Increase maximum block size allowed by IMFS

[Joel Sherrill]

In imfs_initsupp.c, there is code to limit the maximum block size for the IMFS to a power of two <= 512. This code was written a long time ago (at least 15 years) and at that point having a lot of RAM was inconceivable. I am proposing to increase the limit to at least 8192.

I am not proposing we change the default which is currently 128 bytes. This gives a maximum file size of ~1GB.

Increasing it to 8192 would make the limit approximately 16GB.

[Sebastian Huber]

Are you sure that there are no 32-bit integer overflows in this case? How can you test this? Is there a demand for such a large IMFS file?

[Joel Sherrill]

I was just asking if the limit needs to be increased since it was set 15 years ago. There are no users needing this. When designed 16MB was more RAM than I had seen on an RTEMS system. Now we see much more than that on USD35 boards.

You are right that we don't want to overflow a 32-bit integer. That may mean the practical limit is 1024 (2GB filesystem) or 2048.

But do we want to do this at all?

[Chris Johns]

For large RAM based file systems I use a RAM disk formatted with the RFS. For example I currently has a 32M RAM disk on a board with the RFS and this avoids fragmenting of the heap.

I do not see a need for this change.

[Chris Johns]

Please reopen if this issue is still valid.