[OpenWrt-Devel] [PATCH V3 fstools] block: generate hotplug.d mount events

[Rafał Miłecki]

From: Rafał Miłecki <rafal at milecki.pl>

With this change block generates 2 "mount" hotplug.d subsystem events:
1) "add" when block device gets mounted
2) "remove" when block device gets unmounted

This allows e.g. controlling USB storage dependant software using
hotplug.d listeners.

A very similar solution was implemented in mountd which was replaced by
blockd.

Right now this is implemented using a call to the /sbin/hotplug-call.
A possible improvement is to rewrite above shell script into a C lib
function. For now let's just assume that script exists.

Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
V2: Use hotplug_call() helper. It requires
    [PATCH libubox] hotplug: add hotplug_call() helper
V3: Switch back to the local hotplug-call call as it doesn't really fit
    the library.
    Use setenv() which simplifies the code.
    Improve error handling.
---
 block.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/block.c b/block.c
index 46050b4..8972fdf 100644
--- a/block.c
+++ b/block.c
@@ -880,6 +880,35 @@ static int exec_mount(const char *source, const char *target,
 	return err;
 }
 
+static int hotplug_call_mount(const char *action, const char *device)
+{
+	pid_t pid;
+	int err;
+
+	pid = fork();
+	if (!pid) {
+		char * const argv[] = { "hotplug-call", "mount", NULL };
+
+		setenv("ACTION", action, 1);
+		setenv("DEVICE", device, 1);
+
+		execv("/sbin/hotplug-call", argv);
+		exit(-1);
+	} else if (pid > 0) {
+		int status;
+
+		pid = waitpid(pid, &status, 0);
+		if (pid <= 0 || !WIFEXITED(status) || WEXITSTATUS(status)) {
+			err = -ENOEXEC;
+			ULOG_ERR("hotplug-call call failed\n");
+		}
+	} else {
+		err = -errno;
+	}
+
+	return err;
+}
+
 static int handle_mount(const char *source, const char *target,
                         const char *fstype, struct mount *m)
 {
@@ -1079,6 +1108,8 @@ static int mount_device(struct probe_info *pr, int type)
 
 	handle_swapfiles(true);
 
+	hotplug_call_mount("add", device);
+
 	return 0;
 }
 
@@ -1091,6 +1122,8 @@ static int umount_device(char *path)
 	if (!mp)
 		return -1;
 
+	hotplug_call_mount("remove", basename(path));
+
 	err = umount2(mp, MNT_DETACH);
 	if (err)
 		ULOG_ERR("unmounting %s (%s) failed (%d) - %m\n", path, mp,
-- 
2.13.7


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