Must have been readback failure in SP Flash Tool. Thanks Alecxs for advice on using mtkclient. Worked perfectly. All partitions normal. Super is 4 GB, as expected, boot also normal. Rooting worked. Thanks for help, both of you.

PowerIso can open the Android image files. https://www.poweriso.com/

Yes, each ROM has its own boot unless the ROM is explicitly build keeping the stock kernel. SO to able to boot your device again, unzip your PixelExperience ROM file, take boot.img from it and flash that.

The problem with /data has now been fixed. I had forgotten that in the past, I was trying the OrangeFox dual-boot recovery on this device, and it had repartitioned /data. I fixed this by flashing the appropriate *.img files again for my OS (OOS 10.3.8), and then by booting into the standard OrangeFox recovery (the non-dual-boot version) via fastboot, and then by using its adb sideload facility to flash that same OrangeFox recovery. OrangeFox's adb sideload mechanism offers options to the user for repartitioning and rebuilding /data. I utilized those options and set /data back to "Stock", and after that, /data became accessible again, and I could format it and access it in recovery with no problem. At this point, I flashed OOS 10.3.8, and I then flashed the appropriate TWRP and Magisk. Now, my device is back up and running in that OOS version. The EDL problem continues, but given that my device is now usable again, I am not overly concerned about this MsmDownloadTool issue at the moment. In my spare time, I'll continue to look into that. All's well that ends well! ... and now it's indeed a happy New Year for me!

This doesn't directly explain what you are seeing, but you have a missing step, which may possibly be contributing to your partitions getting reset by TWRP or something else. When you create a partition with parted, and include a partition type such as ext4, that doesn't actually make a file system on your new partition. To do that, you need to exit parted and format the partition using mkfs.ext4 /dev/block/mmcblk0p26 where 26 is the partition number of your cache, so repeat the same command using p27 and p28 for your other two partitions. If you don't have mkfs.ext4 there's a zipfile containing it along with parted and other related tools attached to https://forum.xda-developers.com/t/how-to-boot-from-sd-card-successfully-on-qmobile-z8-with-bricked-dead-emmc.3712171/ in the XDA Developer forum. There are zipfiles for both ARM and ARM64/AARCH builds, so choose whichever zipfile's right for your device.

Found them! All the missing partitions are listed with their labels in /dev/block/mapper

The newly flashed ROM was xiaomi.eu 12.0.4. I then tried various modifications of it, but all of them expose the same issue over and over again. After I flashed Lineage OS, the behavior was as expected: no way to see any files on "Internal Storage" (/sdcard or /data/media/0). In fact, as I expected in my original post, even though /sdcard is viewable in OrangeFox, the only directory there is Fox, where it puts recovery logs and other volatile data, but there are no files from user even visible whatsoever. Accordingly the "Data" partition is not even treated as mounted, and going to "Mount" option reveals that the checkbox of it is unchecked and one cannot even check it until one explicitly decrypts it. Interestingly, I would have expected such mount-related behavior only with FDE, but I can confirm that this installation has FBE. So this looks good now, but it's a pity that latest MIUI ROMs are that broken, what a mess... :(

Highly doubt if this can be done, even if it is feasible, it is extremely risky and could render the phone bricked! Some handsets have the capability to resize the partitions used. For example: The Zte Blade is one very good example that can enable through what's known as TPT transfer, where the /system, /cache and /data can be resized conveniently, albeit in a limited fixed way, such as 2Mb /cache, and 210Mb /system. See this example of the alternative layouts that can be used for this handset. The software used to achieve this, is not easy to find on the internet, known as, testpoint, although it does require specialized knowledge on how to use it, and does involve the risk of overwriting the IMEI number for this to work. There is one for Qualcomm based handsets and is floating around on the internet. Now, going back to T-Mobile Concord handset, not sure if there's one for specified handset concerned, as GSMArena indicates that this is a Broadcom chipset... It might be best to dig around on XDA to see if anyone has achieved it. If not, then take it as a no-go!

Primary reasons for the no swap recommendations are the basic uselessness of swap for most devices, performance reasons, and device longevity. As Liam mentions, modern devices have no shortage of RAM (Even my old underpowered Wildfire S has as much RAM as my previous desktop.) and that RAM is managed fairly well by the modern Android system, making a swap largely pointless. Also, even though flash is far better than platters of spinning rust, it's still orders of magnitude slower than RAM is, hence for performance reasons, you don't want to tier down to flash if you can at all avoid it. Furthermore, flash memory has a limit on how many times you can erase and rewrite it. While this cycle limit is typically in the thousands or tens of thousands, which combined with modern wear leveling systems, means you're unlikely to hit the limit within the useful lifespan of the device, but if you're using it as swap, with loads and loads of itty-bity writes, you will chew through those cycles needlessly and might actually bump against those limits in time.

If you use recovery to wipe user data, and then wipe your dalvik cache in the advanced settings, then reboot all apps and data will be removed. Ensure you haven't enabled google restore - when the startup wizard starts, it should ask if you want to restore to this device. Unstick this option.

A possible solution is described e.g. in this modaco forum thread. In case of that user, the sd-ext partition got corrupted as it was mounted wrongly by the Android system (he used GPartEd to create his partitions which, regardless of the filesystem created (ext2/3/4, fat32), then were mounted as ext4). So what he basically did: He factory reset the phone, deleted the partitions on SDCard, recreated them on phone (i.e. not with the card mounted to any PC, but directly on the phone, using CWMs options as far as I understood). I didn't try that solution myself, as I'm not affected by the problem.

Make sure you're making the second partition primary. Both partitions need to be primary, just because it's the second one it still is primary.

I fixed it by creating the sd-ext partition as another primary partition. Works fine now. I hope this helps somebody.

Who or how it was fixed as 190MB? The manufacturers decided that. They probably expected that that size would be sufficient during the expected time they will continue official support for the phone. Can the size of partition be increased? If you're rooted and installed custom boot loader, yes partitions can be resized, although not in a way that will satisfy everyone since it takes space away from internal memory and many people also have exhausted their internal space; it involves a lot of work to test and debug and since P500 has very little internal memory as well, at some point developers had to decide that it's just not worth the effort. I tried a tool but did not help. After all the process completed without any errors, I still see no change in the size. Are there any other ways to do it? What did you try? Hephappy, a ROM developer had commented in XDA page as "No space: P500 has 190MB for system partition." and hence he withdraws the plan of developing JB ROM for P500. Is it then a hardware limitation? Pretty much. All newer phones comes with much larger internal memory, you should consider an upgrade if you really wanted JB.

FYI The CyanogenMod 10 is the first update with the code to detect an invalid IMEI. You could already have an invalid IMEI and don't know about it. The issue with an invalid IMEI is that you may have emergency calling problems (inability to do emergency calls). Confirm IMEI Does the IMEI reported match the number under your battery? Dial *#06# and the IMEI will be presented on your screen. Possible Solution From this code.google.com thread, the user at comment 5 managed to solve the issue: Steps I took to solve the problem: Flash my phone by Odin to version 2.2.1 Update to CM9 using Recovery with stabile version od CM9 http://download.cyanogenmod.com/get/jenkins/5805/cm-9.0.0-galaxysmtd.zip Update to CM10 using last version of kernel. I used cm-10-20120822-NIGHTLY-galaxysmtd. Between steps I did wipe data/factory reset and wipe cache partition. Now my IMEI is correct. After cleaning the phone and updates do CM10 I recommend installing gapps-jb-20120726-signed, because your phone will be clean as a baby after birth.

I found another solution: Have a look at /data/system/uiderrors.txt. There you will find the apps that are responsible for the trouble. You can delete them (manualy if necessary) to fix the issue. Reinstalling the apps brings the error back, though.

I think your build f MIUI doesnt have the code for mounting the SD-ext partition on boot. To check this, open the init.d folder in your new ROM and see if it has any file relating to Sd-ext. This link has a init.d script for mounting the SD-ext partition link

According to this linky here this is what it has to say What is EFS? It is a place that stores your Android smartphone important data like Wi-Fi, Bluetooth MAC address and IMEI (nv_data.bin). After reading the above linky, it would be prudent to make a backup of that partition otherwise well and truly hosed! As for /firmware I am guessing that is where the original stock firmware goes into when updating via the official route a lá Kies. If anyone has a better insight feel free to comment, and I will gladly amend this accordingly

I think this post provides some information about it. It also seems to be consistent with what I've tried. Instead of partitioning the SD card, mounting an .img with a ext4 filesystem is a simple workaround.

There are two ways to apply and use swap on your device, using a swap file or using a swap partition. This guide provides instructions for both of them. Disable Compcache First step is to confirm the status or presence of the compressed cache, thus ensuring that it is disabled. While CyanogenMod does not enable Compcache support on all devices, and by default if available it comes disabled, you can check the status by accessing: Settings » CyanogenMod settings » Performance settings » Compcache If it doesn't show, your device doesn't support Compcache. If it show, disable it to use swap instead. Using swap (file or partition) Swap can give more available memory than Compcache, but you need at least a class 6 SD card to prevent slow access times. You should also be aware that SD write wear is increased, so, the card will last less than usual would last. Using a swap file This is the easiest way, you can have an app creating and managing the swap file for you: Here's three recommended apps for this: Swapper 2 Swapper DroidSwap Using a swap partition You can manually create a swap partition, but for that to happen, you need to backup your SD card contents; format, and partition it. The swap partition does bring better compatibility, when compared with swap files, but only concerning the connection of your phone as an USB mass storage device. SD card partitioning The method of reference if the use of MiniTool Partition Wizard Home Edition, compatible with Windows 2000/XP/Vista & Windows 7. Download and install MiniTool Partition Wizard; Remove the SD card from your device, insert into USB SD Card reader. Windows should report a new drive and you should see the drive contents. Delete old partitions on SD card: Notes: Operations are QUEUED, not instantly applied. So nothing is deleted and changed UNTIL you click "APPLY" and then confirm by clicking "OK". Confirm that you are selecting and flagging to delete the correct drive. Your SD card should be the smallest one present on your computer. Select it, with a right mouse click, select "Delete": Create FAT or FAT32 partition: Right mouse click over the SD card unallocated space, and click "create": From "Create As", select: PRIMARY From "File System", select: For SD card bellow 2GB: FAT For SD card above 2GB: FAT32 Under "Size and Location", at the right side, mouse left click and hold, then slide to the left to adjust the space for this partition. create ext2 or ext3 or swap partition: Right mouse click over the SD card unallocated space, and click "create": From "Create As", select: PRIMARY From "File System", select: For App2SD: ext2 For swap: Linux Swap Apply changes Now that all has been created, you just need to apply and confirm the changes: On the top left, there's a button labeled "Apply", press it: A confirmation popup should be presented, press "Yes": All done, your SD card can now return to your phone. If your current ROM is capable of using swap, it will detect and use it. Notes Please read everything carefully before proceeding. As mentioned by t0mm13b in the comments to your question, this subject as been covered, and the CyanogenMod team informs that this features are disabled by default due to potential issues: Swap and Compressed Cache (Compcache) are optional memory management systems. By default, these schemes are disabled due to potential issues with some configurations. Credits to: CyanogenMod Wiki - Swap and Compcache XDA Developers Forum - SD card partitioning