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Subject[PATCH 1/5] Documentation: nfs: convert pnfs.txt to ReST
From: "Daniel W. S. Almeida" <>

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

Signed-off-by: Daniel W. S. Almeida <>
Documentation/filesystems/index.rst | 1 +
Documentation/filesystems/nfs/index.rst | 9 +++++++
.../filesystems/nfs/{pnfs.txt => pnfs.rst} | 25 +++++++++++--------
3 files changed, 25 insertions(+), 10 deletions(-)
create mode 100644 Documentation/filesystems/nfs/index.rst
rename Documentation/filesystems/nfs/{pnfs.txt => pnfs.rst} (87%)

diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
index ad6315a48d14..801d773a44b9 100644
--- a/Documentation/filesystems/index.rst
+++ b/Documentation/filesystems/index.rst
@@ -48,3 +48,4 @@ Documentation for filesystem implementations.

+ nfs/index
diff --git a/Documentation/filesystems/nfs/index.rst b/Documentation/filesystems/nfs/index.rst
new file mode 100644
index 000000000000..d19ba592779a
--- /dev/null
+++ b/Documentation/filesystems/nfs/index.rst
@@ -0,0 +1,9 @@
+.. toctree::
+ :maxdepth: 1
+ pnfs
diff --git a/Documentation/filesystems/nfs/pnfs.txt b/Documentation/filesystems/nfs/pnfs.rst
similarity index 87%
rename from Documentation/filesystems/nfs/pnfs.txt
rename to Documentation/filesystems/nfs/pnfs.rst
index 80dc0bdc302a..7c470ecdc3a9 100644
--- a/Documentation/filesystems/nfs/pnfs.txt
+++ b/Documentation/filesystems/nfs/pnfs.rst
@@ -1,15 +1,17 @@
-Reference counting in pnfs:
+Reference counting in pnfs

The are several inter-related caches. We have layouts which can
reference multiple devices, each of which can reference multiple data servers.
Each data server can be referenced by multiple devices. Each device
-can be referenced by multiple layouts. To keep all of this straight,
+can be referenced by multiple layouts. To keep all of this straight,
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.

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:
+hashing and variations of this algorithm can be found `here.

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 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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