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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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