[PATCH] NFSD: Fix nfs4_delegation_stat()

[cel@kernel.org]

From: Chuck Lever <chuck.lever@oracle.com>

The xfstests workflow on NFSv4.2 exhausts the capacity of both the
main and scratch devices (backed by xfs) about half-way through
each test run.

Deleting all visible files on both devices frees only a little bit
of space. The test exports can be unshared but not unmounted
(EBUSY). Looks like unlinked but still open files, maybe.

Bisected to commit c495f65ad2ff ("nfsd: fix initial getattr on write
delegation")

Ensure nfsd_file objects acquired by find_rw_file() are released.

Fixes: c495f65ad2ff ("nfsd: fix initial getattr on write delegation")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs4state.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

Tested, problem no longer reproducible. I intend to squash this into
c495f65ad2ff.

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 252297b98a2e..cb5a9ab451c5 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5920,6 +5920,7 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
 {
 	struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);
 	struct path path;
+	int rc;
 
 	if (!nf)
 		return false;
@@ -5927,11 +5928,12 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
 	path.mnt = currentfh->fh_export->ex_path.mnt;
 	path.dentry = file_dentry(nf->nf_file);
 
-	if (vfs_getattr(&path, stat,
-			(STATX_SIZE | STATX_CTIME | STATX_CHANGE_COOKIE),
-			AT_STATX_SYNC_AS_STAT))
-		return false;
-	return true;
+	rc = vfs_getattr(&path, stat,
+			 (STATX_SIZE | STATX_CTIME | STATX_CHANGE_COOKIE),
+			 AT_STATX_SYNC_AS_STAT);
+
+	nfsd_file_put(nf);
+	return rc == 0;
 }
 
 /*
-- 
2.45.2