gistfile1.txt

fstools: use ramoverlay if no rootfs_data and rootfs is ro

- libfstools/mtd.c no longer fails if volume is ro.
- mount_root ramoverlay if no rootfs_data and rootfs is ro

Signed-off-by: Arvid E. Picciani <[email protected]>
---
 libfstools/mtd.c    | 35 ++++++++++++++++++++++-------------
 libfstools/volume.c | 24 ++++++++++++++++++++++++
 libfstools/volume.h |  1 +
 mount_root.c        | 11 +++++++++++
 4 files changed, 58 insertions(+), 13 deletions(-)

diff --git a/libfstools/mtd.c b/libfstools/mtd.c
index 77c71ee..4ff10ca 100644
--- a/libfstools/mtd.c
+++ b/libfstools/mtd.c
@@ -20,6 +20,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <mtd/mtd-user.h>
+#include <stdint.h>

 #include "libfstools.h"

@@ -32,15 +33,18 @@ struct mtd_volume {
        int     fd;
        int     idx;
        char    *chr;
+       int     is_writable;
 };

 static struct driver mtd_driver;

-static int mtd_open(const char *mtd, int block)
+static int mtd_open(const char *mtd, int block, int open_writable)
 {
        FILE *fp;
        char dev[PATH_MAX];
-       int i, ret, flags = O_RDWR | O_SYNC;
+       int i, ret, flags = O_SYNC;
+       if (open_writable)
+               flags |= O_RDWR;

        if ((fp = fopen("/proc/mtd", "r"))) {
                while (fgets(dev, sizeof(dev), fp)) {
@@ -70,24 +74,29 @@ static void mtd_volume_close(struct mtd_volume *p)
        p->fd = 0;
 }

-static int mtd_volume_load(struct mtd_volume *p)
+static int mtd_volume_load(struct mtd_volume *p,  int open_writable)
 {
        struct volume *v = &p->v;
        struct mtd_info_user mtdInfo;
        struct erase_info_user mtdLockInfo;

        if (p->fd) {
-               lseek(p->fd, 0, SEEK_SET);
-               return 0;
+               if (!open_writable || p->is_writable) {
+                       lseek(p->fd, 0, SEEK_SET);
+                       return 0;
+               } else {
+                       close(p->fd);
+                       p->fd = 0;
+               }
        }

        if (!p->chr)
                return -1;

-       p->fd = mtd_open(p->chr, 0);
+       p->fd = mtd_open(p->chr, 0, open_writable);
        if (p->fd < 0) {
                p->fd = 0;
-               ULOG_ERR("Could not open mtd device: %s\n", p->chr);
+               ULOG_ERR("Could not open mtd device%s: %s\n", open_writable ? " writable": "", p->chr);
                return -1;
        }

@@ -174,7 +183,7 @@ static struct volume *mtd_volume_find(char *name)
        snprintf(buffer, sizeof(buffer), "/dev/mtd%s", idx);
        p->chr = strdup(buffer);

-       if (mtd_volume_load(p)) {
+       if (mtd_volume_load(p, 0)) {
                ULOG_ERR("reading %s failed\n", v->name);
                free(p);
                return NULL;
@@ -190,7 +199,7 @@ static int mtd_volume_identify(struct volume *v)
        __u16 jffs2;
        size_t sz;

-       if (mtd_volume_load(p)) {
+       if (mtd_volume_load(p, 0)) {
                ULOG_ERR("reading %s failed\n", v->name);
                return -1;
        }
@@ -228,7 +237,7 @@ static int mtd_volume_erase(struct volume *v, int offset, int len)
        struct erase_info_user eiu;
        int first_block, num_blocks;

-       if (mtd_volume_load(p))
+       if (mtd_volume_load(p, 1))
                return -1;

        if (offset % v->block_size || len % v->block_size) {
@@ -270,7 +279,7 @@ static int mtd_volume_init(struct volume *v)
        struct mtd_info_user mtdinfo;
        int ret;

-       if (mtd_volume_load(p))
+       if (mtd_volume_load(p, 0))
                return -1;

        ret = ioctl(p->fd, MEMGETINFO, &mtdinfo);
@@ -291,7 +300,7 @@ static int mtd_volume_read(struct volume *v, void *buf, int offset, int length)
 {
        struct mtd_volume *p = container_of(v, struct mtd_volume, v);;

-       if (mtd_volume_load(p))
+       if (mtd_volume_load(p, 0))
                return -1;

        if (lseek(p->fd, offset, SEEK_SET) == (off_t) -1) {
@@ -311,7 +320,7 @@ static int mtd_volume_write(struct volume *v, void *buf, int offset, int length)
 {
        struct mtd_volume *p = container_of(v, struct mtd_volume, v);;

-       if (mtd_volume_load(p))
+       if (mtd_volume_load(p, 1))
                return -1;

        if (lseek(p->fd, offset, SEEK_SET) == (off_t) -1) {
diff --git a/libfstools/volume.c b/libfstools/volume.c
index 0d293d5..9b8a6af 100644
--- a/libfstools/volume.c
+++ b/libfstools/volume.c
@@ -14,6 +14,10 @@
 #include <sys/mount.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stropts.h>

 #include "libfstools.h"
 #include "volume.h"
@@ -41,3 +45,23 @@ struct volume* volume_find(char *name)

        return NULL;
 }
+
+int
+volume_is_ro(struct volume *v)
+{
+       if (!v || !v->blk)
+               return 0;
+
+       int flag = 0;
+       int fd = open(v->blk, O_RDONLY);
+
+       if (fd < 0)
+               return 0;
+
+       if (ioctl (fd, BLKROGET, &flag) == -1)
+               flag = 0;
+
+       close(fd);
+       return flag;
+}
+
diff --git a/libfstools/volume.h b/libfstools/volume.h
index 912b711..6460dad 100644
--- a/libfstools/volume.h
+++ b/libfstools/volume.h
@@ -62,6 +62,7 @@ struct volume {

 extern struct volume* volume_find(char *name);
 extern void volume_register_driver(struct driver *drv);
+extern int volume_is_ro(struct volume *v);

 static inline int volume_init(struct volume *v)
 {
diff --git a/mount_root.c b/mount_root.c
index dffb0a6..6dccf24 100644
--- a/mount_root.c
+++ b/mount_root.c
@@ -33,6 +33,7 @@ start(int argc, char *argv[1])
        struct volume *root;
        struct volume *data = volume_find("rootfs_data");
        struct stat s;
+       int overlay_from_ramfs = 0;

        if (!getenv("PREINIT") && stat("/tmp/.preinit", &s))
                return -1;
@@ -42,6 +43,11 @@ start(int argc, char *argv[1])
                volume_init(root);
                ULOG_NOTE("mounting /dev/root\n");
                mount("/dev/root", "/", NULL, MS_NOATIME | MS_REMOUNT, 0);
+
+               // if root is read only and there's no roofs_data, get an overlay from either extroot or ramfs
+               if (volume_is_ro(root)) {
+                       overlay_from_ramfs = 1;
+               }
        }

        /*
@@ -55,6 +61,11 @@ start(int argc, char *argv[1])
                return 0;
        }

+       if (overlay_from_ramfs) {
+               ULOG_WARN("no rootfs_data and rootfs is read only, using tmpfs overlay\n");
+               return ramoverlay();
+       }
+
        /* There isn't extroot, so just try to mount "rootfs_data" */
        volume_init(data);
        switch (volume_identify(data)) {