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    Subject[PATCH v3 003/110] ovl: rearrange ovl_follow_link to it doesn't need to call ->put_link
    Date
    From: NeilBrown <neilb@suse.de>

    ovl_follow_link current calls ->put_link on an error path.
    However ->put_link is about to change in a way that it will be
    impossible to call it from ovl_follow_link.

    So rearrange the code to avoid the need for that error path.
    Specifically: move the kmalloc() call before the ->follow_link()
    call to the subordinate filesystem.

    Signed-off-by: NeilBrown <neilb@suse.de>
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    ---
    fs/overlayfs/inode.c | 25 ++++++++++++-------------
    1 file changed, 12 insertions(+), 13 deletions(-)

    diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
    index 04f1248..1b4b9c5e 100644
    --- a/fs/overlayfs/inode.c
    +++ b/fs/overlayfs/inode.c
    @@ -145,6 +145,7 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
    void *ret;
    struct dentry *realdentry;
    struct inode *realinode;
    + struct ovl_link_data *data = NULL;

    realdentry = ovl_dentry_real(dentry);
    realinode = realdentry->d_inode;
    @@ -152,25 +153,23 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
    if (WARN_ON(!realinode->i_op->follow_link))
    return ERR_PTR(-EPERM);

    - ret = realinode->i_op->follow_link(realdentry, nd);
    - if (IS_ERR(ret))
    - return ret;
    -
    if (realinode->i_op->put_link) {
    - struct ovl_link_data *data;
    -
    data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
    - if (!data) {
    - realinode->i_op->put_link(realdentry, nd, ret);
    + if (!data)
    return ERR_PTR(-ENOMEM);
    - }
    data->realdentry = realdentry;
    - data->cookie = ret;
    + }

    - return data;
    - } else {
    - return NULL;
    + ret = realinode->i_op->follow_link(realdentry, nd);
    + if (IS_ERR(ret)) {
    + kfree(data);
    + return ret;
    }
    +
    + if (data)
    + data->cookie = ret;
    +
    + return data;
    }

    static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
    --
    2.1.4


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