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SubjectRe: [PATCH 01/17] MTD: create lockless versions of {get,put}_mtd_device This will be used to resolve deadlock in block translation layer.
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On Tue, 2010-02-09 at 18:57 +0200, Maxim Levitsky wrote:
> These functions can be used as long as we don't need access to global mtd table, but have
> a pointer to the mtd device.
>
> Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
> ---
> drivers/mtd/mtdcore.c | 60 ++++++++++++++++++++++++++++++----------------
> include/linux/mtd/mtd.h | 3 +-
> 2 files changed, 41 insertions(+), 22 deletions(-)

> +int __get_mtd_device(struct mtd_info *mtd)
> +{
> + int err;
> +
> + if (!try_module_get(mtd->owner))
> + return -ENODEV;
> +
> + if (mtd->get_device) {
> +
> + err = mtd->get_device(mtd);
> +
> + if (err) {
> + module_put(mtd->owner);
> + return err;
> + }
> + }
> + mtd->usecount++;
> + return 0;
> }

> +void __put_mtd_device(struct mtd_info *mtd)
> +{
> + --mtd->usecount;
> + BUG_ON(mtd->usecount < 0);
> +
> if (mtd->put_device)
> mtd->put_device(mtd);
>
> module_put(mtd->owner);
> }

That's racy, use kref.



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