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mdev: increase netlink buffer sizes

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The socket receive buffer turned out to be too small for real world
systems. Use the same size as udevd to be on the safe side. As this is
just a limit and the memory is not allocated by the kernel until really
needed there is actually no memory wasted.

Signed-off-by: Jan Klötzke <jan@kloetzke.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Jan Klötzke 2019-12-16 22:56:50 +01:00 committed by Denys Vlasenko
parent 12aa68d10f
commit 3cd55d49a2
1 changed files with 17 additions and 9 deletions
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26
util-linux/mdev.c
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@ -269,10 +269,6 @@
# define dbg3s(msg) ((void)0)
#endif
#ifndef SO_RCVBUFFORCE
#define SO_RCVBUFFORCE 33
#endif
static const char keywords[] ALIGN1 = "add\0remove\0"; // "change\0"
enum { OP_add, OP_remove };
@ -1152,15 +1148,27 @@ static void initial_scan(char *temp)
#if ENABLE_FEATURE_MDEV_DAEMON
/* uevent applet uses 16k buffer, and mmaps it before every read */
# define BUFFER_SIZE (2 * 1024)
# define RCVBUF (2 * 1024 * 1024)
/*
* The kernel (as of v5.4) will pass up to 32 environment variables with a
* total of 2kiB on each event. On top of that the action string and device
* path are added. Using a 3kiB buffer for the event should suffice in any
* case.
*
* As far as the socket receive buffer size is concerned 2MiB proved to be too
* small (see [1]). Udevd seems to use a whooping 128MiB. The socket receive
* buffer size is just a resource limit. The buffers are allocated lazily so
* the memory is not wasted.
*
* [1] http://lists.busybox.net/pipermail/busybox/2019-December/087665.html
*/
# define USER_RCVBUF (3 * 1024)
# define KERN_RCVBUF (128 * 1024 * 1024)
# define MAX_ENV 32
static void daemon_loop(char *temp, int fd)
{
for (;;) {
char netbuf[BUFFER_SIZE];
char netbuf[USER_RCVBUF];
char *env[MAX_ENV];
char *s, *end;
ssize_t len;
@ -1237,7 +1245,7 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
* mdev -d
* find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
*/
fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, RCVBUF);
fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, KERN_RCVBUF);
/*
* Make inital scan after the uevent socket is alive and