Documentation: nfs: convert pnfs.txt to ReST (34e75cf4) · Commits · 戴 / test

Documentation/filesystems/index.rst

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		@@ -51,3 +51,4 @@ Documentation for filesystem implementations.
		overlayfs
		virtiofs
		vfat
		nfs/index

Documentation/filesystems/nfs/index.rst

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		===============================
		NFS
		===============================


		.. toctree::
		:maxdepth: 1

		pnfs

Documentation/filesystems/nfs/pnfs.txt→Documentation/filesystems/nfs/pnfs.rst

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		Reference counting in pnfs:
		==========================
		Reference counting in pnfs
		==========================

		The are several inter-related caches. We have layouts which can
		@@ -9,7 +10,8 @@ we need to reference count.


		struct pnfs_layout_hdr
		----------------------
		======================

		The on-the-wire command LAYOUTGET corresponds to struct
		pnfs_layout_segment, usually referred to by the variable name lseg.
		Each nfs_inode may hold a pointer to a cache of these layout
		@@ -25,7 +27,8 @@ the reference count, as the layout is kept around by the lseg that
		keeps it in the list.

		deviceid_cache
		--------------
		==============

		lsegs reference device ids, which are resolved per nfs_client and
		layout driver type. The device ids are held in a RCU cache (struct
		nfs4_deviceid_cache). The cache itself is referenced across each
		@@ -38,24 +41,26 @@ justification, but seems reasonable given that we can have multiple
		deviceid's per filesystem, and multiple filesystems per nfs_client.

		The hash code is copied from the nfsd code base. A discussion of
		hashing and variations of this algorithm can be found at:
		http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809
		hashing and variations of this algorithm can be found `here.
		<http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809>`_

		data server cache
		-----------------
		=================

		file driver devices refer to data servers, which are kept in a module
		level cache. Its reference is held over the lifetime of the deviceid
		pointing to it.

		lseg
		----
		====

		lseg maintains an extra reference corresponding to the NFS_LSEG_VALID
		bit which holds it in the pnfs_layout_hdr's list. When the final lseg
		is removed from the pnfs_layout_hdr's list, the NFS_LAYOUT_DESTROYED
		bit is set, preventing any new lsegs from being added.

		layout drivers
		--------------
		==============

		PNFS utilizes what is called layout drivers. The STD defines 4 basic
		layout types: "files", "objects", "blocks", and "flexfiles". For each
		@@ -68,6 +73,6 @@ Blocks-layout-driver code is in: fs/nfs/blocklayout/.. directory
		Flexfiles-layout-driver code is in: fs/nfs/flexfilelayout/.. directory

		blocks-layout setup
		-------------------
		===================

		TODO: Document the setup needs of the blocks layout driver

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