journal

Ext3 Journal Implementation

Blog post by jvff on Thu, 2010-08-05 00:49
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The fundamental parts of the journal code are finished. Although they still need more testing, and they can change as more of the Ext3 code is written, they are ready for supporting the first steps in write support for ext2 and ext3 volumes. This blog post explains the code, and how it is organized to handle ext2 and ext3 volumes.

Another BFS surprise

Blog post by axeld on Tue, 2005-10-18 23:25
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Turns out BFS logging code is not that intelligent - it uses block_runs in the log area, but it doesn't make use of them. In other words: it only accepts block_runs with length 1 - which effectively kills the whole idea of using them. It's now as space consuming as the single block number arrays I had before, but doesn't share the binary search capability we had earlier.

While our code now could use block_runs how they should be used, I have disabled joining separate block_runs to make our BFS fully compatible to Be's in this regard. If we someday leave compatibility with the current BFS behind, we can enable it again, of course.

Analyze This

Blog post by axeld on Tue, 2005-10-18 10:00
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This morning, I went through analyzing the BFS log area structure. Turns out it's very different from what I did for our BFS.
Our current log structure looks like this:


block 1 - n:
 uint64      number of blocks
 off_t[]     array of block numbers
block n+1 - m:
 real block data

While the one from BFS looks like this:


block 1:
 uint32      number of runs
 uint32      max. number of runs
 block_run[] array of block runs
block 2 - m:
 real block data
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