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Diffstat (limited to 'Documentation/filesystems/nfs/exporting.rst')
| -rw-r--r-- | Documentation/filesystems/nfs/exporting.rst | 42 |
1 files changed, 36 insertions, 6 deletions
diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst index 0e98edd353b5..f04ce1215a03 100644 --- a/Documentation/filesystems/nfs/exporting.rst +++ b/Documentation/filesystems/nfs/exporting.rst @@ -122,12 +122,9 @@ are exportable by setting the s_export_op field in the struct super_block. This field must point to a "struct export_operations" struct which has the following members: - encode_fh (optional) - Takes a dentry and creates a filehandle fragment which can later be used - to find or create a dentry for the same object. The default - implementation creates a filehandle fragment that encodes a 32bit inode - and generation number for the inode encoded, and if necessary the - same information for the parent. + encode_fh (mandatory) + Takes a dentry and creates a filehandle fragment which may later be used + to find or create a dentry for the same object. fh_to_dentry (mandatory) Given a filehandle fragment, this should find the implied object and @@ -215,3 +212,36 @@ following flags are defined: 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. + + EXPORT_OP_REMOTE_FS - Backing storage for this filesystem is remote + PF_LOCAL_THROTTLE exists for loopback NFSD, where a thread needs to + write to one bdi (the final bdi) in order to free up writes queued + to another bdi (the client bdi). Such threads get a private balance + of dirty pages so that dirty pages for the client bdi do not imact + the daemon writing to the final bdi. For filesystems whose durable + storage is not local (such as exported NFS filesystems), this + constraint has negative consequences. EXPORT_OP_REMOTE_FS enables + an export to disable writeback throttling. + + EXPORT_OP_NOATOMIC_ATTR - Filesystem does not update attributes atomically + EXPORT_OP_NOATOMIC_ATTR indicates that the exported filesystem + cannot provide the semantics required by the "atomic" boolean in + NFSv4's change_info4. This boolean indicates to a client whether the + returned before and after change attributes were obtained atomically + with the respect to the requested metadata operation (UNLINK, + OPEN/CREATE, MKDIR, etc). + + EXPORT_OP_FLUSH_ON_CLOSE - Filesystem flushes file data on close(2) + On most filesystems, inodes can remain under writeback after the + file is closed. NFSD relies on client activity or local flusher + threads to handle writeback. Certain filesystems, such as NFS, flush + all of an inode's dirty data on last close. Exports that behave this + way should set EXPORT_OP_FLUSH_ON_CLOSE so that NFSD knows to skip + waiting for writeback when closing such files. + + EXPORT_OP_ASYNC_LOCK - Indicates a capable filesystem to do async lock + requests from lockd. Only set EXPORT_OP_ASYNC_LOCK if the filesystem has + it's own ->lock() functionality as core posix_lock_file() implementation + has no async lock request handling yet. For more information about how to + indicate an async lock request from a ->lock() file_operations struct, see + fs/locks.c and comment for the function vfs_lock_file(). |