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>

1 files changed, 22 insertions, 37 deletions

diff --git a/fs/namei.c b/fs/namei.c
index def63e7c058d..63844776484c 100644
--- 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,