[OpenWrt-Devel] [PATCH fstools] blockd: use uloop_process for calling /sbin/hotplug-call mount
Rafał Miłecki
zajec5 at gmail.com
Tue May 5 15:26:32 EDT 2020
From: Rafał Miłecki <rafal at milecki.pl>
As blockd uses uloop calling any script and using waitpid() can easily
result in a lock. It's enough for script to use /bin/ubus to cause that.
It's not an option to drop waitpid() as it's important to e.g. call
mount scripts with ACTION=remove before unmounting devices. So solving
this problem requires using uloop_process.
Unfortunately this means:
1. Using callbacks making code slightly more complex
2. Dropping that nice devices_update_cb()
With this change however hotplug.d "mount" scripts can safely call
"ubus".
Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
block.c | 4 --
blockd.c | 127 +++++++++++++++++++++++++++++++++++--------------------
2 files changed, 80 insertions(+), 51 deletions(-)
diff --git a/block.c b/block.c
index c4ae88a..ac95464 100644
--- a/block.c
+++ b/block.c
@@ -1218,10 +1218,6 @@ static int main_autofs(int argc, char **argv)
blockd_notify(pr->dev, m, pr);
}
- } else if (!strcmp(argv[2], "available")) {
- err = hotplug_call_mount("add", argv[3]);
- } else if (!strcmp(argv[2], "unavailable")) {
- err = hotplug_call_mount("remove", argv[3]);
} else {
if (argc < 4)
return -EINVAL;
diff --git a/blockd.c b/blockd.c
index 6e53a13..2fc1bb6 100644
--- a/blockd.c
+++ b/blockd.c
@@ -25,6 +25,11 @@
#define AUTOFS_TIMEOUT 30
#define AUTOFS_EXPIRE_TIMER (5 * 1000)
+struct hotplug_context {
+ struct uloop_process process;
+ struct device *device;
+};
+
struct device {
struct vlist_node node;
struct blob_attr *msg;
@@ -108,15 +113,49 @@ block(char *cmd, char *action, char *device)
return ret;
}
-static void
-device_free(struct device *device)
+static void hotplug_call_mount(const char *action, struct device *device,
+ uloop_process_handler cb)
{
- char *mp;
+ char * const argv[] = { "hotplug-call", "mount", NULL };
+ struct hotplug_context *c = NULL;
+ pid_t pid;
- if (!device->autofs)
- return;
+ if (cb) {
+ c = calloc(1, sizeof(*c));
+ if (!c)
+ return;
+ }
+
+ pid = fork();
+ switch (pid) {
+ case -1:
+ ULOG_ERR("fork() failed\n");
+ break;
+ case 0:
+ uloop_end();
+
+ setenv("ACTION", action, 1);
+ setenv("DEVICE", device->name, 1);
+
+ execv("/sbin/hotplug-call", argv);
+ exit(-1);
+ break;
+ default:
+ if (c) {
+ c->process.pid = pid;
+ c->process.cb = cb;
+ c->device = device;
+ uloop_process_add(&c->process);
+ }
+ break;
+ }
+}
- block("autofs", "unavailable", device->name);
+static void device_mount_remove_hotplug_cb(struct uloop_process *p, int stat)
+{
+ struct hotplug_context *c = container_of(p, struct hotplug_context, process);
+ struct device *device = c->device;
+ char *mp;
if (device->target)
unlink(device->target);
@@ -126,17 +165,21 @@ device_free(struct device *device)
block("autofs", "remove", device->name);
free(mp);
}
+
+ free(device);
+ free(c);
}
-static void
-device_add(struct device *device)
+static void device_mount_remove(struct device *device)
+{
+ hotplug_call_mount("remove", device, device_mount_remove_hotplug_cb);
+}
+
+static void device_mount_add(struct device *device)
{
struct stat st;
char path[64];
- if (!device->autofs)
- return;
-
snprintf(path, sizeof(path), "/tmp/run/blockd/%s", device->name);
if (!lstat(device->target, &st)) {
if (S_ISLNK(st.st_mode))
@@ -147,7 +190,7 @@ device_add(struct device *device)
if (symlink(path, device->target))
ULOG_ERR("failed to symlink %s->%s (%d) - %m\n", device->target, path, errno);
else
- block("autofs", "available", device->name);
+ hotplug_call_mount("add", device, NULL);
}
static int
@@ -177,36 +220,13 @@ device_move(struct device *device_o, struct device *device_n)
return 0;
}
-static void
-devices_update_cb(struct vlist_tree *tree, struct vlist_node *node_new,
- struct vlist_node *node_old)
+static void vlist_nop_update(struct vlist_tree *tree,
+ struct vlist_node *node_new,
+ struct vlist_node *node_old)
{
- struct device *device_o = NULL, *device_n = NULL;
-
- if (node_old)
- device_o = container_of(node_old, struct device, node);
-
- if (node_new)
- device_n = container_of(node_new, struct device, node);
-
- if (device_o && device_n) {
- if (device_move(device_o, device_n)) {
- device_free(device_o);
- device_add(device_n);
- if (!device_n->autofs)
- block("mount", NULL, NULL);
- }
- } else if (device_n) {
- device_add(device_n);
- } else {
- device_free(device_o);
- }
-
- if (device_o)
- free(device_o);
}
-VLIST_TREE(devices, avl_strcmp, devices_update_cb, false, false);
+VLIST_TREE(devices, avl_strcmp, vlist_nop_update, false, false);
static int
block_hotplug(struct ubus_context *ctx, struct ubus_object *obj,
@@ -246,22 +266,35 @@ block_hotplug(struct ubus_context *ctx, struct ubus_object *obj,
if (data[MOUNT_REMOVE]) {
vlist_delete(&devices, &device->node);
- } else {
- if (data[MOUNT_AUTOFS])
- device->autofs = blobmsg_get_u32(data[MOUNT_AUTOFS]);
- else
- device->autofs = 0;
- if (data[MOUNT_ANON])
- device->anon = blobmsg_get_u32(data[MOUNT_ANON]);
+
+ if (device->autofs)
+ device_mount_remove(device);
else
- device->anon = 0;
+ free(device);
+ } else {
+ struct device *old = vlist_find(&devices, devname, device, node);
+
+ device->autofs = data[MOUNT_AUTOFS] ? blobmsg_get_u32(data[MOUNT_AUTOFS]) : 0;
+ device->anon = data[MOUNT_ANON] ? blobmsg_get_u32(data[MOUNT_ANON]) : 0;
device->msg = _msg;
memcpy(_msg, msg, blob_raw_len(msg));
device->name = _name;
strcpy(_name, devname);
device->target = __target;
strcpy(__target, target);
+
vlist_add(&devices, &device->node, device->name);
+
+ if (old && !device_move(old, device)) {
+ if (device->autofs) {
+ device_mount_remove(old);
+ device_mount_add(device);
+ } else {
+ block("mount", NULL, NULL);
+ }
+ } else if (device->autofs) {
+ device_mount_add(device);
+ }
}
return 0;
--
2.26.1
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