do_last(): simplify the liveness analysis past finish_open_created

Don't mess with got_write there - it is guaranteed to be false on
entry and it will be set true if and only if we decide to go for
truncation and manage to get write access for that.

Don't carry acc_mode through the entire thing - it's only used
in that part.  And don't bother with gotos in there - compiler is
quite capable of optimizing that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namei.c b/fs/namei.c
index c85fdfd6b33d475602a7dcc2d4c2355903b8bd4b..8cdf8ef41194d4eae3e9dcb3ef67607563b98a6f 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3122,9 +3122,9 @@ static const char *do_last(struct nameidata *nd,
        kuid_t dir_uid = nd->inode->i_uid;
        umode_t dir_mode = nd->inode->i_mode;
        int open_flag = op->open_flag;
-       bool will_truncate = (open_flag & O_TRUNC) != 0;
+       bool do_truncate;
        bool got_write = false;
-       int acc_mode = op->acc_mode;
+       int acc_mode;
        unsigned seq;
        struct inode *inode;
        struct dentry *dentry;
@@ -3243,36 +3243,30 @@ finish_open:
                return ERR_PTR(-ENOTDIR);
 
 finish_open_created:
+       do_truncate = false;
+       acc_mode = op->acc_mode;
        if (file->f_mode & FMODE_CREATED) {
                /* Don't check for write permission, don't truncate */
                open_flag &= ~O_TRUNC;
-               will_truncate = false;
                acc_mode = 0;
-       } else if (!d_is_reg(nd->path.dentry)) {
-               will_truncate = false;
-       }
-       if (will_truncate) {
+       } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
                error = mnt_want_write(nd->path.mnt);
                if (error)
                        return ERR_PTR(error);
-               got_write = true;
+               do_truncate = true;
        }
        error = may_open(&nd->path, acc_mode, open_flag);
-       if (error)
-               goto out;
-       if (!(file->f_mode & FMODE_OPENED))
+       if (!error && !(file->f_mode & FMODE_OPENED))
                error = vfs_open(&nd->path, file);
-       if (error)
-               goto out;
-       error = ima_file_check(file, op->acc_mode);
-       if (!error && will_truncate)
+       if (!error)
+               error = ima_file_check(file, op->acc_mode);
+       if (!error && do_truncate)
                error = handle_truncate(file);
-out:
        if (unlikely(error > 0)) {
                WARN_ON(1);
                error = -EINVAL;
        }
-       if (got_write)
+       if (do_truncate)
                mnt_drop_write(nd->path.mnt);
        return ERR_PTR(error);
 }