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Documentation: Add missing documentation for EXPORT_OP flags 

The commits that introduced these flags neglected to update the
Documentation/filesystems/nfs/exporting.rst file.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2023-08-25 15:04:23 -04:00
parent 899525e892
commit b38a6023da
1 changed files with 26 additions and 0 deletions
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26
Documentation/filesystems/nfs/exporting.rst
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@ -215,3 +215,29 @@ 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.