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    Subject[PATCH 05/16] vfs: make follow_link check RCU safe
    Date
    From: Miklos Szeredi <mszeredi@suse.cz>

    This will allow this code to be used in RCU mode.

    Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
    ---
    fs/namei.c | 12 ++++++++++--
    1 files changed, 10 insertions(+), 2 deletions(-)

    diff --git a/fs/namei.c b/fs/namei.c
    index f21ddb3..a3a0fa1 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -2203,6 +2203,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
    int acc_mode = op->acc_mode;
    struct file *filp;
    struct inode *inode;
    + int symlink_ok = 0;
    int error;

    nd->flags &= ~LOOKUP_PARENT;
    @@ -2234,7 +2235,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
    }

    if (!(open_flag & O_CREAT)) {
    - int symlink_ok = 0;
    if (nd->last.name[nd->last.len])
    nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
    if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
    @@ -2365,8 +2365,16 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
    if (!inode)
    goto exit_dput;

    - if (inode->i_op->follow_link)
    + if (should_follow_link(inode, !symlink_ok)) {
    + if (nd->flags & LOOKUP_RCU) {
    + if (unlikely(unlazy_walk(nd, path->dentry))) {
    + error = -ECHILD;
    + goto exit;
    + }
    + }
    + BUG_ON(inode != path->dentry->d_inode);
    return NULL;
    + }

    path_to_nameidata(path, nd);
    nd->inode = inode;
    --
    1.7.7


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