[PATCH 5.15 071/106] init: Initialize noop_backing_dev_info early

Greg Kroah-Hartman
2022-06-20T13:25:49Z

From: Jan Kara <jack@suse.cz>

[ Upstream commit 4bca7e80b6455772b4bf3f536dcbc19aac424d6a ]

noop_backing_dev_info is used by superblocks of various
pseudofilesystems such as kdevtmpfs. After commit 10e14073107d
("writeback: Fix inode->i_io_list not be protected by inode->i_lock
error") this broke because __mark_inode_dirty() started to access more
fields from noop_backing_dev_info and this led to crashes inside
locked_inode_to_wb_and_lock_list() called from __mark_inode_dirty().
Fix the problem by initializing noop_backing_dev_info before the
filesystems get mounted.

Fixes: 10e14073107d ("writeback: Fix inode->i_io_list not be protected by inode->i_lock error")
Reported-and-tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reported-and-tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/base/init.c | 2 ++
include/linux/backing-dev.h | 2 ++
mm/backing-dev.c | 11 ++---------
3 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/base/init.c b/drivers/base/init.c
index a9f57c22fb9e..dab8aa5d2888 100644
--- a/drivers/base/init.c
+++ b/drivers/base/init.c
@@ -8,6 +8,7 @@
#include <linux/init.h>
#include <linux/memory.h>
#include <linux/of.h>
+#include <linux/backing-dev.h>

#include "base.h"

@@ -20,6 +21,7 @@
void __init driver_init(void)
{
/* These are the core pieces */
+ bdi_init(&noop_backing_dev_info);
devtmpfs_init();
devices_init();
buses_init();
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index ac7f231b8825..eed9a98eae0d 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -121,6 +121,8 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);

extern struct backing_dev_info noop_backing_dev_info;

+int bdi_init(struct backing_dev_info *bdi);
+
/**
* writeback_in_progress - determine whether there is writeback in progress
* @wb: bdi_writeback of interest
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 02ff66f86358..02c9d5c7276e 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -229,20 +229,13 @@ static __init int bdi_class_init(void)
}
postcore_initcall(bdi_class_init);

-static int bdi_init(struct backing_dev_info *bdi);
-
static int __init default_bdi_init(void)
{
- int err;
-
bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
WQ_SYSFS, 0);
if (!bdi_wq)
return -ENOMEM;
-
- err = bdi_init(&noop_backing_dev_info);
-
- return err;
+ return 0;
}
subsys_initcall(default_bdi_init);

@@ -784,7 +777,7 @@ static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)

#endif /* CONFIG_CGROUP_WRITEBACK */

-static int bdi_init(struct backing_dev_info *bdi)
+int bdi_init(struct backing_dev_info *bdi)
{
int ret;

--
2.35.1