[PATCH 06/64] fscache: Introduce new driver

From: David Howells
Date: Mon Nov 29 2021 - 09:27:25 EST

Introduce basic skeleton of the new, rewritten fscache driver.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
---

fs/Makefile | 1
fs/fscache/Kconfig | 39 +++++++++
fs/fscache/Makefile | 12 +++
fs/fscache/internal.h | 183 ++++++++++++++++++++++++++++++++++++++++
fs/fscache/main.c | 65 ++++++++++++++
fs/fscache/proc.c | 42 +++++++++
fs/fscache/stats.c | 22 +++++
include/linux/fscache-cache.h | 2
include/linux/fscache.h | 6 +
include/trace/events/fscache.h | 49 +++++++++++
10 files changed, 420 insertions(+), 1 deletion(-)
create mode 100644 fs/fscache/Makefile
create mode 100644 fs/fscache/internal.h
create mode 100644 fs/fscache/main.c
create mode 100644 fs/fscache/proc.c
create mode 100644 fs/fscache/stats.c
create mode 100644 include/trace/events/fscache.h

diff --git a/fs/Makefile b/fs/Makefile
index 23ddd0803d14..290815f3fd31 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_DLM) += dlm/

# Do not add any filesystems before this line
obj-$(CONFIG_NETFS_SUPPORT) += netfs/
+obj-$(CONFIG_FSCACHE) += fscache/
obj-$(CONFIG_REISERFS_FS) += reiserfs/
obj-$(CONFIG_EXT4_FS) += ext4/
# We place ext4 before ext2 so that clean ext3 root fs's do NOT mount using the
diff --git a/fs/fscache/Kconfig b/fs/fscache/Kconfig
index 6440484d9461..76316c4a3fb7 100644
--- a/fs/fscache/Kconfig
+++ b/fs/fscache/Kconfig
@@ -1,4 +1,43 @@
# SPDX-License-Identifier: GPL-2.0-only

+config FSCACHE
+ tristate "General filesystem local caching manager"
+ select NETFS_SUPPORT
+ help
+ This option enables a generic filesystem caching manager that can be
+ used by various network and other filesystems to cache data locally.
+ Different sorts of caches can be plugged in, depending on the
+ resources available.
+
+ See Documentation/filesystems/caching/fscache.rst for more information.
+
+config FSCACHE_STATS
+ bool "Gather statistical information on local caching"
+ depends on FSCACHE && PROC_FS
+ select NETFS_STATS
+ help
+ This option causes statistical information to be gathered on local
+ caching and exported through file:
+
+ /proc/fs/fscache/stats
+
+ The gathering of statistics adds a certain amount of overhead to
+ execution as there are a quite a few stats gathered, and on a
+ multi-CPU system these may be on cachelines that keep bouncing
+ between CPUs. On the other hand, the stats are very useful for
+ debugging purposes. Saying 'Y' here is recommended.
+
+ See Documentation/filesystems/caching/fscache.rst for more information.
+
+config FSCACHE_DEBUG
+ bool "Debug FS-Cache"
+ depends on FSCACHE
+ help
+ This permits debugging to be dynamically enabled in the local caching
+ management module. If this is set, the debugging output may be
+ enabled by setting bits in /sys/modules/fscache/parameter/debug.
+
+ See Documentation/filesystems/caching/fscache.rst for more information.
+
config FSCACHE_OLD_API
bool
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
new file mode 100644
index 000000000000..f9722de32247
--- /dev/null
+++ b/fs/fscache/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for general filesystem caching code
+#
+
+fscache-y := \
+ main.o
+
+fscache-$(CONFIG_PROC_FS) += proc.o
+fscache-$(CONFIG_FSCACHE_STATS) += stats.o
+
+obj-$(CONFIG_FSCACHE) := fscache.o
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
new file mode 100644
index 000000000000..ea52f8594a77
--- /dev/null
+++ b/fs/fscache/internal.h
@@ -0,0 +1,183 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Internal definitions for FS-Cache
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) "FS-Cache: " fmt
+
+#include <linux/slab.h>
+#include <linux/fscache-cache.h>
+#include <trace/events/fscache.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+
+/*
+ * main.c
+ */
+extern unsigned fscache_debug;
+
+/*
+ * proc.c
+ */
+#ifdef CONFIG_PROC_FS
+extern int __init fscache_proc_init(void);
+extern void fscache_proc_cleanup(void);
+#else
+#define fscache_proc_init() (0)
+#define fscache_proc_cleanup() do {} while (0)
+#endif
+
+/*
+ * stats.c
+ */
+#ifdef CONFIG_FSCACHE_STATS
+
+static inline void fscache_stat(atomic_t *stat)
+{
+ atomic_inc(stat);
+}
+
+static inline void fscache_stat_d(atomic_t *stat)
+{
+ atomic_dec(stat);
+}
+
+#define __fscache_stat(stat) (stat)
+
+int fscache_stats_show(struct seq_file *m, void *v);
+#else
+
+#define __fscache_stat(stat) (NULL)
+#define fscache_stat(stat) do {} while (0)
+#define fscache_stat_d(stat) do {} while (0)
+#endif
+
+
+/*****************************************************************************/
+/*
+ * debug tracing
+ */
+#define dbgprintk(FMT, ...) \
+ printk("[%-6.6s] "FMT"\n", current->comm, ##__VA_ARGS__)
+
+#define kenter(FMT, ...) dbgprintk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__)
+
+#define kjournal(FMT, ...) no_printk(FMT, ##__VA_ARGS__)
+
+#ifdef __KDEBUG
+#define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__)
+#define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__)
+#define _debug(FMT, ...) kdebug(FMT, ##__VA_ARGS__)
+
+#elif defined(CONFIG_FSCACHE_DEBUG)
+#define _enter(FMT, ...) \
+do { \
+ if (__do_kdebug(ENTER)) \
+ kenter(FMT, ##__VA_ARGS__); \
+} while (0)
+
+#define _leave(FMT, ...) \
+do { \
+ if (__do_kdebug(LEAVE)) \
+ kleave(FMT, ##__VA_ARGS__); \
+} while (0)
+
+#define _debug(FMT, ...) \
+do { \
+ if (__do_kdebug(DEBUG)) \
+ kdebug(FMT, ##__VA_ARGS__); \
+} while (0)
+
+#else
+#define _enter(FMT, ...) no_printk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define _leave(FMT, ...) no_printk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define _debug(FMT, ...) no_printk(FMT, ##__VA_ARGS__)
+#endif
+
+/*
+ * determine whether a particular optional debugging point should be logged
+ * - we need to go through three steps to persuade cpp to correctly join the
+ * shorthand in FSCACHE_DEBUG_LEVEL with its prefix
+ */
+#define ____do_kdebug(LEVEL, POINT) \
+ unlikely((fscache_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)
+
+#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
+
+/*
+ * assertions
+ */
+#if 1 /* defined(__KDEBUGALL) */
+
+#define ASSERT(X) \
+do { \
+ if (unlikely(!(X))) { \
+ pr_err("\n"); \
+ pr_err("Assertion failed\n"); \
+ BUG(); \
+ } \
+} while (0)
+
+#define ASSERTCMP(X, OP, Y) \
+do { \
+ if (unlikely(!((X) OP (Y)))) { \
+ pr_err("\n"); \
+ pr_err("Assertion failed\n"); \
+ pr_err("%lx " #OP " %lx is false\n", \
+ (unsigned long)(X), (unsigned long)(Y)); \
+ BUG(); \
+ } \
+} while (0)
+
+#define ASSERTIF(C, X) \
+do { \
+ if (unlikely((C) && !(X))) { \
+ pr_err("\n"); \
+ pr_err("Assertion failed\n"); \
+ BUG(); \
+ } \
+} while (0)
+
+#define ASSERTIFCMP(C, X, OP, Y) \
+do { \
+ if (unlikely((C) && !((X) OP (Y)))) { \
+ pr_err("\n"); \
+ pr_err("Assertion failed\n"); \
+ pr_err("%lx " #OP " %lx is false\n", \
+ (unsigned long)(X), (unsigned long)(Y)); \
+ BUG(); \
+ } \
+} while (0)
+
+#else
+
+#define ASSERT(X) do {} while (0)
+#define ASSERTCMP(X, OP, Y) do {} while (0)
+#define ASSERTIF(C, X) do {} while (0)
+#define ASSERTIFCMP(C, X, OP, Y) do {} while (0)
+
+#endif /* assert or not */
diff --git a/fs/fscache/main.c b/fs/fscache/main.c
new file mode 100644
index 000000000000..819de2ee1276
--- /dev/null
+++ b/fs/fscache/main.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* General filesystem local caching manager
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#define FSCACHE_DEBUG_LEVEL CACHE
+#include <linux/module.h>
+#include <linux/init.h>
+#define CREATE_TRACE_POINTS
+#include "internal.h"
+
+MODULE_DESCRIPTION("FS Cache Manager");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+unsigned fscache_debug;
+module_param_named(debug, fscache_debug, uint,
+ S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(fscache_debug,
+ "FS-Cache debugging mask");
+
+struct workqueue_struct *fscache_wq;
+EXPORT_SYMBOL(fscache_wq);
+
+/*
+ * initialise the fs caching module
+ */
+static int __init fscache_init(void)
+{
+ int ret = -ENOMEM;
+
+ fscache_wq = alloc_workqueue("fscache", WQ_UNBOUND | WQ_FREEZABLE, 0);
+ if (!fscache_wq)
+ goto error_wq;
+
+ ret = fscache_proc_init();
+ if (ret < 0)
+ goto error_proc;
+
+ pr_notice("Loaded\n");
+ return 0;
+
+error_proc:
+ destroy_workqueue(fscache_wq);
+error_wq:
+ return ret;
+}
+
+fs_initcall(fscache_init);
+
+/*
+ * clean up on module removal
+ */
+static void __exit fscache_exit(void)
+{
+ _enter("");
+
+ fscache_proc_cleanup();
+ destroy_workqueue(fscache_wq);
+ pr_notice("Unloaded\n");
+}
+
+module_exit(fscache_exit);
diff --git a/fs/fscache/proc.c b/fs/fscache/proc.c
new file mode 100644
index 000000000000..b28003d7d63f
--- /dev/null
+++ b/fs/fscache/proc.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* FS-Cache statistics viewing interface
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#define FSCACHE_DEBUG_LEVEL CACHE
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+/*
+ * initialise the /proc/fs/fscache/ directory
+ */
+int __init fscache_proc_init(void)
+{
+ if (!proc_mkdir("fs/fscache", NULL))
+ goto error_dir;
+
+#ifdef CONFIG_FSCACHE_STATS
+ if (!proc_create_single("fs/fscache/stats", S_IFREG | 0444, NULL,
+ fscache_stats_show))
+ goto error;
+#endif
+
+ return 0;
+
+error:
+ remove_proc_entry("fs/fscache", NULL);
+error_dir:
+ return -ENOMEM;
+}
+
+/*
+ * clean up the /proc/fs/fscache/ directory
+ */
+void fscache_proc_cleanup(void)
+{
+ remove_proc_entry("fs/fscache", NULL);
+}
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
new file mode 100644
index 000000000000..bd92f93e1680
--- /dev/null
+++ b/fs/fscache/stats.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* FS-Cache statistics
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#define FSCACHE_DEBUG_LEVEL CACHE
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+/*
+ * display the general statistics
+ */
+int fscache_stats_show(struct seq_file *m, void *v)
+{
+ seq_puts(m, "FS-Cache statistics\n");
+
+ netfs_stats_show(m);
+ return 0;
+}
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 47f21a53ac4b..d6910a913918 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -16,4 +16,6 @@

#include <linux/fscache.h>

+extern struct workqueue_struct *fscache_wq;
+
#endif /* _LINUX_FSCACHE_CACHE_H */
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 0364a4ca16f6..1cf90c252aac 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -1,7 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */
/* General filesystem caching interface
*
- * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@xxxxxxxxxx)
*
* NOTE!!! See:
@@ -18,9 +18,13 @@
#include <linux/netfs.h>

#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+#define __fscache_available (1)
+#define fscache_available() (1)
#define fscache_cookie_valid(cookie) (cookie)
#define fscache_cookie_enabled(cookie) (cookie)
#else
+#define __fscache_available (0)
+#define fscache_available() (0)
#define fscache_cookie_valid(cookie) (0)
#define fscache_cookie_enabled(cookie) (0)
#endif
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
new file mode 100644
index 000000000000..fe214c5cc87f
--- /dev/null
+++ b/include/trace/events/fscache.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* FS-Cache tracepoints
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM fscache
+
+#if !defined(_TRACE_FSCACHE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FSCACHE_H
+
+#include <linux/fscache.h>
+#include <linux/tracepoint.h>
+
+/*
+ * Define enums for tracing information.
+ */
+#ifndef __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
+#define __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
+
+#endif
+
+/*
+ * Declare tracing information enums and their string mappings for display.
+ */
+
+/*
+ * Export enum symbols via userspace.
+ */
+#undef EM
+#undef E_
+#define EM(a, b) TRACE_DEFINE_ENUM(a);
+#define E_(a, b) TRACE_DEFINE_ENUM(a);
+
+/*
+ * Now redefine the EM() and E_() macros to map the enums to the strings that
+ * will be printed in the output.
+ */
+#undef EM
+#undef E_
+#define EM(a, b) { a, b },
+#define E_(a, b) { a, b }
+
+
+#endif /* _TRACE_FSCACHE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>