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    Subject[PATCH v3 11/21] __dentry_kill(): get consistent rules for victim's refcount
    Date
    Currently we call it with refcount equal to 1 when called from
    dentry_kill(); all other callers have it equal to 0.

    Make it always be called with zero refcount; on this step we
    just decrement it before the calls in dentry_kill(). That is
    safe, since all places that care about the value of refcount
    either do that under ->d_lock or hold a reference to dentry
    in question. Either is sufficient to prevent observing a
    dentry immediately prior to __dentry_kill() getting called
    from dentry_kill().

    Reviewed-by: Christian Brauner <brauner@kernel.org>
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    ---
    fs/dcache.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/fs/dcache.c b/fs/dcache.c
    index 2e74f3f2ce2e..b527db8e5901 100644
    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -729,6 +729,7 @@ static struct dentry *dentry_kill(struct dentry *dentry)
    goto slow_positive;
    }
    }
    + dentry->d_lockref.count--;
    __dentry_kill(dentry);
    return parent;

    @@ -741,6 +742,7 @@ static struct dentry *dentry_kill(struct dentry *dentry)
    if (unlikely(dentry->d_lockref.count != 1)) {
    dentry->d_lockref.count--;
    } else if (likely(!retain_dentry(dentry))) {
    + dentry->d_lockref.count--;
    __dentry_kill(dentry);
    return parent;
    } else {
    --
    2.39.2
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