various bugfix without pr

[Alkaid-Benetnash]

should use function parameter instead of file descriptor's offset field
please see this commit

[Alkaid-Benetnash]

and more bugs, just paste patches here since maybe no one really look at this issue.
log invalidation bug related to log_version
incomplete log block bug
log invalidation bug related to digesting and RO/RW log
libfs outdated extents block buffer bug (ugly workaround, correctness first as time limiting)
kernfs dirty buffer writeback and refcount bug
directory block out of range access
potential deadloop with compiler optimization, since shared variable accessed without protection

[iangneal]

ftruncate bug due to bad end block calculation.
Can be tested in libfs/tests/ftrunc_test. Notably, the old way had a bug if the file size was less than 4k and a truncate to 0 was specified. This fixes that

[iangneal]

unlink bug fix

[Alkaid-Benetnash]

root inode->i_sb not initialized
inode->fcache_hash used after free
x86_64 calling convention of syscall are different from function call
(workaround) sigaction put struct on callee's stack

[Alkaid-Benetnash]

Should persist log data before updating fcache_block metadata
Should atomically update log version related variable
The time really read from app log isn't the same as checking if log is valid, maintain a safe distance to prevent concurrency bugs
Didn't add each kernfs dirty buffer to writeback list, previous fix "kernfs dirty buffer writeback and refcount bug" was incomplete