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-rw-r--r--Documentation/device-mapper/cache.txt11
1 files changed, 5 insertions, 6 deletions
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index e6b72d355151..68c0f517c60e 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -124,12 +124,11 @@ the default being 204800 sectors (or 100MB).
124Updating on-disk metadata 124Updating on-disk metadata
125------------------------- 125-------------------------
126 126
127On-disk metadata is committed every time a REQ_SYNC or REQ_FUA bio is 127On-disk metadata is committed every time a FLUSH or FUA bio is written.
128written. If no such requests are made then commits will occur every 128If no such requests are made then commits will occur every second. This
129second. This means the cache behaves like a physical disk that has a 129means the cache behaves like a physical disk that has a volatile write
130write cache (the same is true of the thin-provisioning target). If 130cache. If power is lost you may lose some recent writes. The metadata
131power is lost you may lose some recent writes. The metadata should 131should always be consistent in spite of any crash.
132always be consistent in spite of any crash.
133 132
134The 'dirty' state for a cache block changes far too frequently for us 133The 'dirty' state for a cache block changes far too frequently for us
135to keep updating it on the fly. So we treat it as a hint. In normal 134to keep updating it on the fly. So we treat it as a hint. In normal