Implement homeblock write path.

[sanebay]

Write flow writes data to disk, add key value to index and flush journal entry to journal. Add test case to test the normal io flow.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 86.43068% with 46 lines in your changes missing coverage. Please review.

Project coverage is 80.11%. Comparing base (0b40663) to head (ca1d0fa).
Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lib/volume_mgr.cpp	82.95%	9 Missing and 6 partials ⚠️
src/lib/volume/index.hpp	73.58%	10 Missing and 4 partials ⚠️
src/lib/listener.cpp	55.55%	4 Missing ⚠️
src/lib/volume/tests/test_volume_io.cpp	96.55%	0 Missing and 4 partials ⚠️
src/lib/index.cpp	82.35%	2 Missing and 1 partial ⚠️
src/lib/volume/tests/test_common.hpp	92.50%	1 Missing and 2 partials ⚠️
src/lib/homeblks_impl.hpp	85.71%	0 Missing and 2 partials ⚠️
src/include/homeblks/volume_mgr.hpp	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##             main      #86       +/-   ##
===========================================
+ Coverage   61.68%   80.11%   +18.43%     
===========================================
  Files          15       17        +2     
  Lines         462      835      +373     
  Branches       35       80       +45     
===========================================
+ Hits          285      669      +384     
+ Misses        158      125       -33     
- Partials       19       41       +22     

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[yamingk]

I fail to follow the need of the MessageHeader here.
It seems from the code walk through, the only field we need is the msg_type, I am also not quite sure we even need this, as READ seems doesn't require on_commit in its path, right? It returns a future and future thenValue can get the data when it is done, right? Do we need to do anything for read in on_commit path as well?

For unmap, it is async op, to free the blocks, caller doesn't need to wait for free blks to actually freed, it can be similar as read, that after index removed the lbas, unmap's future's thenValue can return the call, right?

[sanebay]

Yeah for read we dont need on_commit, but unmap needs it because if we crash, we will have leaks. Unmap will write the blkid's to free and call on_commit where it do async_free_blks. But if it crashe, recovery will find unmap type and call async_free_blks again. Right MessageHeader we can avoid since we already have CRC for write payload, its only help to find any corruption in journal entries.

[yamingk]

For unmap, we should call index->unmap directly and index will call free_blks (same as destory index). It shouldn't need to call on_commit. Unmap can write journal entry for crash recovery, on journal reply it should just call index->unmap.

[sanebay]

As discussed, unmap will do range remove of keys from index, gets the existing blkid's with filter cb, and write to journal. In on_commit we can async free the blks.

[raakella1]

The changes look good to me.