Making this interface thread-safe...

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 59b5931)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit c0d0fa8)

This ptr is like a unique_ptr except it allocates the underlying object on
access. The idea being that we can save memory if the object is only needed
sometimes.

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 5fa557d)

The gymnastics protecting the map failed as the code evolved. Just expose it
normally with a getter.

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit d1b6cad)

The purpose of this is to allow us to track memory usage by cached objects so
we can limit cache size based on memory available/allocated to the MDS.

This commit is a first step: it adds CInode, CDir, and CDentry to the mempool
but not all of the containers in these classes (e.g. std::map). However,
MDSCacheObject has been changed to allocate its containers through the mempool
by converting compact_* containers to the std versions offered through mempool
via the new alloc_ptr.

(A compact_* class simply wraps a pointer to the std:: version to reduce memory
usage of an object when the container is only occasionally used. The alloc_ptr
allows us to achieve the same thing explicitly with only a little handholding:
when all entries in the wrapped container are deleted, the caller must call
alloc_ptr.release().)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit e035b64)

Zheng observed that an alloc_ptr doesn't really work in this case since any
call to get_replicas() will cause the map to be allocated, nullifying the
benefit. Use a compact_map until a better solution can be written. (This means
that the map will be allocated outside the mempool.)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 5d67b5c)

This prevents accidental allocation of the map.

Also, privatize the variable to protect from this in child classes.

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 055020c)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 7fff24e)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 0ddd260)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 0c2032c)

Avoids an unnecessary "max" size of the LRU which was used to calculate the
midpoint. Instead, just dynamically move the LRUObjects between top and bottom
on-the-fly.

This change is necessary for a cache which which does not limit by the number
of objects but by some other metric. (In this case, memory.)

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 12d615b)

This introduces two config parameters:

    mds_cache_memory_limit: Sets the soft maximum of the cache to the given
    byte count. (Like mds_cache_size, this doesn't actually limit the maximum
    size of the cache. It just dictates the steady-state size.)

    mds_cache_reservation: This replaces mds_health_cache_threshold everywhere
    except the Beacon heartbeat sent to the mons. The idea here is to specify a
    reservation of memory (5% by default) for operations and the MDS tries to
    always maintain that reservation. So, the MDS will recall caps from clients
    when it begins dipping into its reservation of memory.

mds_cache_size still limits the cache by Inode count but is now by-default 0
(i.e. unlimited). The new preferred way of specifying cache limits is by memory
size. The default is 1GB.

Fixes: http://tracker.ceph.com/issues/20594
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1464976

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 06c94de)

 Conflicts:
	PendingReleaseNotes
	src/mds/MDCache.cc

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
(cherry picked from commit fd44740)

avoid iterating dentries if dirfrag is non-auth

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
(cherry picked from commit d32a237)