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ceph: enable/disable dentry complete flags via mount option

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Enable/disable use of the dentry dir 'complete' flag via a mount option.
This lets the admin control whether ceph uses the dcache to satisfy
negative lookups or readdir when it has the entire directory contents in
its cache.

This is purely a performance optimization; correctness is guaranteed
whether it is enabled or not.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil
2012-01-10 09:12:55 -08:00
parent 46f72b3492
commit a40dc6cc2e
4 changed files with 50 additions and 8 deletions
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18
Documentation/filesystems/ceph.txt
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@@ -119,12 +119,20 @@ Mount Options
must rely on TCP's error correction to detect data corruption
in the data payload.
noasyncreaddir
Disable client's use its local cache to satisfy readdir
requests. (This does not change correctness; the client uses
cached metadata only when a lease or capability ensures it is
valid.)
dcache
Use the dcache contents to perform negative lookups and
readdir when the client has the entire directory contents in
its cache. (This does not change correctness; the client uses
cached metadata only when a lease or capability ensures it is
valid.)
nodcache
Do not use the dcache as above. This avoids a significant amount of
complex code, sacrificing performance without affecting correctness,
and is useful for tracking down bugs.
noasyncreaddir
Do not use the dcache as above for readdir.
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