4 ms·

At this point you must know that if you buy a mac you are surrendering any claim on your third party apps surviving between updates. Irritating, yes, but not su

At this point you must know that if you buy a mac you are surrendering any claim on your third party apps surviving between updates. Irritating, yes, but not surprising.

catiopatio 4y ago
Apple isn't remotely to blame for this; the RPi bootloader exposes a broken, incorrect emulation of the USB mass storage protocol. The only way this ever worked was pure luck, relying on the OS: - Writing file blocks in the desired order — which is not guaranteed. - Writing filesystem metadata in the desired order — also not guaranteed. - Not caching any important pages, so that the VM page cache isn't out-of-sync with the block device after it silently discards writes. - Not caching any important filesystem metadata, so that the filesystem implementation isn't out-of-sync. I'm surprised (1) anyone thought this was anything other than a risky hack, and (2) not only did RPi actually ship this broken design, but did so in ROM, and thus cannot patch it. [edit] Surprised at the downvotes for posting a technical rebuttal to an inflammatory comment. As someone with a few decades in OS/kernel development, this doesn't seem like a controversial or even difficult question. The implementation is broken and cannot work reliably. If you disagree, then please explain why you believe the USB mass storage emulation is not broken.
- devanl 4y ago
  In case you haven't seen the UF2 file format, it's specifically designed to be robust w.r.t ensuring that the content makes it to the target intact despite common OS quirks. https://github.com/microsoft/uf2 https://github.com/microsoft/uf2 - Data is divided into 512 byte blocks, which lines up with the mass storage transfer size. - Each block has an identifying magic sequence, a payload address, and size, which can be used to identify the destination. - This allows the emulated storage to ignore metadata blocks and to handle out-of-order and repeated blocks.
  - catiopatio 4y ago
    The UF2 format is a hack that can be made to generally work (e.g. it relies on things like per-block beginning and ending magic numbers to identify blocks that should be written to flash, which means isn't dependent on seeing FAT table writes in a particular order). UF2 is just the file format, though. The mechanism for reading/writing UF2 files is via the emulated USB mass storage, which is fundamentally broken. The USB storage device responds to SCSI write commands with a success status, but actually throws away data, such that a successive read does not return the previously written blocks. To an OS or filesystem, that's just a failing drive. You might get lucky and things might work.
- uranusjr 4y ago
  I don’t understand any of the technical details involved here, but reading your comments makes me seriously wondering, does RPi rely on these everywhere, or just when plugged to a Mac? Because all three things seem like pretty reasonable optimisation opportunities for a file manager to implement, and given how USB storage devices have been around I’m very surprised if they managed to get away without issues until now.

At this point you must know that if you buy a mac you are surrendering any claim on your third party apps surviving between updates. Irritating, yes, but not surprising.

catiopatio 4y ago

Apple isn't remotely to blame for this; the RPi bootloader exposes a broken, incorrect emulation of the USB mass storage protocol. The only way this ever worked was pure luck, relying on the OS: - Writing file blocks in the desired order — which is not guaranteed. - Writing filesystem metadata in the desired order — also not guaranteed. - Not caching any important pages, so that the VM page cache isn't out-of-sync with the block device after it silently discards writes. - Not caching any important filesystem metadata, so that the filesystem implementation isn't out-of-sync. I'm surprised (1) anyone thought this was anything other than a risky hack, and (2) not only did RPi actually ship this broken design, but did so in ROM, and thus cannot patch it. [edit] Surprised at the downvotes for posting a technical rebuttal to an inflammatory comment. As someone with a few decades in OS/kernel development, this doesn't seem like a controversial or even difficult question. The implementation is broken and cannot work reliably. If you disagree, then please explain why you believe the USB mass storage emulation is not broken.

devanl 4y ago
In case you haven't seen the UF2 file format, it's specifically designed to be robust w.r.t ensuring that the content makes it to the target intact despite common OS quirks. https://github.com/microsoft/uf2 https://github.com/microsoft/uf2 - Data is divided into 512 byte blocks, which lines up with the mass storage transfer size. - Each block has an identifying magic sequence, a payload address, and size, which can be used to identify the destination. - This allows the emulated storage to ignore metadata blocks and to handle out-of-order and repeated blocks.
- catiopatio 4y ago
  The UF2 format is a hack that can be made to generally work (e.g. it relies on things like per-block beginning and ending magic numbers to identify blocks that should be written to flash, which means isn't dependent on seeing FAT table writes in a particular order). UF2 is just the file format, though. The mechanism for reading/writing UF2 files is via the emulated USB mass storage, which is fundamentally broken. The USB storage device responds to SCSI write commands with a success status, but actually throws away data, such that a successive read does not return the previously written blocks. To an OS or filesystem, that's just a failing drive. You might get lucky and things might work.
uranusjr 4y ago
I don’t understand any of the technical details involved here, but reading your comments makes me seriously wondering, does RPi rely on these everywhere, or just when plugged to a Mac? Because all three things seem like pretty reasonable optimisation opportunities for a file manager to implement, and given how USB storage devices have been around I’m very surprised if they managed to get away without issues until now.