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70c5bab971
Implemented cache options in F2FS configuration 'c' (i.e. user
options):
* use c.cache_config.num_cache_entry to set the number of
cache entries (in block), minimum 1024, or 0 to disable cache.
* use c.cache_config.max_hash_collision to set maximum hash
collision (max 16).
* use c.cavhe_config.dbg_en to enable printing of debug messages.
Cache properties:
* Per block save based (block size = f2fs block size = 4K Bytes)
* Device block indices are used to hash (simple modular hash
function) to cache indices.
* A hash collision (when a block is hashed to an already occupied
cache block) will trigger offset-based relocation to max 16
other places, at first empty slot found policy.
* A hash collision with all 17 possible relocating places occupied
will evict the oldest used one (replaced by the new read block).
A global 'use' tick is kept ticking-up per block read for this
purpose.
* On write cache hit, it will update the corresponding cached
block.
* On write cache miss, the data won't be cached.
* Write-through policy only: never delayed write.
* On read cache hit, it returns the cached block.
* On read cache miss, it issues an I/O read to the kernel, and
then caches and returns the block.
* Currently read ahead is not implemented. Yet, the read ahead
logic is kept as before, i.e. using kernel's read ahead
mechanism.
Signed-off-by: Robin Hsu <robinhsu@google.com>
[Jaegeuk Kim: Fix one bug in dcache_update_rw()]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>