summaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2020-12-15 18:52:30 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-15 18:52:30 -0800
commit1a50ede2b3c846761a71c409f53e9121311a13c2 (patch)
tree40f228239b077c2db87580dfd66556ad0ca7046f /Documentation
parent9867cb1fd510187d8f828540bdb48f78fceb70b3 (diff)
parent716a8bc7f706eeef80ab42c99d9f210eda845c81 (diff)
Merge tag 'nfsd-5.11' of git://git.linux-nfs.org/projects/cel/cel-2.6
Pull nfsd updates from Chuck Lever: "Several substantial changes this time around: - Previously, exporting an NFS mount via NFSD was considered to be an unsupported feature. With v5.11, the community has attempted to make re-exporting a first-class feature of NFSD. This would enable the Linux in-kernel NFS server to be used as an intermediate cache for a remotely-located primary NFS server, for example, even with other NFS server implementations, like a NetApp filer, as the primary. - A short series of patches brings support for multiple RPC/RDMA data chunks per RPC transaction to the Linux NFS server's RPC/RDMA transport implementation. This is a part of the RPC/RDMA spec that the other premiere NFS/RDMA implementation (Solaris) has had for a very long time, and completes the implementation of RPC/RDMA version 1 in the Linux kernel's NFS server. - Long ago, NFSv4 support was introduced to NFSD using a series of C macros that hid dprintk's and goto's. Over time, the kernel's XDR implementation has been greatly improved, but these C macros have remained and become fallow. A series of patches in this pull request completely replaces those macros with the use of current kernel XDR infrastructure. Benefits include: - More robust input sanitization in NFSD's NFSv4 XDR decoders. - Make it easier to use common kernel library functions that use XDR stream APIs (for example, GSS-API). - Align the structure of the source code with the RFCs so it is easier to learn, verify, and maintain our XDR implementation. - Removal of more than a hundred hidden dprintk() call sites. - Removal of some explicit manipulation of pages to help make the eventual transition to xdr->bvec smoother. - On top of several related fixes in 5.10-rc, there are a few more fixes to get the Linux NFSD implementation of NFSv4.2 inter-server copy up to speed. And as usual, there is a pinch of seasoning in the form of a collection of unrelated minor bug fixes and clean-ups. Many thanks to all who contributed this time around!" * tag 'nfsd-5.11' of git://git.linux-nfs.org/projects/cel/cel-2.6: (131 commits) nfsd: Record NFSv4 pre/post-op attributes as non-atomic nfsd: Set PF_LOCAL_THROTTLE on local filesystems only nfsd: Fix up nfsd to ensure that timeout errors don't result in ESTALE exportfs: Add a function to return the raw output from fh_to_dentry() nfsd: close cached files prior to a REMOVE or RENAME that would replace target nfsd: allow filesystems to opt out of subtree checking nfsd: add a new EXPORT_OP_NOWCC flag to struct export_operations Revert "nfsd4: support change_attr_type attribute" nfsd4: don't query change attribute in v2/v3 case nfsd: minor nfsd4_change_attribute cleanup nfsd: simplify nfsd4_change_info nfsd: only call inode_query_iversion in the I_VERSION case nfs_common: need lock during iterate through the list NFSD: Fix 5 seconds delay when doing inter server copy NFSD: Fix sparse warning in nfs4proc.c SUNRPC: Remove XDRBUF_SPARSE_PAGES flag in gss_proxy upcall sunrpc: clean-up cache downcall nfsd: Fix message level for normal termination NFSD: Remove macros that are no longer used NFSD: Replace READ* macros in nfsd4_decode_compound() ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/nfs/exporting.rst52
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
index 33d588a01ace..0e98edd353b5 100644
--- a/Documentation/filesystems/nfs/exporting.rst
+++ b/Documentation/filesystems/nfs/exporting.rst
@@ -154,6 +154,11 @@ struct which has the following members:
to find potential names, and matches inode numbers to find the correct
match.
+ flags
+ Some filesystems may need to be handled differently than others. The
+ export_operations struct also includes a flags field that allows the
+ filesystem to communicate such information to nfsd. See the Export
+ Operations Flags section below for more explanation.
A filehandle fragment consists of an array of 1 or more 4byte words,
together with a one byte "type".
@@ -163,3 +168,50 @@ generated by encode_fh, in which case it will have been padded with
nuls. Rather, the encode_fh routine should choose a "type" which
indicates the decode_fh how much of the filehandle is valid, and how
it should be interpreted.
+
+Export Operations Flags
+-----------------------
+In addition to the operation vector pointers, struct export_operations also
+contains a "flags" field that allows the filesystem to communicate to nfsd
+that it may want to do things differently when dealing with it. The
+following flags are defined:
+
+ EXPORT_OP_NOWCC - disable NFSv3 WCC attributes on this filesystem
+ RFC 1813 recommends that servers always send weak cache consistency
+ (WCC) data to the client after each operation. The server should
+ atomically collect attributes about the inode, do an operation on it,
+ and then collect the attributes afterward. This allows the client to
+ skip issuing GETATTRs in some situations but means that the server
+ is calling vfs_getattr for almost all RPCs. On some filesystems
+ (particularly those that are clustered or networked) this is expensive
+ and atomicity is difficult to guarantee. This flag indicates to nfsd
+ that it should skip providing WCC attributes to the client in NFSv3
+ replies when doing operations on this filesystem. Consider enabling
+ this on filesystems that have an expensive ->getattr inode operation,
+ or when atomicity between pre and post operation attribute collection
+ is impossible to guarantee.
+
+ EXPORT_OP_NOSUBTREECHK - disallow subtree checking on this fs
+ Many NFS operations deal with filehandles, which the server must then
+ vet to ensure that they live inside of an exported tree. When the
+ export consists of an entire filesystem, this is trivial. nfsd can just
+ ensure that the filehandle live on the filesystem. When only part of a
+ filesystem is exported however, then nfsd must walk the ancestors of the
+ inode to ensure that it's within an exported subtree. This is an
+ expensive operation and not all filesystems can support it properly.
+ This flag exempts the filesystem from subtree checking and causes
+ exportfs to get back an error if it tries to enable subtree checking
+ on it.
+
+ EXPORT_OP_CLOSE_BEFORE_UNLINK - always close cached files before unlinking
+ On some exportable filesystems (such as NFS) unlinking a file that
+ is still open can cause a fair bit of extra work. For instance,
+ the NFS client will do a "sillyrename" to ensure that the file
+ sticks around while it's still open. When reexporting, that open
+ file is held by nfsd so we usually end up doing a sillyrename, and
+ then immediately deleting the sillyrenamed file just afterward when
+ the link count actually goes to zero. Sometimes this delete can race
+ with other operations (for instance an rmdir of the parent directory).
+ This flag causes nfsd to close any open files for this inode _before_
+ calling into the vfs to do an unlink or a rename that would replace
+ an existing file.