doc: Added a doc for filestore settings.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>

diff --git a/doc/config-cluster/filestore-config-ref.rst b/doc/config-cluster/filestore-config-ref.rst
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+============================
+ Filestore Config Reference
+============================
+
+
+Extended Attributes
+===================
+
+
+``filestore debug omap check``
+
+:Description: Debugging check on synchronization. Expensive. For debugging only.
+:Type: Boolean
+:Required: No
+:Default: ``0``
+
+
+``filestore xattr use omap``
+
+:Description: Use object map for XATTRS. Set to ``true`` for ``ext4`` file systems. 
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+``filestore max inline xattr size``
+
+:Description: The maximum size of an inlined XATTR in bytes. 
+:Type: Unsigned 32-bit Integer
+:Required: No
+:Default: 512
+
+
+``filestore max inline xattrs``
+
+:Description: 
+:Type: 32-bit Integer
+:Required: No
+:Default: ``2``
+
+
+Synchronization Intervals
+=========================
+
+Periodically, the filestore needs to quiesce writes and synchronize the filesystem,
+which creates a consistent commit point. It can then free journal entries up to
+the commit point. Synchronizing more frequently tends to reduce the time required 
+perform synchronization, and reduces the amount of data that needs to remain in the 
+journal. Less frequent synchronization allows the backing filesystem to coalesce 
+small writes and metadata updates more optimally--potentially resulting in more
+efficient synchronization.
+
+
+``filestore max sync interval``
+
+:Description: The maximum interval in seconds for synchronizing the filestore.
+:Type: Double
+:Required: No
+:Default: ``5``
+
+
+``filestore min sync interval``
+
+:Description: The minimum interval in seconds for synchronizing the filestore.
+:Type: Double
+:Required: No
+:Default: ``.01``
+
+
+Flusher
+=======
+
+The filestore flusher forces data from large writes to be written out
+using ``sync file range``
+before the sync in order to (hopefully) reduce the cost of the
+eventual sync. In practice,
+disabling 'filestore flusher' seems to improve performance in some cases.
+
+
+``filestore flusher``
+
+:Description: Enables the filestore flusher.
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+``filestore flusher max fds``
+
+:Description: Sets the maximum number of file descriptors for the flusher.
+:Type: Integer
+:Required: No
+:Default: ``512``
+
+``filestore sync flush``
+
+:Description: Enables the synchronization flusher. 
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+``filestore fsync flushes journal data``
+
+:Description: Flush journal data during filesystem synchronization.
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+Queue
+=====
+
+
+``filestore queue max ops``
+
+:Description: Defines the maximum number of in progress operations the file store accepts before blocking on queing new operations. 
+:Type: Integer
+:Required: No. Minimal impact on performance.
+:Default: ``500``
+
+
+``filestore queue max bytes``
+
+:Description: The maximum number of bytes for an operation. 
+:Type: Integer
+:Required: No
+:Default: ``100 << 20``
+
+
+``filestore queue committing max ops``
+
+:Description: The maximum number of operations the filestore can commit. 
+:Type: Integer
+:Required: No
+:Default: ``500``
+
+
+``filestore queue committing max bytes``
+
+:Description: The maximum number of bytes the filestore can commit.
+:Type: Integer
+:Required: No
+:Default: ``100 << 20``
+
+
+
+Timeouts
+========
+
+
+``filestore op threads``
+
+:Description: The number of filesystem operation threads that execute in parallel. 
+:Type: Integer
+:Required: No
+:Default: ``2``
+
+
+``filestore op thread timeout``
+
+:Description: The timeout for a filesystem operation thread (in seconds).
+:Type: Integer
+:Required: No
+:Default: ``60``
+
+
+``filestore op thread suicide timeout``
+
+:Description: The timeout for a commit operation before cancelling the commit (in seconds). 
+:Type: Integer
+:Required: No
+:Default: ``180``
+
+
+B-Tree Filesystem
+=================
+
+
+``filestore btrfs snap``
+
+:Description: Enable snapshots for a ``btrfs`` filestore.
+:Type: Boolean
+:Required: No. Only used for ``btrfs``.
+:Default: ``true``
+
+
+``filestore btrfs clone range``
+
+:Description: Enable cloning ranges for a ``btrfs`` filestore.
+:Type: Boolean
+:Required: No. Only used for ``btrfs``.
+:Default: ``true``
+
+
+Extent Mapping
+==============
+
+
+``filestore fiemap``
+
+:Description: Allows an OSD to determine which bits of a file have been written. For efficient sparse reads. 
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+OPTION(filestore_fiemap_threshold, OPT_INT, 4096)
+
+
+
+
+
+//Todo:
+
+
+``filestore``
+
+:Description: IGNORE FOR NOW
+:Type: Boolean
+:Required: No
+:Default: ``false``
+
+
+OPTION(filestore_journal_parallel, OPT_BOOL, false)
+OPTION(filestore_journal_writeahead, OPT_BOOL, false)
+OPTION(filestore_journal_trailing, OPT_BOOL, false)
+OPTION(filestore_merge_threshold, OPT_INT, 10)
+OPTION(filestore_split_multiple, OPT_INT, 2)
+OPTION(filestore_update_to, OPT_INT, 1000)
+OPTION(filestore_blackhole, OPT_BOOL, false)     // drop any new transactions on the floor
+OPTION(filestore_dump_file, OPT_STR, "")         // file onto which store transaction dumps
+OPTION(filestore_kill_at, OPT_INT, 0)            // inject a failure at the n'th opportunity
+OPTION(filestore_fail_eio, OPT_BOOL, true)       // fail/crash on EIO