do_last: unify may_open() call and everyting after it

We have a bunch of diverging codepaths in do_last(); some of
them converge, but the case of having to create a new file
duplicates large part of common tail of the rest and exits
separately.  Massage them so that they could be merged.

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

diff --git a/fs/namei.c b/fs/namei.c
index def63e7..6384477 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2114,7 +2114,10 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                            const struct open_flags *op, const char *pathname)
 {
        struct dentry *dir = nd->path.dentry;
+       int open_flag = op->open_flag;
        int will_truncate;
+       int want_write = 0;
+       int skip_perm = 0;
        struct file *filp;
        struct inode *inode;
        int error;
@@ -2138,7 +2141,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                if (error)
                        goto exit;
                audit_inode(pathname, nd->path.dentry);
-               if (op->open_flag & O_CREAT) {
+               if (open_flag & O_CREAT) {
                        error = -EISDIR;
                        goto exit;
                }
@@ -2152,7 +2155,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                goto ok;
        }
 
-       if (!(op->open_flag & O_CREAT)) {
+       if (!(open_flag & O_CREAT)) {
                if (nd->last.name[nd->last.len])
                        nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
                /* we _can_ be in RCU mode here */
@@ -2230,28 +2233,15 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                error = mnt_want_write(nd->path.mnt);
                if (error)
                        goto exit_mutex_unlock;
-               error = __open_namei_create(nd, path, op->open_flag, op->mode);
-               if (error) {
-                       mnt_drop_write(nd->path.mnt);
+               want_write = 1;
+               will_truncate = 0;
+               error = __open_namei_create(nd, path, open_flag, op->mode);
+               if (error)
                        goto exit;
-               }
                /* Don't check for write permission, don't truncate */
-               error = may_open(&nd->path, 0, op->open_flag & ~O_TRUNC);
-               if (error) {
-                       mnt_drop_write(nd->path.mnt);
-                       goto exit;
-               }
-               filp = nameidata_to_filp(nd);
-               mnt_drop_write(nd->path.mnt);
-               path_put(&nd->path);
-               if (!IS_ERR(filp)) {
-                       error = ima_file_check(filp, op->acc_mode);
-                       if (error) {
-                               fput(filp);
-                               filp = ERR_PTR(error);
-                       }
-               }
-               return filp;
+               open_flag &= ~O_TRUNC;
+               skip_perm = 1;
+               goto common;
        }
 
        /*
@@ -2261,7 +2251,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
        audit_inode(pathname, path->dentry);
 
        error = -EEXIST;
-       if (op->open_flag & O_EXCL)
+       if (open_flag & O_EXCL)
                goto exit_dput;
 
        error = follow_managed(path, nd->flags);
@@ -2281,18 +2271,17 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
        if (S_ISDIR(nd->inode->i_mode))
                goto exit;
 ok:
-       will_truncate = open_will_truncate(op->open_flag, nd->path.dentry->d_inode);
+       will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);
        if (will_truncate) {
                error = mnt_want_write(nd->path.mnt);
                if (error)
                        goto exit;
+               want_write = 1;
        }
-       error = may_open(&nd->path, op->acc_mode, op->open_flag);
-       if (error) {
-               if (will_truncate)
-                       mnt_drop_write(nd->path.mnt);
+common:
+       error = may_open(&nd->path, skip_perm ? 0 : op->acc_mode, open_flag);
+       if (error)
                goto exit;
-       }
        filp = nameidata_to_filp(nd);
        if (!IS_ERR(filp)) {
                error = ima_file_check(filp, op->acc_mode);
@@ -2310,12 +2299,8 @@ ok:
                        }
                }
        }
-       /*
-        * It is now safe to drop the mnt write
-        * because the filp has had a write taken
-        * on its behalf.
-        */
-       if (will_truncate)
+out:
+       if (want_write)
                mnt_drop_write(nd->path.mnt);
        path_put(&nd->path);
        return filp;
@@ -2325,8 +2310,8 @@ exit_mutex_unlock:
 exit_dput:
        path_put_conditional(path, nd);
 exit:
-       path_put(&nd->path);
-       return ERR_PTR(error);
+       filp = ERR_PTR(error);
+       goto out;
 }
 
 static struct file *path_openat(int dfd, const char *pathname,