document mount_root and block (extroot) a bit

Also s/fs_data/blkdev_path/ which should make more sense.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

diff --git a/block.c b/block.c
index 6d187d1..bba68c2 100644 (file)
--- a/block.c
+++ b/block.c
@@ -935,6 +935,9 @@ static int check_extroot(char *path)
        return -1;
 }
 
+/*
+ * Read info about extroot from UCI (using prefix) and mount it.
+ */
 static int mount_extroot(char *cfg)
 {
        char overlay[] = "/tmp/extroot/overlay";
@@ -944,9 +947,11 @@ static int mount_extroot(char *cfg)
        struct mount *m;
        int err = -1;
 
+       /* Load @cfg/etc/config/fstab */
        if (config_load(cfg))
                return -2;
 
+       /* See if there is extroot-specific mount config */
        m = find_block(NULL, NULL, NULL, "/");
        if (!m)
                m = find_block(NULL, NULL, NULL, "/overlay");
@@ -957,6 +962,7 @@ static int mount_extroot(char *cfg)
                return -1;
        }
 
+       /* Find block device pointed by the mount config */
        pr = find_block_info(m->uuid, m->label, m->device);
 
        if (!pr && delay_root){
@@ -999,7 +1005,7 @@ static int main_extroot(int argc, char **argv)
 {
        struct blkid_struct_probe *pr;
        char fs[32] = { 0 };
-       char fs_data[32] = { 0 };
+       char blkdev_path[32] = { 0 };
        int err = -1;
 #ifdef UBIFS_EXTROOT
        libubi_t libubi;
@@ -1016,6 +1022,10 @@ static int main_extroot(int argc, char **argv)
        mkblkdev();
        cache_load(1);
 
+       /*
+        * Make sure there is "rootfs" MTD partition or UBI volume.
+        * TODO: What for?
+        */
        find_block_mtd("rootfs", fs, sizeof(fs));
        if (!fs[0]) {
 #ifdef UBIFS_EXTROOT
@@ -1038,14 +1048,24 @@ static int main_extroot(int argc, char **argv)
                return -3;
        }
 
-       find_block_mtd("rootfs_data", fs_data, sizeof(fs_data));
-       if (fs_data[0]) {
-               pr = find_block_info(NULL, NULL, fs_data);
+       /*
+        * Look for "rootfs_data". We will want to mount it and check for
+        * extroot configuration.
+        */
+
+       /* Start with looking for MTD partition */
+       find_block_mtd("rootfs_data", blkdev_path, sizeof(blkdev_path));
+       if (blkdev_path[0]) {
+               pr = find_block_info(NULL, NULL, blkdev_path);
                if (pr && !strcmp(pr->id->name, "jffs2")) {
                        char cfg[] = "/tmp/jffs_cfg";
 
+                       /*
+                        * Mount MTD part and try extroot (using
+                        * /etc/config/fstab from that partition)
+                        */
                        mkdir_p(cfg);
-                       if (!mount(fs_data, cfg, "jffs2", MS_NOATIME, NULL)) {
+                       if (!mount(blkdev_path, cfg, "jffs2", MS_NOATIME, NULL)) {
                                err = mount_extroot(cfg);
                                umount2(cfg, MNT_DETACH);
                        }
@@ -1057,15 +1077,17 @@ static int main_extroot(int argc, char **argv)
        }
 
 #ifdef UBIFS_EXTROOT
-       memset(fs_data, 0, sizeof(fs_data));
+       /* ... but it also could be an UBI volume */
+       memset(blkdev_path, 0, sizeof(blkdev_path));
        libubi = libubi_open();
-       find_block_ubi(libubi, "rootfs_data", fs_data, sizeof(fs_data));
+       find_block_ubi(libubi, "rootfs_data", blkdev_path, sizeof(blkdev_path));
        libubi_close(libubi);
-       if (fs_data[0]) {
+       if (blkdev_path[0]) {
                char cfg[] = "/tmp/ubifs_cfg";
 
+               /* Mount volume and try extroot (using fstab from that vol) */
                mkdir_p(cfg);
-               if (!mount(fs_data, cfg, "ubifs", MS_NOATIME, NULL)) {
+               if (!mount(blkdev_path, cfg, "ubifs", MS_NOATIME, NULL)) {
                        err = mount_extroot(cfg);
                        umount2(cfg, MNT_DETACH);
                }

diff --git a/libfstools/extroot.c b/libfstools/extroot.c
index 9a05c49..45cc3f5 100644 (file)
--- a/libfstools/extroot.c
+++ b/libfstools/extroot.c
@@ -24,6 +24,10 @@
 
 char const *extroot_prefix = NULL;
 
+/*
+ * This will execute "block extroot" and make use of mounted extroot or return
+ * an error.
+ */
 int mount_extroot(void)
 {
        char ldlib_path[32];

diff --git a/mount_root.c b/mount_root.c
index c1524a4..a8505fa 100644 (file)
--- a/mount_root.c
+++ b/mount_root.c
@@ -18,6 +18,10 @@
 #include "libfstools/libfstools.h"
 #include "libfstools/volume.h"
 
+/*
+ * Called in the early (PREINIT) stage, when we immediately need some writable
+ * filesystem.
+ */
 static int
 start(int argc, char *argv[1])
 {
@@ -34,15 +38,26 @@ start(int argc, char *argv[1])
                return 0;
        }
 
+       /*
+        * Before trying to mount and use "rootfs_data" let's check if there is
+        * extroot configured. Following call will handle reading config from
+        * the "rootfs_data" on its own.
+        */
        extroot_prefix = "";
        if (!mount_extroot()) {
                fprintf(stderr, "fs-state: switched to extroot\n");
                return 0;
        }
 
+       /* There isn't extroot, so just try to mount "rootfs_data" */
        switch (volume_identify(v)) {
        case FS_NONE:
        case FS_DEADCODE:
+               /*
+                * Filesystem isn't ready yet and we are in the preinit, so we
+                * can't afford waiting for it. Use tmpfs for now and handle it
+                * properly in the "done" call.
+                */
                return ramoverlay();
 
        case FS_JFFS2:
@@ -67,6 +82,9 @@ stop(int argc, char *argv[1])
        return 0;
 }
 
+/*
+ * Called at the end of init, it can wait for filesystem if needed.
+ */
 static int
 done(int argc, char *argv[1])
 {