Re: [RAUC] Failed to mount seed slot

[Ladislav Michl <ladis@linux-mips.org>]

On Tue, May 07, 2019 at 09:31:28AM +0200, Ladislav Michl wrote:
> On Mon, May 06, 2019 at 07:44:09PM +0200, Ladislav Michl wrote:
> > Hi there,
> > 
> > I'm using rauc with casync to update target system - it is symmetric rootfsA,
> > rootfsB, scenario, so slots are defined as:
> > [slot.rootfs.0]
> > device=/dev/ubi0_0
> > type=ubifs
> > bootname=system0
> > 
> > [slot.rootfs.1]
> > device=/dev/ubi0_1
> > type=ubifs
> > bootname=system1
> > 
> > Now system is booted with rootfs mounted read only which makes mounting seed
> > slot fail:
> > rauc[871]: Mounting /dev/ubi0_0 to use as seed
> > rauc[871]: launching subprocess: mount -t ubifs /dev/ubi0_0 /run/rauc/rootfs.0
> > rauc[871]: posix_spawn avoided (fd close requested) (child_setup specified) 
> > rauc[871]: mount: /run/rauc/rootfs.0: /dev/ubi0_0 already mounted or mount point busy.
> > 
> > Here adding '-o ro' would quick fix it up (but break rw case, as options have to
> > match), so it seems better to use bind mount as comment casync_extract_image
> > function suggests, but do not see it code.
> > 
> > Am I missing anything?
> 
> So, whats still missing is a review of pull request #406 (Normalize device names
> to find mounted slots) :)

It feels really strange talking to myself, so let's hope someone else joins as
well, hence Cc list.

Problem is similar to that one solved by #406 and #388, however it needs to be
extended to ubi<X> and possibly mtd<X> case. For now let's start with fixing
pull request #406 to:
- use C comments
- avoid unneded allocations
- also allow character devices (for example /dev/ubi0_0)

> Then determine_slot_states should properly fill slot's ext_mount_point and
> casync_extract_image would then use it to bind mount seed slot.
> 
> And here's the tricky part. For device-less mount, volume to mount is specified
> for example using ubiX_Y or ubiX:NAME syntax, so fix in #406 will fail in this
> case.

This one was fixed by extending normalize_mountable_object from #406 and
adjusting casync_extract_image, but lets first get #406 revieved and merged :)
Trent, in case you want to merge following additional patch to your PR here's my
Signed-off-by: Ladislav Michl <ladis@linux-mips.org>

diff --git a/src/config_file.c b/src/config_file.c
index 875e0ee..e592d15 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -494,27 +494,25 @@ free:
 	return res;
 }
 
-// Something that is, or can be, mounted onto a mount point
+/* Something that is, or can be, mounted onto a mount point */
 typedef struct {
-	gboolean is_device;  // vs being a loop mounted file
-	dev_t dev;  // the device, or for a file, the device the file is on
-	ino_t inode;  // inode of file for a non-device
+	gboolean is_device;	/* vs being a loop mounted file */
+	dev_t dev;		/* the device, or for a file, the device the file is on */
+	ino_t inode;		/* inode of file for a non-device */
 } MountableObj;
 
-// Take a device (or file) path and normalize it
-static MountableObj *normalize_mountable_object(const gchar *devicepath)
+/* Take a device (or file) path or name and normalize it */
+static gboolean normalize_mountable_object(const gchar *devicename, MountableObj *obj)
 {
-	MountableObj *obj;
 	GStatBuf st;
 
-	if (g_stat(devicepath, &st) == -1) {
+	if (g_stat(devicename, &st) == -1) {
 		/* Virtual filesystems like devpts trigger case */
-		g_debug("Can't stat '%s', assuming unmountable: %s", devicepath, g_strerror(errno));
-		return NULL;
+		g_debug("Can't stat '%s', assuming unmountable: %s", devicename, g_strerror(errno));
+		return FALSE;
 	}
 
-	obj = g_new0(MountableObj, 1);
-	if (S_ISBLK(st.st_mode)) {
+	if (S_ISBLK(st.st_mode) || S_ISCHR(st.st_mode)) {
 		obj->is_device = TRUE;
 		obj->dev = st.st_rdev;
 	} else if (S_ISREG(st.st_mode)) {
@@ -522,10 +520,10 @@ static MountableObj *normalize_mountable_object(const gchar *devicepath)
 		obj->dev = st.st_dev;
 		obj->inode = st.st_ino;
 	} else {
-		g_debug("Device '%s' is not something which is mountable", devicepath);
-		g_clear_pointer(&obj, g_free);
+		g_debug("Device '%s' is not something which is mountable", devicename);
+		return FALSE;
 	}
-	return obj;
+	return TRUE;
 }
 
 /* Compare two MountableObj for equality */
@@ -546,24 +544,24 @@ RaucSlot *find_slot_by_device(GHashTable *slots, const gchar *device)
 {
 	GHashTableIter iter;
 	RaucSlot *slot;
-	g_autofree MountableObj *obj = NULL;
+	MountableObj obj;
+	gboolean normalized;
 
 	g_return_val_if_fail(slots, NULL);
 	g_return_val_if_fail(device, NULL);
 
-	obj = normalize_mountable_object(device);
+	normalized = normalize_mountable_object(device, &obj);
 
 	g_hash_table_iter_init(&iter, slots);
 	while (g_hash_table_iter_next(&iter, NULL, (gpointer*) &slot)) {
 		if (g_strcmp0(slot->device, device) == 0)
 			goto out;
 
-		// Path doesn't match, but maybe device is same?
-		if (obj) {
-			g_autofree MountableObj *slot_obj =
-				normalize_mountable_object(slot->device);
-
-			if (slot_obj && is_same_mountable_object(obj, slot_obj))
+		/* Path doesn't match, but maybe device is the same? */
+		if (normalized) {
+			MountableObj slot_obj;
+			if (normalize_mountable_object(slot->device, &slot_obj) &&
+			    is_same_mountable_object(&obj, &slot_obj))
 				goto out;
 		}
 	}