linux-dev/Documentation/filesystems/nfs, branch master

Documentation: Add an explanation of NFSv4 client identifiers

2022-05-17T19:33:21Z

To enable NFSv4 to work correctly, NFSv4 client identifiers have to be globally unique and persistent over client reboots. We believe that in many cases, a good default identifier can be chosen and set when a client system is imaged. Because there are many different ways a system can be imaged, provide an explanation of how NFSv4 client identifiers and principals can be set by install scripts and imaging tools. Additional cases, such as NFSv4 clients running in containers, also need unique and persistent identifiers. The Linux NFS community sets forth this explanation to aid those who create and manage container environments. Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker

nfs: reexport documentation

2021-09-21T21:51:47Z

We've supported reexport for a while but documentation is limited. This is mainly a simplified version of the text I wrote for the linux-nfs wiki at https://wiki.linux-nfs.org/wiki/index.php/NFS_re-export. Signed-off-by: J. Bruce Fields

nfsd: close cached files prior to a REMOVE or RENAME that would replace target

2020-12-09T14:39:38Z

It's not uncommon for some workloads to do a bunch of I/O to a file and delete it just afterward. If knfsd has a cached open file however, then the file may still be open when the dentry is unlinked. If the underlying filesystem is nfs, then that could trigger it to do a sillyrename. On a REMOVE or RENAME scan the nfsd_file cache for open files that correspond to the inode, and proactively unhash and put their references. This should prevent any delete-on-last-close activity from occurring, solely due to knfsd's open file cache. This must be done synchronously though so we use the variants that call flush_delayed_fput. There are deadlock possibilities if you call flush_delayed_fput while holding locks, however. In the case of nfsd_rename, we don't even do the lookups of the dentries to be renamed until we've locked for rename. Once we've figured out what the target dentry is for a rename, check to see whether there are cached open files associated with it. If there are, then unwind all of the locking, close them all, and then reattempt the rename. None of this is really necessary for "typical" filesystems though. It's mostly of use for NFS, so declare a new export op flag and use that to determine whether to close the files beforehand. Signed-off-by: Jeff Layton Signed-off-by: Lance Shelton Signed-off-by: Trond Myklebust Signed-off-by: Chuck Lever

nfsd: allow filesystems to opt out of subtree checking

2020-12-09T14:39:38Z

When we start allowing NFS to be reexported, then we have some problems when it comes to subtree checking. In principle, we could allow it, but it would mean encoding parent info in the filehandles and there may not be enough space for that in a NFSv3 filehandle. To enforce this at export upcall time, we add a new export_ops flag that declares the filesystem ineligible for subtree checking. Signed-off-by: Jeff Layton Signed-off-by: Lance Shelton Signed-off-by: Trond Myklebust Signed-off-by: Chuck Lever

nfsd: add a new EXPORT_OP_NOWCC flag to struct export_operations

2020-12-09T14:39:38Z

With NFSv3 nfsd will always attempt to send along WCC data to the client. This generally involves saving off the in-core inode information prior to doing the operation on the given filehandle, and then issuing a vfs_getattr to it after the op. Some filesystems (particularly clustered or networked ones) have an expensive ->getattr inode operation. Atomicity is also often difficult or impossible to guarantee on such filesystems. For those, we're best off not trying to provide WCC information to the client at all, and to simply allow it to poll for that information as needed with a GETATTR RPC. This patch adds a new flags field to struct export_operations, and defines a new EXPORT_OP_NOWCC flag that filesystems can use to indicate that nfsd should not attempt to provide WCC info in NFSv3 replies. It also adds a blurb about the new flags field and flag to the exporting documentation. The server will also now skip collecting this information for NFSv2 as well, since that info is never used there anyway. Note that this patch does not add this flag to any filesystem export_operations structures. This was originally developed to allow reexporting nfs via nfsd. Other filesystems may want to consider enabling this flag too. It's hard to tell however which ones have export operations to enable export via knfsd and which ones mostly rely on them for open-by-filehandle support, so I'm leaving that up to the individual maintainers to decide. I am cc'ing the relevant lists for those filesystems that I think may want to consider adding this though. Cc: HPDD-discuss@lists.01.org Cc: ceph-devel@vger.kernel.org Cc: cluster-devel@redhat.com Cc: fuse-devel@lists.sourceforge.net Cc: ocfs2-devel@oss.oracle.com Signed-off-by: Jeff Layton Signed-off-by: Lance Shelton Signed-off-by: Trond Myklebust Signed-off-by: Chuck Lever

Documentation: update RPCSEC_GSSv3 RFC link

2020-09-25T22:01:27Z

This draft is an official RFC now. Signed-off-by: J. Bruce Fields

Replace HTTP links with HTTPS ones: Documentation/filesystems

2020-06-26T17:14:12Z

Rationale: Reduces attack surface on kernel devs opening the links for MITM as HTTPS traffic is much harder to manipulate. Deterministic algorithm: For each file: If not .svg: For each line: If doesn't contain `\bxmlns\b`: For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`: If both the HTTP and HTTPS versions return 200 OK and serve the same content: Replace HTTP with HTTPS. Signed-off-by: Alexander A. Klimov Link: https://lore.kernel.org/r/20200621133552.46371-1-grandmaster@al2klimov.de Signed-off-by: Jonathan Corbet

Documentation: nfs: knfsd-stats: convert to ReST

2020-02-13T18:21:35Z

Convert knfsd-stats.txt to ReST. Content remains mostly the same. Signed-off-by: Daniel W. S. Almeida Link: https://lore.kernel.org/r/20200129044917.566906-6-dwlsalmeida@gmail.com Signed-off-by: Jonathan Corbet

Documentation: nfs: nfs41-server: convert to ReST

2020-02-13T18:21:31Z

Convert nfs41-server.txt to ReST. ASCII tables were converted to ReST grid table format. Signed-off-by: Daniel W. S. Almeida Link: https://lore.kernel.org/r/20200129044917.566906-5-dwlsalmeida@gmail.com Signed-off-by: Jonathan Corbet

Documentation: nfs: rpc-server-gss: convert to ReST

2020-02-13T18:21:28Z

Convert rpc-server-gss.txt to ReST. Content remains mostly unchanged. Signed-off-by: Daniel W. S. Almeida Link: https://lore.kernel.org/r/20200129044917.566906-4-dwlsalmeida@gmail.com Signed-off-by: Jonathan Corbet