DAOS-14411 dfuse: Add daos fs query

Multiple cherry-picks to add daos fs query feature for fuse
statistics.  Helpful for understanding and tuning DAOS
performance when dfuse is used.

DAOS-13625 dfuse: Merge the info and projection_info structs. (#11881)
DAOS-13658 dfuse: Add filesystem query command. (#12367)
DAOS-12751 control: Add a daos filesystem evict command. (#12331)
DAOS-12751 dfuse: Improve evict command. (#12633)
DAOS-13625 dfuse: Remove dfuse_projection_info entirely. (#12796)
DAOS-13625 dfuse: Replace fs_handle with dfuse_info. (#12894)
DAOS-13625 dfuse: Add core inode_lookup() and inode_decref() functions. (#12573)
DAOS-14411 dfuse: Add per-container statistics. (#12819)
DAOS-14411 control: Expose dfuse statistics as yaml. (#13876)

Features: dfuse

Required-githooks: true

Change-Id: I8ae3cc743697c2434ae0d54b382ee6c585a3b033
Signed-off-by: Ashley Pittman <ashley.m.pittman@intel.com>
Signed-off-by: Jeff Olivier <jeffolivier@google.com>

docs/user/filesystem.md

@@ -696,6 +696,30 @@ These are two command line options to control the DFuse process itself.
 
 These will affect all containers accessed via DFuse, regardless of any container attributes.
 
+### Managing memory usage and disconnecting from containers
+
+DFuse can be instructed to evict paths from local memory which drops any open handles on containers
+or pools as well as reducing the working set size and memory consumption. This is an asynchronous
+operation and there is no automatic way to tell if it's completed. In addition, any lookup of the
+path specified in the eviction call will cause a new lookup and prevent the eviction from
+completing.
+
+Paths can be requested for eviction from dfuse using the `daos filesystem evict` command. This does
+not change any data that is stored in DAOS in any way but rather releases local resources. This
+command will return the inode number of the path as well as key dfuse metrics.
+
+DFuse metrics can be queried with the `daos filesystem query` command which takes an optional
+`--inode` parameter. This will return information on the number of inodes held in memory, the
+number of open files as well as the number of pools and containers that DFuse is connected to. If
+the `--inode` option is given then this command will also report if the inode is in memory or not.
+
+Together these two commands can be used to request eviction of a path and to poll for its release,
+although lookups from other processes might block the eviction process.
+
+If `daos filesystem evict` is passed the root of the DFuse mount then the path itself cannot be
+evicted - in this case all top-level entries in the directory are evicted instead and no inode
+number is returned.
+
 ### Permissions
 
 DFuse can serve data from any user's container, but needs appropriate permissions in order to do