mqueue: separate mqueue default value from maximum value

Commit b231cca4381e ("message queues: increase range limits") changed
mqueue default value when attr parameter is specified NULL from hard
coded value to fs.mqueue.{msg,msgsize}_max sysctl value.

This made large side effect.  When user need to use two mqueue
applications 1) using !NULL attr parameter and it require big message
size and 2) using NULL attr parameter and only need small size message,
app (1) require to raise fs.mqueue.msgsize_max and app (2) consume large
memory size even though it doesn't need.

Doug Ledford propsed to switch back it to static hard coded value.
However it also has a compatibility problem.  Some applications might
started depend on the default value is tunable.

The solution is to separate default value from maximum value.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Acked-by: Doug Ledford <dledford@redhat.com>
Acked-by: Joe Korty <joe.korty@ccur.com>
Cc: Amerigo Wang <amwang@redhat.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
index 88fd7f5c8dcd61307171b3af852541d06a984380..13d6166d7a2798fbd54b39a90b533ad5ddebe9eb 100644 (file)
--- a/Documentation/sysctl/fs.txt
+++ b/Documentation/sysctl/fs.txt
@@ -225,6 +225,13 @@ a queue must be less or equal then msg_max.
 maximum  message size value (it is every  message queue's attribute set during
 its creation).
 
+/proc/sys/fs/mqueue/msg_default is  a read/write  file for setting/getting the
+default number of messages in a queue value if attr parameter of mq_open(2) is
+NULL. If it exceed msg_max, the default value is initialized msg_max.
+
+/proc/sys/fs/mqueue/msgsize_default is a read/write file for setting/getting
+the default message size value if attr parameter of mq_open(2) is NULL. If it
+exceed msgsize_max, the default value is initialized msgsize_max.
 
 4. /proc/sys/fs/epoll - Configuration options for the epoll interface
 --------------------------------------------------------

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 2488535a32a383e9d8fdd04a8f9fc41ae265de09..5499c92a91539afcc0987d49fe6477acad2d16e4 100644 (file)
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -62,6 +62,8 @@ struct ipc_namespace {
        unsigned int    mq_queues_max;   /* initialized to DFLT_QUEUESMAX */
        unsigned int    mq_msg_max;      /* initialized to DFLT_MSGMAX */
        unsigned int    mq_msgsize_max;  /* initialized to DFLT_MSGSIZEMAX */
+       unsigned int    mq_msg_default;
+       unsigned int    mq_msgsize_default;
 
        /* user_ns which owns the ipc ns */
        struct user_namespace *user_ns;

diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index e22336a09b4a7932c0a5de4615fb4c7de9a98687..383d638340b8417c8e31f53b935f8e8d833b2707 100644 (file)
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -73,6 +73,24 @@ static ctl_table mq_sysctls[] = {
                .extra1         = &msg_maxsize_limit_min,
                .extra2         = &msg_maxsize_limit_max,
        },
+       {
+               .procname       = "msg_default",
+               .data           = &init_ipc_ns.mq_msg_default,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = proc_mq_dointvec_minmax,
+               .extra1         = &msg_max_limit_min,
+               .extra2         = &msg_max_limit_max,
+       },
+       {
+               .procname       = "msgsize_default",
+               .data           = &init_ipc_ns.mq_msgsize_default,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = proc_mq_dointvec_minmax,
+               .extra1         = &msg_maxsize_limit_min,
+               .extra2         = &msg_maxsize_limit_max,
+       },
        {}
 };
 

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 6828e2c93cef5c7a79ad7135ae386e2c2421fd3e..609d53f7a915f339f9934e1725e02c80b9df433e 100644 (file)
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -145,9 +145,10 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
                info->qsize = 0;
                info->user = NULL;      /* set when all is ok */
                memset(&info->attr, 0, sizeof(info->attr));
-               info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max, DFLT_MSG);
-               info->attr.mq_msgsize =
-                       min(ipc_ns->mq_msgsize_max, DFLT_MSGSIZE);
+               info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
+                                          ipc_ns->mq_msg_default);
+               info->attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
+                                           ipc_ns->mq_msgsize_default);
                if (attr) {
                        info->attr.mq_maxmsg = attr->mq_maxmsg;
                        info->attr.mq_msgsize = attr->mq_msgsize;
@@ -1261,6 +1262,8 @@ int mq_init_ns(struct ipc_namespace *ns)
        ns->mq_queues_max    = DFLT_QUEUESMAX;
        ns->mq_msg_max       = DFLT_MSGMAX;
        ns->mq_msgsize_max   = DFLT_MSGSIZEMAX;
+       ns->mq_msg_default   = DFLT_MSG;
+       ns->mq_msgsize_default  = DFLT_MSGSIZE;
 
        ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
        if (IS_ERR(ns->mq_mnt)) {