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>

1 files changed, 5 insertions, 8 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1dbcf8888f1..6e8ecb6e021 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;
 }