[OpenWrt-Devel] [PATCH v2] fstools: Add support to read-only MTD partitions (eg. recovery images)

[Daniel Golle]

Hi Bruno,
Hi Steve,

On Tue, Jan 21, 2020 at 11:24:28AM +0100, Bruno Pena wrote:
> Please also include the contents of "dmesg" and of the files
> "/proc/cmdline" and "/proc/mtd".
> 
> Best regards,
> Bruno Pena
> 
> On Tue, Jan 21, 2020, 11:01 Bruno Pena <brunompena at gmail.com> wrote:
> 
> > Hi Steve,
> >
> > These patches should only impact partitions that are marked as read only.
> > Can you please provide more details about your configuration?
> > (architecture, device profile, mtd layout, the mtd partition generating the
> > error)

I think this is because opening /dev/mtdX will fail as read-write
but will succeed in read-only mode. Hence /dev/mtdblockX is not even
considered which is a change from the previous behaviour.

> >
> > Best regards,
> > Bruno Pena
> >
> > On Tue, Jan 21, 2020, 10:51 Steve Brown <sbrown at ewol.com> wrote:
> >
> >> Hi Bruno,
> >>
> >> On Sat, 2020-01-04 at 12:52 +0100, Bruno Pena wrote:
> >> > This patch enables fstools to open read-only MTD partitions, which in
> >> > turn also enables OpenWrt to boot from read-only partitions.
> >> >
> >> > The use of read-only partitions is of special importance for WiFi-
> >> > only
> >> > devices, where a protected read-only recovery image can be used in
> >> > case
> >> > something goes wrong with the main firmware (eg. user gets locked out
> >> > due to bad settings, flash of an unbootable dev firmware, etc).
> >> >
> >> > Signed-off-by: Bruno Pena <brunompena at gmail.com>
> >> > ---
> >> >  libfstools/mtd.c | 19 +++++++++++++++----
> >> >  1 file changed, 15 insertions(+), 4 deletions(-)
> >> >
> >> > diff --git a/libfstools/mtd.c b/libfstools/mtd.c
> >> > index 77c71ee..aae633e 100644
> >> > --- a/libfstools/mtd.c
> >> > +++ b/libfstools/mtd.c
> >> > @@ -36,20 +36,31 @@ struct mtd_volume {
> >> >
> >> >  static struct driver mtd_driver;
> >> >
> >> > +static int mtd_open_device(const char *dev)
> >> > +{
> >> > +     int ret;
> >> > +
> >> > +     ret = open(dev, O_RDWR | O_SYNC);
> >> > +     if (ret < 0)
> >> > +             ret = open(dev, O_RDONLY);
> >> > +
> >> > +     return ret;
> >> > +}
> >> > +
> >> >  static int mtd_open(const char *mtd, int block)
> >> >  {
> >> >       FILE *fp;
> >> >       char dev[PATH_MAX];
> >> > -     int i, ret, flags = O_RDWR | O_SYNC;
> >> > +     int i, ret;
> >> >
> >> >       if ((fp = fopen("/proc/mtd", "r"))) {
> >> >               while (fgets(dev, sizeof(dev), fp)) {
> >> >                       if (sscanf(dev, "mtd%d:", &i) && strstr(dev,
> >> > mtd)) {
> >> >                               snprintf(dev, sizeof(dev),
> >> > "/dev/mtd%s/%d", (block ? "block" : ""), i);
> >> > -                             ret = open(dev, flags);
> >> > +                             ret = mtd_open_device(dev);
> >> >                               if (ret < 0) {
> >> >                                       snprintf(dev, sizeof(dev),
> >> > "/dev/mtd%s%d", (block ? "block" : ""), i);
> >> > -                                     ret = open(dev, flags);
> >> > +                                     ret = mtd_open_device(dev);
> >> >                               }
> >> >                               fclose(fp);
> >> >                               return ret;
> >> > @@ -58,7 +69,7 @@ static int mtd_open(const char *mtd, int block)
> >> >               fclose(fp);
> >> >       }
> >> >
> >> > -     return open(mtd, flags);
> >> > +     return mtd_open_device(mtd);
> >> >  }
> >> >
> >> >  static void mtd_volume_close(struct mtd_volume *p)
> >>
> >>
> >> This patch and related commit de80424f706682e8bba27c60bcd2a9c1b4a5e875
> >> break the jffs erase on my Archer a7 v5.
> >>
> >>     [   11.787856] jffs2_scan_eraseblock(): End of filesystem marker
> >> found at 0x10000
> >>     [   11.795357] jffs2_build_filesystem(): unlocking the mtd device...
> >>     [   11.795390] done.
> >>     [   11.803771] jffs2_build_filesystem(): erasing all blocks after the
> >> end marker...
> >>     [   11.803781] jffs2: Erase at 0x009e0000 failed immediately: -EROFS.
> >> Is the sector locked?
> >>          -------------
> >>     [   13.138841] jffs2: Erase at 0x00010000 failed immediately: -EROFS.
> >> Is the sector locked?
> >>     [   13.147188] done.
> >>     [   13.149202] jffs2: notice: (487) jffs2_build_xattr_subsystem:
> >> complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and
> >> 0 of xref (0 .
> >>     [   13.165896] mount_root: unable to set filesystem state
> >>     [   13.171443] mount_root: switching to jffs2 overlay
> >>     [   13.201867] overlayfs: failed to resolve '/overlay/upper': -2
> >>     [   13.223939] mount_root: mount failed:
> >> lowerdir=/,upperdir=/overlay/upper,workdir=/overlay/work, options No such
> >> device
> >>     [   13.235145] mount_root: switching to jffs2 failed - fallback to
> >> ramoverlay
> >>
> >> Verified by reverting de80424f7.
> >>
> >> Steve
> >>
> >>
> >>

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