[PATCH v3 1/2] nfsd: add a runtime switch for disabling delegated timestamps

[Jeff Layton <jlayton@kernel.org>]

The delegated timestamp code seems to be working well enough now that we
want to make it always be built in. In the event that there are problems
though, we still want to be able to disable them for debugging purposes.
Add a switch to debugfs to enable them at runtime.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/debugfs.c   | 4 ++++
 fs/nfsd/nfs4state.c | 8 ++++++++
 fs/nfsd/nfsd.h      | 1 +
 3 files changed, 13 insertions(+)

diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c
index 7f44689e0a53edbfd6ade9dda6af4052976a65d3..386fd1c54f5277fd9b9544caa5220e234915264d 100644
--- a/fs/nfsd/debugfs.c
+++ b/fs/nfsd/debugfs.c
@@ -140,4 +140,8 @@ void nfsd_debugfs_init(void)
 
 	debugfs_create_file("io_cache_write", 0644, nfsd_top_dir, NULL,
 			    &nfsd_io_cache_write_fops);
+#ifdef CONFIG_NFSD_V4
+	debugfs_create_bool("delegated_timestamps", 0644, nfsd_top_dir,
+			    &nfsd_delegts_enabled);
+#endif
 }
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 583c13b5aaf3cd12a87c7aae62fe6a8223368f55..2251ff43aac8ef8a3d01d7094d40f9b2604763d6 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -76,6 +76,8 @@ static const stateid_t close_stateid = {
 
 static u64 current_sessionid = 1;
 
+bool nfsd_delegts_enabled __read_mostly = true;
+
 #define ZERO_STATEID(stateid) (!memcmp((stateid), &zero_stateid, sizeof(stateid_t)))
 #define ONE_STATEID(stateid)  (!memcmp((stateid), &one_stateid, sizeof(stateid_t)))
 #define CURRENT_STATEID(stateid) (!memcmp((stateid), &currentstateid, sizeof(stateid_t)))
@@ -6046,8 +6048,14 @@ nfsd4_verify_setuid_write(struct nfsd4_open *open, struct nfsd_file *nf)
 }
 
 #ifdef CONFIG_NFSD_V4_DELEG_TIMESTAMPS
+/*
+ * Timestamp delegation was introduced in RFC7862. Runtime switch for disabling
+ * this feature is /sys/kernel/debug/nfsd/delegated_timestamps.
+ */
 static bool nfsd4_want_deleg_timestamps(const struct nfsd4_open *open)
 {
+	if (!nfsd_delegts_enabled)
+		return false;
 	return open->op_deleg_want & OPEN4_SHARE_ACCESS_WANT_DELEG_TIMESTAMPS;
 }
 #else /* CONFIG_NFSD_V4_DELEG_TIMESTAMPS */
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index a2e35a4fa105380c2d99cb0865003e0f7f4a8e8d..7c009f07c90b50d7074695d4665a2eca85140eda 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -160,6 +160,7 @@ static inline void nfsd_debugfs_exit(void) {}
 #endif
 
 extern bool nfsd_disable_splice_read __read_mostly;
+extern bool nfsd_delegts_enabled __read_mostly;
 
 enum {
 	/* Any new NFSD_IO enum value must be added at the end */

-- 
2.52.0