Version 22 will install and works on a WD N750. Unfortunately it is only a matter of time (a day to a few weeks) until the SquashFS corruption issue will appear and the router will ultimately become unstable and crash. This does not occur on 19.07.
More details here:
This is actually a solution
This is not an "issue" what I'm posting here, instead, it's a solution. A patch for the Linux kernel that might solve the SQUASHFS problem for some devices [don't expect this to be a magic solution if your hardware is actually faulty].
The background behind this research
I'm a developer, I started my journey by developing for AOSP when I was younger (like when I was 15 or 16). I may not be the smartest or the wiser, neither the more expert. However, I do have a stron…
opened 06:24PM - 20 Oct 21 UTC
kernel
target/ramips
release/21.02
flyspray
bug
release/22.03
*crowston:*
Supply the following if possible:
- Device problem occurs on
W… estern Digital My Net N750
- Software versions of OpenWrt/LEDE release, packages, etc.
openwrt-21.02.0
strongswan, dnscrypt-proxy2, avahi-utils, luci-app-ddns
- Steps to reproduce
I installed openwrt-21.02.0-ath79-generic-wd_mynet-n750-squashfs-sysupgrade.bin on a Western Digital My Net N750 that had been running openwrt-19.
The router seemed okay initially but after power cycling, it started reporting errors:
Oct 17 12:20:37 router2 kernel: [ 38.613970] SQUASHFS error: xz decompression failed, data probably corrupt
Oct 17 12:20:37 router2 kernel: [ 38.621029] SQUASHFS error: squashfs_read_data failed to read block 0x23686e
Oct 17 12:20:37 router2 kernel: [ 38.628199] SQUASHFS error: Unable to read fragment cache entry [23686e]
Oct 17 12:20:37 router2 kernel: [ 38.635010] SQUASHFS error: Unable to read page, block 23686e, size 16b28
The filesystem problem would leave some random file damaged, so different services would fail. Over time, the router became less and less functional as various files became inaccessible and after a few cycles, wouldn't boot at all.
I wondered if there was a problem with my old configuration on the new release (though I'm not sure how that could damage the squashfs), so I reinstalled a few more times in different ways, e.g., doing a factory install (openwrt-21.02.0-ath79-generic-wd_mynet-n750-squashfs-factory.bin and then the upgrade) instead of just the upgrade, and configuring from scratch rather than from the backup. But each time I had the same problem with the router.
It wasn't the same block on different installs, I noticed, but it seemed to be consistent for a particular installation attempt.
Oct 17 16:11:14 router2 kernel: [ 53.182571] SQUASHFS error: xz decompression failed, data probably corrupt
Oct 17 16:11:14 router2 kernel: [ 53.189582] SQUASHFS error: squashfs_read_data failed to read block 0x21e9e6
Oct 17 16:11:14 router2 kernel: [ 53.196749] SQUASHFS error: Unable to read fragment cache entry [21e9e6]
Oct 17 16:11:14 router2 kernel: [ 53.203559] SQUASHFS error: Unable to read page, block 21e9e6, size fd9c
Once there were two blocks (I think this is a reboot of the install above):
Oct 17 16:29:04 router2 kernel: [ 78.505075] SQUASHFS error: xz decompression failed, data probably corrupt
Oct 17 16:29:04 router2 kernel: [ 78.512103] SQUASHFS error: squashfs_read_data failed to read block 0x1e6e76
Oct 17 16:29:05 router2 kernel: [ 79.111366] SQUASHFS error: xz decompression failed, data probably corrupt
Oct 17 16:29:05 router2 kernel: [ 79.118386] SQUASHFS error: squashfs_read_data failed to read block 0x21e9e6
Oct 17 16:29:05 router2 kernel: [ 79.125565] SQUASHFS error: Unable to read fragment cache entry [21e9e6]
Oct 17 16:29:05 router2 kernel: [ 79.132445] SQUASHFS error: Unable to read page, block 21e9e6, size fd9c
One time there was first a jffs error, followed by lots of squashfs errors. Sorry, I don't have the log for that one.
I now realize that I should have tried power cycling a clean install a few times to see if there were errors right away or if they only happened after files were installed/changed.
To check whether the router was just having a hardware problem, I reinstalled openwrt-19.07.8 and configured it the same. I have not seen any errors after a few power cycles, which points to a problem with the new release. I did not see any bug reports on this tracker that mention squashfs problems and googling, I did not find any useful discussions, hence this bug report.
I guess it could be that the new release uses a bad bit of memory that the earlier release managed to miss. I looked for but didn't find a memory test utility, so I don't know how to examine that possibility. Though the fact that it was different blocks each time makes it not sound like a hardware problem.