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    Subject[PATCH 15/17] fold handle_mounts() into step_into()
    Date
    From: Al Viro <viro@zeniv.linux.org.uk>

    The following is true:
    * calls of handle_mounts() and step_into() are always
    paired in sequences like
    err = handle_mounts(nd, dentry, &path, &inode, &seq);
    if (unlikely(err < 0))
    return err;
    err = step_into(nd, &path, flags, inode, seq);
    * in all such sequences path is uninitialized before and
    unused after this pair of calls
    * in all such sequences inode and seq are unused afterwards.

    So the call of handle_mounts() can be shifted inside step_into(),
    turning 'path' into a local variable in the combined function.

    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    ---
    fs/namei.c | 41 +++++++++++++++--------------------------
    1 file changed, 15 insertions(+), 26 deletions(-)

    diff --git a/fs/namei.c b/fs/namei.c
    index 44634643475d..6c28b969f4d1 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -1721,31 +1721,35 @@ enum {WALK_FOLLOW = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
    * so we keep a cache of "no, this doesn't need follow_link"
    * for the common case.
    */
    -static inline int step_into(struct nameidata *nd, struct path *path,
    - int flags, struct inode *inode, unsigned seq)
    +static int step_into(struct nameidata *nd, int flags,
    + struct dentry *dentry, struct inode *inode, unsigned seq)
    {
    + struct path path;
    + int err = handle_mounts(nd, dentry, &path, &inode, &seq);
    +
    + if (err < 0)
    + return err;
    if (!(flags & WALK_MORE) && nd->depth)
    put_link(nd);
    - if (likely(!d_is_symlink(path->dentry)) ||
    + if (likely(!d_is_symlink(path.dentry)) ||
    !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW) ||
    flags & WALK_NOFOLLOW) {
    /* not a symlink or should not follow */
    - path_to_nameidata(path, nd);
    + path_to_nameidata(&path, nd);
    nd->inode = inode;
    nd->seq = seq;
    return 0;
    }
    /* make sure that d_is_symlink above matches inode */
    if (nd->flags & LOOKUP_RCU) {
    - if (read_seqcount_retry(&path->dentry->d_seq, seq))
    + if (read_seqcount_retry(&path.dentry->d_seq, seq))
    return -ECHILD;
    }
    - return pick_link(nd, path, inode, seq);
    + return pick_link(nd, &path, inode, seq);
    }

    static int walk_component(struct nameidata *nd, int flags)
    {
    - struct path path;
    struct dentry *dentry;
    struct inode *inode;
    unsigned seq;
    @@ -1769,11 +1773,7 @@ static int walk_component(struct nameidata *nd, int flags)
    if (IS_ERR(dentry))
    return PTR_ERR(dentry);
    }
    -
    - err = handle_mounts(nd, dentry, &path, &inode, &seq);
    - if (unlikely(err < 0))
    - return err;
    - return step_into(nd, &path, flags, inode, seq);
    + return step_into(nd, flags, dentry, inode, seq);
    }

    /*
    @@ -2222,17 +2222,10 @@ static inline int lookup_last(struct nameidata *nd)

    static int handle_lookup_down(struct nameidata *nd)
    {
    - struct path path;
    - struct inode *inode = nd->inode;
    - unsigned seq = nd->seq;
    - int err;
    -
    if (!(nd->flags & LOOKUP_RCU))
    dget(nd->path.dentry);
    - err = handle_mounts(nd, nd->path.dentry, &path, &inode, &seq);
    - if (unlikely(err < 0))
    - return err;
    - return step_into(nd, &path, WALK_NOFOLLOW, inode, seq);
    + return step_into(nd, WALK_NOFOLLOW,
    + nd->path.dentry, nd->inode, nd->seq);
    }

    /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
    @@ -3149,7 +3142,6 @@ static int do_last(struct nameidata *nd,
    int acc_mode = op->acc_mode;
    unsigned seq;
    struct inode *inode;
    - struct path path;
    struct dentry *dentry;
    int error;

    @@ -3247,10 +3239,7 @@ static int do_last(struct nameidata *nd,
    }

    finish_lookup:
    - error = handle_mounts(nd, dentry, &path, &inode, &seq);
    - if (unlikely(error < 0))
    - return error;
    - error = step_into(nd, &path, 0, inode, seq);
    + error = step_into(nd, 0, dentry, inode, seq);
    if (unlikely(error))
    return error;

    --
    2.20.1
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