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    SubjectRe: [PATCH 14/25] sysfs: Don't use lookup_one_len_kern
    On Tue, Aug 07, 2007 at 03:23:57PM -0600, Eric W. Biederman wrote:
    >
    > Upon inspection it appears that there is no looking of the
    > inode mutex in lookup_one_len_kern and we aren't calling
    > it with the inode mutex and that is wrong.
    >
    > So this patch rolls our own dcache insertion function that
    > does exactly what we need it to do. As it turns out this
    > is pretty trivial to do and it makes the code easier to
    > audit.
    >
    > Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    > ---
    > fs/sysfs/dir.c | 41 +++++++++++++++++++++++++++++++++++++++--
    > 1 files changed, 39 insertions(+), 2 deletions(-)
    >
    > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
    > index a9bdb12..1d53c2a 100644
    > --- a/fs/sysfs/dir.c
    > +++ b/fs/sysfs/dir.c
    > @@ -765,6 +765,44 @@ static struct dentry *__sysfs_get_dentry(struct super_block *sb, struct sysfs_di
    > return dentry;
    > }
    >
    > +static struct dentry *sysfs_add_dentry(struct dentry *parent, struct sysfs_dirent *sd)
    > +{
    > + struct qstr name;
    > + struct dentry *dentry;
    > + struct inode *inode;
    > +
    > + mutex_lock(&parent->d_inode->i_mutex);
    > + mutex_lock(&sysfs_mutex);
    > + dentry = ERR_PTR(-EINVAL);
    > + if (parent->d_fsdata != sd->s_parent)
    > + goto out;
    > +
    > + name.name = sd->s_name;
    > + name.len = strlen(sd->s_name);
    > + dentry = d_hash_and_lookup(parent, &name);
    > + if (dentry)
    > + goto out;
    > +
    > + dentry = d_alloc(parent, &name);
    > + if (!dentry) {
    > + dentry = ERR_PTR(-ENOMEM);
    > + goto out;
    > + }
    > +
    > + inode = sysfs_get_inode(sd);
    > + if (!inode) {
    > + dput(dentry);
    > + dentry = ERR_PTR(-ENOMEM);
    > + goto out;
    > + }
    > + d_instantiate(dentry, inode);
    > + sysfs_attach_dentry(sd, dentry);
    > +out:
    > + mutex_unlock(&sysfs_mutex);
    > + mutex_unlock(&parent->d_inode->i_mutex);
    > + return dentry;
    > +}

    This is virtually identical to

    mutex_lock(&parent_dentry->d_inode->i_mutex);
    dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
    strlen(cur->s_name));
    mutex_unlock(&parent_dentry->d_inode->i_mutex);

    right? I don't think we need to duplicate the code here. Or is it
    needed for later multi-sb thing?

    --
    tejun
    -
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      Last update: 2007-08-08 10:41    [W:0.028 / U:93.936 seconds]
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