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    SubjectRe: [PATCH 12/25] sysfs: Introduce sysfs_rename_mutex
    Hello, Eric.

    Eric W. Biederman wrote:
    > Looking carefully at the rename code we have a subtle dependency
    > that the structure of sysfs not change while we are performing
    > a rename. If the parent directory of the object we are renaming
    > changes while the rename is being performed nasty things could
    > happen when we go to release our locks.
    >
    > So introduce a sysfs_rename_mutex to prevent this highly
    > unlikely theoretical issue.

    Yeah, it's a theoretical issue. Rename/move implementation has always
    depended on the parent structure not changing beneath it, but it's nice
    to tighten up loose ends.

    > +DEFINE_MUTEX(sysfs_rename_mutex);

    Probably doesn't really matter but wouldn't a rwsem fit better?

    > @@ -774,7 +775,7 @@ static struct dentry *__sysfs_get_dentry(struct super_block *sb, struct sysfs_di
    > * down from there looking up dentry for each step.
    > *
    > * LOCKING:
    > - * Kernel thread context (may sleep)
    > + * mutex_lock(sysfs_rename_mutex)

    LOCKING describes what locks should be held when entering the function,
    so proper description would be something like...

    Kernel thread context, grabs sysfs_rename_mutex

    Thanks.

    --
    tejun
    -
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