libfstools/mtd: attempt to read from OOB data if empty space is found

When using jffs2 on NAND flash, it stores its magic in the OOB data on
newly erased blocks. This change fixes identifying the filesystem type.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/libfstools/mtd.c b/libfstools/mtd.c
index 77c71eeb29a3ba7a67c42514b5e17e324baf53d4..c5dce500c20283f5610b198d2b63a90e1a641893 100644 (file)
--- a/libfstools/mtd.c
+++ b/libfstools/mtd.c
@@ -187,7 +187,6 @@ static int mtd_volume_identify(struct volume *v)
 {
        struct mtd_volume *p = container_of(v, struct mtd_volume, v);;
        __u32 deadc0de;
-       __u16 jffs2;
        size_t sz;
 
        if (mtd_volume_load(p)) {
@@ -202,6 +201,16 @@ static int mtd_volume_identify(struct volume *v)
                return -1;
        }
 
+       if (deadc0de == ~0) {
+               struct mtd_oob_buf oob = {
+                       .start = 0,
+                       .length = sizeof(deadc0de),
+                       .ptr = (void *)&deadc0de,
+               };
+
+               ioctl(p->fd, MEMREADOOB, &oob);
+       }
+
        if (deadc0de == __be32_to_cpu(0x4f575254))
                return FS_SNAPSHOT;
 
@@ -210,10 +219,9 @@ static int mtd_volume_identify(struct volume *v)
                return FS_DEADCODE;
        }
 
-       jffs2 = __be16_to_cpu(deadc0de >> 16);
-       if (jffs2 == 0x1985) {
+       if (__be16_to_cpu(deadc0de) == 0x1985 ||
+           __be16_to_cpu(deadc0de >> 16) == 0x1985)
                return FS_JFFS2;
-       }
 
        if (v->type == UBIVOLUME && deadc0de == 0xffffffff) {
                return FS_JFFS2;