fault-inject: improve build for CONFIG_FAULT_INJECTION=n

The fault-inject.h users across the kernel need to add a lot of #ifdef
CONFIG_FAULT_INJECTION to cater for shortcomings in the header.  Make
fault-inject.h self-contained for CONFIG_FAULT_INJECTION=n, and add stubs
for DECLARE_FAULT_ATTR(), setup_fault_attr(), should_fail_ex(), and
should_fail() to allow removal of conditional compilation.

[akpm@linux-foundation.org: repair fallout from no longer including debugfs.h into fault-inject.h]
[akpm@linux-foundation.org: fix drivers/misc/xilinx_tmr_inject.c]
[akpm@linux-foundation.org: Add debugfs.h inclusion to more files, per Stephen]
Link: https://lkml.kernel.org/r/20240813121237.2382534-1-jani.nikula@intel.com
Fixes: 6ff1cb35 ("[PATCH] fault-injection capabilities infrastructure")
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/gpu/drm/msm/msm_drv.c

@@ -7,6 +7,7 @@
 
 #include <linux/dma-mapping.h>
 #include <linux/fault-inject.h>
+#include <linux/debugfs.h>
 #include <linux/of_address.h>
 #include <linux/uaccess.h>
 

drivers/iommu/iommufd/selftest.c

@@ -7,6 +7,7 @@
 #include <linux/iommu.h>
 #include <linux/xarray.h>
 #include <linux/file.h>
+#include <linux/debugfs.h>
 #include <linux/anon_inodes.h>
 #include <linux/fault-inject.h>
 #include <linux/platform_device.h>

drivers/misc/xilinx_tmr_inject.c

@@ -12,6 +12,7 @@
 #include <asm/xilinx_mb_manager.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/debugfs.h>
 #include <linux/platform_device.h>
 #include <linux/fault-inject.h>
 

drivers/nvme/host/fault_inject.c

@@ -6,6 +6,7 @@
  */
 
 #include <linux/moduleparam.h>
+#include <linux/debugfs.h>
 #include "nvme.h"
 
 static DECLARE_FAULT_ATTR(fail_default_attr);

drivers/ufs/core/ufs-fault-injection.c

@@ -3,6 +3,7 @@
 #include <linux/kconfig.h>
 #include <linux/types.h>
 #include <linux/fault-inject.h>
+#include <linux/debugfs.h>
 #include <linux/module.h>
 #include <ufs/ufshcd.h>
 #include "ufs-fault-injection.h"

include/linux/fault-inject.h

@@ -2,13 +2,17 @@
 #ifndef _LINUX_FAULT_INJECT_H
 #define _LINUX_FAULT_INJECT_H
 
+#include <linux/err.h>
+#include <linux/types.h>
+
+struct dentry;
+struct kmem_cache;
+
 #ifdef CONFIG_FAULT_INJECTION
 
-#include <linux/types.h>
-#include <linux/debugfs.h>
+#include <linux/atomic.h>
 #include <linux/configfs.h>
 #include <linux/ratelimit.h>
-#include <linux/atomic.h>
 
 /*
  * For explanation of the elements of this struct, see
@@ -51,6 +55,28 @@ int setup_fault_attr(struct fault_attr *attr, char *str);
 bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags);
 bool should_fail(struct fault_attr *attr, ssize_t size);
 
+#else /* CONFIG_FAULT_INJECTION */
+
+struct fault_attr {
+};
+
+#define DECLARE_FAULT_ATTR(name) struct fault_attr name = {}
+
+static inline int setup_fault_attr(struct fault_attr *attr, char *str)
+{
+	return 0; /* Note: 0 means error for __setup() handlers! */
+}
+static inline bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
+{
+	return false;
+}
+static inline bool should_fail(struct fault_attr *attr, ssize_t size)
+{
+	return false;
+}
+
+#endif /* CONFIG_FAULT_INJECTION */
+
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 
 struct dentry *fault_create_debugfs_attr(const char *name,
@@ -87,10 +113,6 @@ static inline void fault_config_init(struct fault_config *config,
 
 #endif /* CONFIG_FAULT_INJECTION_CONFIGFS */
 
-#endif /* CONFIG_FAULT_INJECTION */
-
-struct kmem_cache;
-
 #ifdef CONFIG_FAIL_PAGE_ALLOC
 bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order);
 #else

include/linux/mmc/host.h

@@ -10,6 +10,7 @@
 #include <linux/sched.h>
 #include <linux/device.h>
 #include <linux/fault-inject.h>
+#include <linux/debugfs.h>
 
 #include <linux/mmc/core.h>
 #include <linux/mmc/card.h>

include/ufs/ufshcd.h

@@ -17,6 +17,7 @@
 #include <linux/blk-mq.h>
 #include <linux/devfreq.h>
 #include <linux/fault-inject.h>
+#include <linux/debugfs.h>
 #include <linux/msi.h>
 #include <linux/pm_runtime.h>
 #include <linux/dma-direction.h>

kernel/futex/core.c

@@ -34,6 +34,7 @@
 #include <linux/compat.h>
 #include <linux/jhash.h>
 #include <linux/pagemap.h>
+#include <linux/debugfs.h>
 #include <linux/plist.h>
 #include <linux/memblock.h>
 #include <linux/fault-inject.h>

lib/fault-inject.c

@@ -2,6 +2,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/random.h>
+#include <linux/debugfs.h>
 #include <linux/sched.h>
 #include <linux/stat.h>
 #include <linux/types.h>

mm/fail_page_alloc.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/fault-inject.h>
+#include <linux/debugfs.h>
 #include <linux/error-injection.h>
 #include <linux/mm.h>
 

mm/failslab.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/fault-inject.h>
 #include <linux/error-injection.h>
+#include <linux/debugfs.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include "slab.h"