docs: filesystems: convert caching/object.txt to ReST
- Add a SPDX header; - Adjust document and section titles; - Comment out text ToC for html/pdf output; - Some whitespace fixes and new line breaks; - Adjust the events list to make them look better for html output; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/49026a8ea7e714c2e0f003aa26b975b1025476b7.1588021877.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Mauro Carvalho Chehab
Jonathan Corbet
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@ -191,7 +191,7 @@ The cache backend API to FS-Cache can be found in:
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A description of the internal representations and object state machine can be
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found in:
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Documentation/filesystems/caching/object.txt
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Documentation/filesystems/caching/object.rst
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=======================
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@ -0,0 +1,9 @@
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.. SPDX-License-Identifier: GPL-2.0
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Filesystem Caching
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==================
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.. toctree::
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:maxdepth: 2
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object
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@ -1,10 +1,12 @@
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====================================================
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IN-KERNEL CACHE OBJECT REPRESENTATION AND MANAGEMENT
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====================================================
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.. SPDX-License-Identifier: GPL-2.0
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====================================================
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In-Kernel Cache Object Representation and Management
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====================================================
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By: David Howells <dhowells@redhat.com>
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Contents:
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.. Contents:
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(*) Representation
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@ -18,8 +20,7 @@ Contents:
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(*) The set of events.
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==============
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REPRESENTATION
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Representation
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==============
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FS-Cache maintains an in-kernel representation of each object that a netfs is
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@ -38,7 +39,7 @@ or even by no objects (it may not be cached).
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Furthermore, both cookies and objects are hierarchical. The two hierarchies
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correspond, but the cookies tree is a superset of the union of the object trees
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of multiple caches:
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of multiple caches::
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NETFS INDEX TREE : CACHE 1 : CACHE 2
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: :
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@ -89,8 +90,7 @@ pointers to the cookies. The cookies themselves and any objects attached to
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those cookies are hidden from it.
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===============================
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OBJECT MANAGEMENT STATE MACHINE
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Object Management State Machine
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===============================
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Within FS-Cache, each active object is managed by its own individual state
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@ -124,7 +124,7 @@ is not masked, the object will be queued for processing (by calling
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fscache_enqueue_object()).
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PROVISION OF CPU TIME
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Provision of CPU Time
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---------------------
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The work to be done by the various states was given CPU time by the threads of
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@ -141,7 +141,7 @@ because:
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workqueues don't necessarily have the right numbers of threads.
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LOCKING SIMPLIFICATION
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Locking Simplification
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----------------------
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Because only one worker thread may be operating on any particular object's
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@ -151,8 +151,7 @@ from the cache backend's representation (fscache_object) - which may be
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requested from either end.
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=================
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THE SET OF STATES
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The Set of States
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=================
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The object state machine has a set of states that it can be in. There are
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@ -275,19 +274,17 @@ memory and potentially deletes stuff from disk:
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this state.
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THE SET OF EVENTS
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The Set of Events
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-----------------
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There are a number of events that can be raised to an object state machine:
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(*) FSCACHE_OBJECT_EV_UPDATE
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FSCACHE_OBJECT_EV_UPDATE
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The netfs requested that an object be updated. The state machine will ask
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the cache backend to update the object, and the cache backend will ask the
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netfs for details of the change through its cookie definition ops.
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(*) FSCACHE_OBJECT_EV_CLEARED
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FSCACHE_OBJECT_EV_CLEARED
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This is signalled in two circumstances:
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(a) when an object's last child object is dropped and
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@ -296,20 +293,16 @@ There are a number of events that can be raised to an object state machine:
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This is used to proceed from the dying state.
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(*) FSCACHE_OBJECT_EV_ERROR
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FSCACHE_OBJECT_EV_ERROR
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This is signalled when an I/O error occurs during the processing of some
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object.
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(*) FSCACHE_OBJECT_EV_RELEASE
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(*) FSCACHE_OBJECT_EV_RETIRE
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FSCACHE_OBJECT_EV_RELEASE, FSCACHE_OBJECT_EV_RETIRE
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These are signalled when the netfs relinquishes a cookie it was using.
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The event selected depends on whether the netfs asks for the backing
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object to be retired (deleted) or retained.
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(*) FSCACHE_OBJECT_EV_WITHDRAW
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FSCACHE_OBJECT_EV_WITHDRAW
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This is signalled when the cache backend wants to withdraw an object.
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This means that the object will have to be detached from the netfs's
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cookie.
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@ -25,6 +25,8 @@ algorithms work.
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locking
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directory-locking
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caching/index
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porting
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Filesystem support layers
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@ -4,7 +4,7 @@
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* See Documentation/filesystems/caching/object.txt for a description of the
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* See Documentation/filesystems/caching/object.rst for a description of the
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* object state machine and the in-kernel representations.
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*/
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