Can not write android external SD card while downloading books from the cloud storage

[kingo132]

• KOReader version: V2019.12
• Device: Hisense A5

Issue

Can not write android external SD card while downloading books from the cloud storage

Steps to reproduce

1. Try to download a book from cloud storage
2. Select any external sd card as the destination
3. It will fail with the message: Could not save to /storage/xxx/xxx.epub
4. If you choose the internal sd card as the destination, then all is ok without problem

[pazos]

Like #4872. Same unfixable underlying issue: there's no filesystem write permission outside the primary storage. It is mentioned at the bottom of https://www.mobileread.com/forums/showpost.php?p=3935915&postcount=1

Note that primary storage can be a sdcard if the user selected that as the main storage on android settings.

A workaround would be disable operations that require write permissions if the path is outside the sandbox. We already have android.isPathInsideSandbox(path) and a generic wrapper isValidPath(path) that can be used in these cases. It is actually used in android to disable import on dirs outside the sandbox

[clach04]

@kingo132 are you still seeing a message when this fails? Or does koreader exit without an error message?

[pazos]

@clach04: I'm afraid this is device/vendor dependant. The only reason for a crash here is an unhandled exception that crashes the entire java machine. Please get us a log to see what happens.

[clach04]

Thanks @pazos I got access to a machine where I could issue ADB :)

I attached an extract to #6636 (I can attach more if needed).

[pazos]

Thank you @clach04, the crash should be fixed with #6640. The underlying issue cannot be fixed. I'm closing this one.

Feel free to open other issues if you find other crashes related to RO filesystems (with logs, please :))