fault-injection: add ability to export fault_attr in arbitrary directory

init_fault_attr_dentries() is used to export fault_attr via debugfs.
But it can only export it in debugfs root directory.

Per Forlin is working on mmc_fail_request which adds support to inject
data errors after a completed host transfer in MMC subsystem.

The fault_attr for mmc_fail_request should be defined per mmc host and
export it in debugfs directory per mmc host like
/sys/kernel/debug/mmc0/mmc_fail_request.

init_fault_attr_dentries() doesn't help for mmc_fail_request.  So this
introduces fault_create_debugfs_attr() which is able to create a
directory in the arbitrary directory and replace
init_fault_attr_dentries().

[akpm@linux-foundation.org: extraneous semicolon, per Randy]
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Tested-by: Per Forlin <per.forlin@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

7 files changed, 33 insertions, 46 deletions

diff --git a/Documentation/fault-injection/fault-injection.txt b/Documentation/fault-injection/fault-injection.txt
index 7be15e44d481..82a5d250d75e 100644
--- a/Documentation/fault-injection/fault-injection.txt
+++ b/Documentation/fault-injection/fault-injection.txt
@@ -143,8 +143,7 @@ o provide a way to configure fault attributes
   failslab, fail_page_alloc, and fail_make_request use this way.
   Helper functions:
 
-        init_fault_attr_dentries(entries, attr, name);
-        void cleanup_fault_attr_dentries(entries);
+        fault_create_debugfs_attr(name, parent, attr);
 
 - module parameters
 
diff --git a/block/blk-core.c b/block/blk-core.c
index b850bedad229..b627558c461f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1368,8 +1368,10 @@ static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
 
 static int __init fail_make_request_debugfs(void)
 {
-        return init_fault_attr_dentries(&fail_make_request,
-                                        "fail_make_request");
+        struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
+                                                NULL, &fail_make_request);
+
+        return IS_ERR(dir) ? PTR_ERR(dir) : 0;
 }
 
 late_initcall(fail_make_request_debugfs);
diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index 4f0c06c7a338..780354888958 100644
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -28,7 +28,10 @@ int blk_should_fake_timeout(struct request_queue *q)
 
 static int __init fail_io_timeout_debugfs(void)
 {
-        return init_fault_attr_dentries(&fail_io_timeout, "fail_io_timeout");
+        struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
+                                                NULL, &fail_io_timeout);
+
+        return IS_ERR(dir) ? PTR_ERR(dir) : 0;
 }
 
 late_initcall(fail_io_timeout_debugfs);
diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
index 3ff060ac7810..c6f996f2abb6 100644
--- a/include/linux/fault-inject.h
+++ b/include/linux/fault-inject.h
@@ -25,10 +25,6 @@ struct fault_attr {
         unsigned long reject_end;
 
         unsigned long count;
-
-#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
-        struct dentry *dir;
-#endif
 };
 
 #define FAULT_ATTR_INITIALIZER {                                \
@@ -45,19 +41,15 @@ bool should_fail(struct fault_attr *attr, ssize_t size);
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 
-int init_fault_attr_dentries(struct fault_attr *attr, const char *name);
-void cleanup_fault_attr_dentries(struct fault_attr *attr);
+struct dentry *fault_create_debugfs_attr(const char *name,
+                        struct dentry *parent, struct fault_attr *attr);
 
 #else /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 
-static inline int init_fault_attr_dentries(struct fault_attr *attr,
-                                          const char *name)
-{
-        return -ENODEV;
-}
-
-static inline void cleanup_fault_attr_dentries(struct fault_attr *attr)
+static inline struct dentry *fault_create_debugfs_attr(const char *name,
+                        struct dentry *parent, struct fault_attr *attr)
 {
+        return ERR_PTR(-ENODEV);
 }
 
 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 2577b121c7c1..f193b7796449 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -197,21 +197,15 @@ static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
         return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 }
 
-void cleanup_fault_attr_dentries(struct fault_attr *attr)
-{
-        debugfs_remove_recursive(attr->dir);
-}
-
-int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
+struct dentry *fault_create_debugfs_attr(const char *name,
+                        struct dentry *parent, struct fault_attr *attr)
 {
         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
         struct dentry *dir;
 
-        dir = debugfs_create_dir(name, NULL);
+        dir = debugfs_create_dir(name, parent);
         if (!dir)
-                return -ENOMEM;
-
-        attr->dir = dir;
+                return ERR_PTR(-ENOMEM);
 
         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
                 goto fail;
@@ -243,11 +237,11 @@ int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
 
 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 
-        return 0;
+        return dir;
 fail:
-        debugfs_remove_recursive(attr->dir);
+        debugfs_remove_recursive(dir);
 
-        return -ENOMEM;
+        return ERR_PTR(-ENOMEM);
 }
 
 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
diff --git a/mm/failslab.c b/mm/failslab.c
index 1ce58c201dca..0dd7b8fec71c 100644
--- a/mm/failslab.c
+++ b/mm/failslab.c
@@ -34,23 +34,23 @@ __setup("failslab=", setup_failslab);
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 static int __init failslab_debugfs_init(void)
 {
+        struct dentry *dir;
         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
-        int err;
 
-        err = init_fault_attr_dentries(&failslab.attr, "failslab");
-        if (err)
-                return err;
+        dir = fault_create_debugfs_attr("failslab", NULL, &failslab.attr);
+        if (IS_ERR(dir))
+                return PTR_ERR(dir);
 
-        if (!debugfs_create_bool("ignore-gfp-wait", mode, failslab.attr.dir,
+        if (!debugfs_create_bool("ignore-gfp-wait", mode, dir,
                                 &failslab.ignore_gfp_wait))
                 goto fail;
-        if (!debugfs_create_bool("cache-filter", mode, failslab.attr.dir,
+        if (!debugfs_create_bool("cache-filter", mode, dir,
                                 &failslab.cache_filter))
                 goto fail;
 
         return 0;
 fail:
-        cleanup_fault_attr_dentries(&failslab.attr);
+        debugfs_remove_recursive(dir);
 
         return -ENOMEM;
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1dbcf8888f14..6e8ecb6e021c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1409,14 +1409,11 @@ static int __init fail_page_alloc_debugfs(void)
 {
         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
         struct dentry *dir;
-        int err;
 
-        err = init_fault_attr_dentries(&fail_page_alloc.attr,
-                                       "fail_page_alloc");
-        if (err)
-                return err;
-
-        dir = fail_page_alloc.attr.dir;
+        dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
+                                        &fail_page_alloc.attr);
+        if (IS_ERR(dir))
+                return PTR_ERR(dir);
 
         if (!debugfs_create_bool("ignore-gfp-wait", mode, dir,
                                 &fail_page_alloc.ignore_gfp_wait))
@@ -1430,7 +1427,7 @@ static int __init fail_page_alloc_debugfs(void)
 
         return 0;
 fail:
-        cleanup_fault_attr_dentries(&fail_page_alloc.attr);
+        debugfs_remove_recursive(dir);
 
         return -ENOMEM;
 }