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Documentation: nfs: convert pnfs.txt to ReST

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Convert pnfs.txt to ReST. Content remains mostly unchanged.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/20200129044917.566906-2-dwlsalmeida@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Daniel W. S. Almeida 2020-01-29 01:49:13 -03:00 committed by Jonathan Corbet
parent bb6d3fb354
commit 34e75cf4be
3 changed files with 25 additions and 10 deletions
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1
Documentation/filesystems/index.rst
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@ -51,3 +51,4 @@ Documentation for filesystem implementations.
overlayfs
virtiofs
vfat
nfs/index

9
Documentation/filesystems/nfs/index.rst Normal file
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@ -0,0 +1,9 @@
===============================
NFS
===============================
.. toctree::
:maxdepth: 1
pnfs

23
Documentation/filesystems/nfs/pnfs.txt → Documentation/filesystems/nfs/pnfs.rst
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@ -1,4 +1,5 @@
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