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


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