[PATCH] netfs: Restore selective debug mask handling

[Karl Mehltretter <kmehltretter@gmail.com>]

The netfs debug macros test only whether netfs_debug is nonzero.
Consequently, selecting one debug point enables every entry, exit and
general debug message.

Documentation/filesystems/caching/fscache.rst and the NETFS_DEBUG
Kconfig help still describe /sys/module/netfs/parameters/debug as a
bitmask of per-stream function entry, exit and general debugging
points, and the fscache_*.c files still define FSCACHE_DEBUG_LEVEL,
but nothing has decoded either since the mask handling was dropped
when FS-Cache was folded into netfs.

Restore the per-level and per-point mask decoding.  Files that do not
define FSCACHE_DEBUG_LEVEL, which includes the netfs core, fall under
the cache management stream, the same default the FS-Cache macros had.

Fixes: 915cd30cdea8 ("netfs, fscache: Combine fscache with netfs")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 fs/netfs/internal.h | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 420ee7b26580f..425c73b7e77b4 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -468,6 +468,32 @@ void fscache_create_volume(struct fscache_volume *volume, bool wait);
 #define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
 #define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__)
 
+#define FSCACHE_DEBUG_CACHE	0
+#define FSCACHE_DEBUG_COOKIE	1
+#define FSCACHE_DEBUG_OBJECT	2
+#define FSCACHE_DEBUG_OPERATION	3
+
+#define FSCACHE_POINT_ENTER	1
+#define FSCACHE_POINT_LEAVE	2
+#define FSCACHE_POINT_DEBUG	4
+
+#ifndef FSCACHE_DEBUG_LEVEL
+#define FSCACHE_DEBUG_LEVEL CACHE
+#endif
+
+/*
+ * Determine whether a particular optional debugging point should be logged.
+ * Three levels of indirection are needed to expand FSCACHE_DEBUG_LEVEL before
+ * joining it with its prefix.
+ */
+#define ____do_kdebug(LEVEL, POINT) \
+	unlikely(netfs_debug & \
+		 (FSCACHE_POINT_##POINT << (FSCACHE_DEBUG_ ## LEVEL * 3)))
+#define ___do_kdebug(LEVEL, POINT) \
+	____do_kdebug(LEVEL, POINT)
+#define __do_kdebug(POINT) \
+	___do_kdebug(FSCACHE_DEBUG_LEVEL, POINT)
+
 #ifdef __KDEBUG
 #define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__)
 #define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__)
@@ -476,19 +502,19 @@ void fscache_create_volume(struct fscache_volume *volume, bool wait);
 #elif defined(CONFIG_NETFS_DEBUG)
 #define _enter(FMT, ...)			\
 do {						\
-	if (netfs_debug)			\
+	if (__do_kdebug(ENTER))			\
 		kenter(FMT, ##__VA_ARGS__);	\
 } while (0)
 
 #define _leave(FMT, ...)			\
 do {						\
-	if (netfs_debug)			\
+	if (__do_kdebug(LEAVE))			\
 		kleave(FMT, ##__VA_ARGS__);	\
 } while (0)
 
 #define _debug(FMT, ...)			\
 do {						\
-	if (netfs_debug)			\
+	if (__do_kdebug(DEBUG))			\
 		kdebug(FMT, ##__VA_ARGS__);	\
 } while (0)
 
-- 
2.53.0