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Date: Wed, 19 Jan 2011 09:02:59 +1100
Message-ID: <AANLkTikL2CDSWQJ1QH_Y4G-j70Vd=VesNMMnYTmMGHC9@mail.gmail.com>
Subject: Re: [PATCH] fs/dcache: allow __d_obtain_alias() to return unhashed dentries
From: Nick Piggin <npiggin@gmail.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>, Nick Piggin <npiggin@kernel.dk>,
        linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
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Sender: linux-nfs-owner@vger.kernel.org
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On Wed, Jan 19, 2011 at 7:45 AM, J. Bruce Fields <bfields@fieldses.org> wrote:

> Nick Piggin suggested fixing this by allowing d_obtain_alias to return
> the unhashed dentry that is referenced by the filp, instead of making it
> create a new dentry.
>
> Leave __d_find_alias() alone to avoid changing behavior of other
> callers.
>
> Also nfsd doesn't need all the checks of __d_find_alias(); any dentry,
> hashed or unhashed, disconnected or not, should work.
>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
> ?fs/dcache.c | ? 26 ++++++++++++++++++++++++--
> ?1 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 9f493ee..2849258 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1521,6 +1521,28 @@ struct dentry * d_alloc_root(struct inode * root_inode)
> ?}
> ?EXPORT_SYMBOL(d_alloc_root);
>
> +static struct dentry * __d_find_any_alias(struct inode *inode)
> +{
> + ? ? ? struct dentry *alias;
> +
> + ? ? ? if (list_empty(&inode->i_dentry))
> + ? ? ? ? ? ? ? return NULL;
> + ? ? ? alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
> + ? ? ? __dget(alias);
> + ? ? ? return alias;
> +}
> +
> +static struct dentry * d_find_any_alias(struct inode *inode)
> +{
> + ? ? ? struct dentry *de;
> +
> + ? ? ? spin_lock(&inode->i_lock);

Yes, i_dentry/d_alias is protected by i_lock, so it looks fine.