NFSD: Close cached file handles when revoking export state

When NFSD_CMD_UNLOCK_EXPORT revokes NFSv4 state for an export path,
GC-managed nfsd_file entries for files under that path may remain
in the file cache.  These cached handles hold the underlying
filesystem busy, preventing a subsequent unmount.

Add nfsd_file_close_export(), which walks the nfsd_file hash table
and closes GC-eligible entries whose underlying file resides on the
same filesystem and is a descendant of the export path.  Because
nfsd_file entries do not carry an export reference, the ancestry
check uses is_subdir() on the file's dentry.  False positives --
closing a cached handle that did not originate from the target
export -- are harmless; the handle is simply reopened on the next
access.

The handler calls nfsd_file_close_export() before revoking NFSv4
state, mirroring the order used by NFSD_CMD_UNLOCK_FILESYSTEM
(which cancels copies and releases NLM locks before revoking
state).  Both calls run under nfsd_mutex.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

0 files changed, 0 insertions, 0 deletions