a kernel module
  * @wait: wait (or not) for the operation to complete
@@ -129,7 +146,6 @@ int __request_module(bool wait, const char *fmt, ...)
 	va_list args;
 	char module_name[MODULE_NAME_LEN];
 	int ret;
-	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
 	static int kmod_loop_msg;
 
 	/*
@@ -153,8 +169,8 @@ int __request_module(bool wait, const char *fmt, ...)
 	if (ret)
 		return ret;
 
-	atomic_inc(&kmod_concurrent);
-	if (atomic_read(&kmod_concurrent) > max_modprobes) {
+	ret = kmod_umh_threads_get();
+	if (ret) {
 		/* We may be blaming an innocent here, but unlikely */
 		if (kmod_loop_msg < 5) {
 			printk(KERN_ERR
@@ -162,15 +178,14 @@ int __request_module(bool wait, const char *fmt, ...)
 			       module_name);
 			kmod_loop_msg++;
 		}
-		atomic_dec(&kmod_concurrent);
-		return -ENOMEM;
+		return ret;
 	}
 
 	trace_module_request(module_name, wait, _RET_IP_);
 
 	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
 
-	atomic_dec(&kmod_concurrent);
+	kmod_umh_threads_put();
 	return ret;
 }
 EXPORT_SYMBOL(__request_module);
-- 
2.10.1