LKML Archive on lore.kernel.org
 help / color / Atom feed
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: akpm@linux-foundation.org, jeyu@redhat.com, shuah@kernel.org,
	rusty@rustcorp.com.au, ebiederm@xmission.com,
	dmitry.torokhov@gmail.com, acme@redhat.com, corbet@lwn.net
Cc: martin.wilck@suse.com, mmarek@suse.com, pmladek@suse.com,
	hare@suse.com, rwright@hpe.com, jeffm@suse.com, DSterba@suse.com,
	fdmanana@suse.com, neilb@suse.com, linux@roeck-us.net,
	rgoldwyn@suse.com, subashab@codeaurora.org, xypron.glpk@gmx.de,
	keescook@chromium.org, atomlin@redhat.com, mbenes@suse.cz,
	paulmck@linux.vnet.ibm.com, dan.j.williams@intel.com,
	jpoimboe@redhat.com, davem@davemloft.net, mingo@redhat.com,
	alan@linux.intel.com, tytso@mit.edu, gregkh@linuxfoundation.org,
	torvalds@linux-foundation.org, linux-kselftest@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	Tom Gundersen <teg@jklm.no>
Subject: [PATCH v2 4/5] kmod: add helpers for getting kmod limit
Date: Thu, 25 May 2017 17:16:29 -0700
Message-ID: <20170526001630.19203-5-mcgrof@kernel.org> (raw)
In-Reply-To: <20170526001630.19203-1-mcgrof@kernel.org>

This adds helpers for getting access to the kmod limit from
userspace. This knob should help userspace more gracefully and
deterministically handle module loading.

Cc: Tom Gundersen <teg@jklm.no>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 Documentation/sysctl/kernel.txt | 20 ++++++++++++++++++++
 include/linux/kmod.h            |  5 +++++
 kernel/kmod.c                   | 33 +++++++++++++++++++++++++++++++++
 kernel/sysctl.c                 |  7 +++++++
 4 files changed, 65 insertions(+)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index bac23c198360..080ccdca1f10 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -370,6 +370,26 @@ with the "modules_disabled" sysctl.
 
 ==============================================================
 
+kmod-limit:
+
+Get the max amount of concurrent requests (kmod_concurrent) the kernel can
+make out to userspace to call 'modprobe'. This limit is known internally to the
+kernel as max_modprobes. This interface is designed to enable userspace to
+query the kernel for the max_modprobes limit so userspace can more
+deterministically handle module loading by only enabling max_modprobes
+'modprobe' calls at a time.
+
+Dependencies are resolved in userspace through depmod, so one modprobe
+call only bumps the number of concurrent threads (kmod_concurrent) by one.
+Dependencies for a module then are loaded directly in userspace using
+init_module() / finit_module() skipping bumping kmod_concurrent or being
+affected by max_modprobes.
+
+The max_modprobes value is set at build time with CONFIG_MAX_KMOD_CONCURRENT.
+You can override at initialization with the module parameter max_modprobes.
+
+==============================================================
+
 kptr_restrict:
 
 This toggle indicates whether restrictions are placed on
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 8e2f302b214a..bbc6d59190aa 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -39,13 +39,18 @@ int __request_module(bool wait, const char *name, ...);
 #define try_then_request_module(x, mod...) \
 	((x) ?: (__request_module(true, mod), (x)))
 void init_kmod_umh(void);
+unsigned int get_kmod_umh_limit(void);
+int sysctl_kmod_limit(struct ctl_table *table, int write,
+		      void __user *buffer, size_t *lenp, loff_t *ppos);
 #else
 static inline int request_module(const char *name, ...) { return -ENOSYS; }
 static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; }
 #define try_then_request_module(x, mod...) (x)
 static inline void init_kmod_umh(void) { }
+static inline unsigned int get_kmod_umh_limit(void) { return 0; }
 #endif
 
+#define get_kmod_umh_limit get_kmod_umh_limit
 
 struct cred;
 struct file;
diff --git a/kernel/kmod.c b/kernel/kmod.c
index cafd27b92d19..17de776cf368 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -111,6 +111,17 @@ static int call_modprobe(char *module_name, int wait)
 }
 
 /**
+ * get_kmod_umh_limit - get concurrent modprobe thread limit
+ *
+ * Returns the number of allowed concurrent modprobe calls.
+ */
+unsigned int get_kmod_umh_limit(void)
+{
+	return max_modprobes;
+}
+EXPORT_SYMBOL_GPL(get_kmod_umh_limit);
+
+/**
  * __request_module - try to load a kernel module
  * @wait: wait (or not) for the operation to complete
  * @fmt: printf style format string for the name of the module
@@ -194,6 +205,28 @@ void __init init_kmod_umh(void)
 	atomic_set(&kmod_concurrent_max, max_modprobes);
 }
 
+int sysctl_kmod_limit(struct ctl_table *table, int write,
+		      void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table t;
+	int ret;
+	unsigned int local_max_modprobes = max_modprobes;
+	unsigned int min = 0;
+	unsigned int max = max_threads/2;
+
+	t = *table;
+	t.data = &local_max_modprobes;
+	t.extra1 = &min;
+	t.extra2 = &max;
+
+	if (write)
+		return -EPERM;
+
+	ret = proc_douintvec_minmax(&t, write, buffer, lenp, ppos);
+
+	return ret;
+}
+
 #endif /* CONFIG_MODULES */
 
 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index df9f2a367882..d1c1d1999bb1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -682,6 +682,13 @@ static struct ctl_table kern_table[] = {
 		.extra1		= &one,
 		.extra2		= &one,
 	},
+	{
+		.procname	= "kmod-limit",
+		.data		= NULL, /* filled in by handler */
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0444,
+		.proc_handler	= sysctl_kmod_limit,
+	},
 #endif
 #ifdef CONFIG_UEVENT_HELPER
 	{
-- 
2.11.0

  parent reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-19  3:24 [PATCH 0/6] kmod: few simple enhancements Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 1/6] kmod: add dynamic max concurrent thread count Luis R. Rodriguez
2017-05-19 20:44   ` Dmitry Torokhov
     [not found]     ` <CAB=NE6XGL24O+JfTNUG0HO4obhDc-v+HyL0SCrQELiZrj2-qNw@mail.gmail.com>
     [not found]       ` <CAB=NE6Wa4Nemh80yaCCwbjrNRLPD+GJMncg12APg9Vq63AWVng@mail.gmail.com>
     [not found]         ` <CAB=NE6Vc6RDAytn2Pkv2V58HFo8ncR0eOHZ3===kbZ2NF78ubg@mail.gmail.com>
     [not found]           ` <CAB=NE6Vqmx=y6muenpuQKynTP=pGWMF8tzoCA0BXD6d63q9wPg@mail.gmail.com>
2017-05-19 21:58             ` Dmitry Torokhov
2017-05-25 16:22               ` Luis R. Rodriguez
2017-05-25 16:38                 ` Dmitry Torokhov
2017-05-25 16:50                   ` Luis R. Rodriguez
2017-05-25 17:30                     ` Dmitry Torokhov
2017-05-25 17:38                       ` Luis R. Rodriguez
2017-05-25 18:06                         ` Luis R. Rodriguez
2017-05-25 18:26                           ` Dmitry Torokhov
2017-05-25 19:01                             ` Luis R. Rodriguez
2017-05-25 21:38                               ` Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 2/6] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-23 14:46   ` Miroslav Benes
2017-05-19  3:24 ` [PATCH 3/6] kmod: provide wrappers for kmod_concurrent inc/dec Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 4/6] kmod: return -EBUSY if modprobe limit is reached Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 5/6] kmod: preempt on kmod_umh_threads_get() Luis R. Rodriguez
2017-05-19 22:27   ` Dmitry Torokhov
2017-05-25  0:14     ` Luis R. Rodriguez
2017-05-25  0:45       ` Dmitry Torokhov
2017-05-25  1:00         ` Luis R. Rodriguez
2017-05-25  2:27           ` Dmitry Torokhov
2017-05-25 11:19             ` Petr Mladek
2017-05-25 15:38               ` Luis R. Rodriguez
2017-05-25 16:42               ` Dmitry Torokhov
2017-05-25 15:18             ` Jessica Yu
2017-05-19  3:24 ` [PATCH 6/6] kmod: use simplified rate limit printk Luis R. Rodriguez
2017-05-19 22:23   ` Dmitry Torokhov
2017-05-23  9:00     ` Petr Mladek
2017-05-26  0:16 ` [PATCH v2 0/5] kmod: help make deterministic Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 1/5] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 2/5] kmod: reduce atomic operations on kmod_concurrent Luis R. Rodriguez
2017-05-26  1:11     ` Dmitry Torokhov
2017-05-26 20:03       ` Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 3/5] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-05-26  0:16   ` Luis R. Rodriguez [this message]
2017-05-26  0:56     ` [PATCH v2 4/5] kmod: add helpers for getting kmod limit Dmitry Torokhov
2017-05-26 20:27       ` Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 5/5] kmod: throttle kmod thread limit Luis R. Rodriguez
2017-05-26 21:12   ` [PATCH v3 0/4] kmod: help make deterministic Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 1/4] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 2/4] kmod: reduce atomic operations on kmod_concurrent and simplify Luis R. Rodriguez
2017-06-23 19:19       ` [PATCH v4 " Luis R. Rodriguez
2017-06-26 11:36       ` [PATCH v3 " Petr Mladek
2017-05-26 21:12     ` [PATCH v3 3/4] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 4/4] kmod: throttle kmod thread limit Luis R. Rodriguez
2017-06-22 15:19       ` Petr Mladek
2017-06-23 16:16         ` Luis R. Rodriguez
2017-06-23 17:56           ` Luis R. Rodriguez
2017-06-23 19:16             ` Luis R. Rodriguez
2017-06-26 10:03               ` Petr Mladek
2017-06-26  9:55           ` Petr Mladek
2017-06-23 19:20       ` [PATCH v4 " Luis R. Rodriguez
2017-06-26 11:38         ` Petr Mladek
2017-06-28 22:11           ` Luis R. Rodriguez
2017-06-20 20:56     ` [PATCH v3 0/4] kmod: help make deterministic Luis R. Rodriguez
2017-06-21  0:23       ` Kees Cook
2017-06-26 21:37         ` Jessica Yu
2017-06-26 22:44           ` Luis R. Rodriguez
2017-06-27  0:27             ` Luis R. Rodriguez
2017-06-27  8:13               ` Petr Mladek
2017-06-27 10:04                 ` Jessica Yu
2017-06-27 15:26             ` Jessica Yu
2017-06-28  0:49               ` Luis R. Rodriguez
2017-06-28 22:31     ` [PATCH v4 0/3] " Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 1/3] MAINTAINERS: give kmod some maintainer love Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 2/3] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 3/3] kmod: throttle kmod thread limit Luis R. Rodriguez

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170526001630.19203-5-mcgrof@kernel.org \
    --to=mcgrof@kernel.org \
    --cc=DSterba@suse.com \
    --cc=acme@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=alan@linux.intel.com \
    --cc=atomlin@redhat.com \
    --cc=corbet@lwn.net \
    --cc=dan.j.williams@intel.com \
    --cc=davem@davemloft.net \
    --cc=dmitry.torokhov@gmail.com \
    --cc=ebiederm@xmission.com \
    --cc=fdmanana@suse.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=hare@suse.com \
    --cc=jeffm@suse.com \
    --cc=jeyu@redhat.com \
    --cc=jpoimboe@redhat.com \
    --cc=keescook@chromium.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux@roeck-us.net \
    --cc=martin.wilck@suse.com \
    --cc=mbenes@suse.cz \
    --cc=mingo@redhat.com \
    --cc=mmarek@suse.com \
    --cc=neilb@suse.com \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=pmladek@suse.com \
    --cc=rgoldwyn@suse.com \
    --cc=rusty@rustcorp.com.au \
    --cc=rwright@hpe.com \
    --cc=shuah@kernel.org \
    --cc=subashab@codeaurora.org \
    --cc=teg@jklm.no \
    --cc=torvalds@linux-foundation.org \
    --cc=tytso@mit.edu \
    --cc=xypron.glpk@gmx.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git