Add LFS_F_WRUNCHECKED option to avoid validation and hence reading blocks when writing

[andyp1per]

In ArduPilot we predominantly stream logs to disk while flying. In our current block logger we do this without validation and this PR adds an option to skip validation while writing to streamline the writing process.

Also fixes a build issue with the file backend when compiling without debug.

[geky-bot]

Tests passed ✓, Code: 17136 B (+0.0%), Stack: 1440 B (+0.0%), Structs: 812 B (+0.0%)

	Code	Stack	Structs		Coverage
Default	17136 B (+0.0%)	1440 B (+0.0%)	812 B (+0.0%)	Lines	2400/2572 lines (-0.0%)
Readonly	6250 B (+0.0%)	448 B (+0.0%)	812 B (+0.0%)	Branches	1283/1616 branches (+0.0%)
Threadsafe	17984 B (+0.0%)	1440 B (+0.0%)	820 B (+0.0%)		Benchmarks
Multiversion	17208 B (+0.0%)	1440 B (+0.0%)	816 B (+0.0%)	Readed	29369693876 B (+0.0%)
Migrate	18824 B (+0.0%)	1736 B (+0.0%)	816 B (+0.0%)	Proged	1482874766 B (+0.0%)
Error-asserts	17900 B (+0.0%)	1432 B (+0.0%)	812 B (+0.0%)	Erased	1568888832 B (+0.0%)

[geky]

Hi @andyp1per, thanks for creating a PR.

Have you considered making this a filesystem-wide ifdef, say, LFS_NO_CKPROGS? That way you could also avoid the reads to validate metadata commits (here). I have a similar thing on a fork (albeit via mount flags).

I'm curious, did this impact performance noticeably? I've been viewing this as low priority as I assumed the read overhead for validation would always be overshadowed by the related prog+erase overhead.

[andyp1per]

Hi @andyp1per, thanks for creating a PR.

Have you considered making this a filesystem-wide ifdef, say, LFS_NO_CKPROGS? That way you could also avoid the reads to validate metadata commits (here). I have a similar thing on a fork (albeit via mount flags).

I'm curious, did this impact performance noticeably? I've been viewing this as low priority as I assumed the read overhead for validation would always be overshadowed by the related prog+erase overhead.

I am interested in other types of file being checked, that's why I went for a per-file option. It might also be possible to set it temporarily - so for instance our logs are self-describing, we probably want the description to be stored reliably but the data not so much.

read is about 10x faster than write and it also chews up the SPI bus, so not nothing - in my testing so far this plus avoiding checking the file size seems to get me where I need to, but I need to do another full flight test to fully check