9p: implement i_op->atomic_open()

Add an ->atomic_open implementation which replaces the atomic open+create
operation implemented via ->create.  No functionality is changed.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 137 insertions, 84 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 57ccb7537dae..e8c42ceb89ba 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -712,11 +712,14 @@ error:
 }
 
 /**
- * v9fs_vfs_create - VFS hook to create files
+ * v9fs_vfs_create - VFS hook to create a regular file
+ *
+ * open(.., O_CREAT) is handled in v9fs_vfs_atomic_open().  This is only called
+ * for mknod(2).
+ *
  * @dir: directory inode that is being created
  * @dentry:  dentry that is being deleted
  * @mode: create permissions
- * @nd: path information
  *
  */
 
@@ -724,76 +727,19 @@ static int
 v9fs_vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
                 struct nameidata *nd)
 {
-        int err;
-        u32 perm;
-        int flags;
-        struct file *filp;
-        struct v9fs_inode *v9inode;
-        struct v9fs_session_info *v9ses;
-        struct p9_fid *fid, *inode_fid;
-
-        err = 0;
-        fid = NULL;
-        v9ses = v9fs_inode2v9ses(dir);
-        perm = unixmode2p9mode(v9ses, mode);
-        if (nd)
-                flags = nd->intent.open.flags;
-        else
-                flags = O_RDWR;
+        struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
+        u32 perm = unixmode2p9mode(v9ses, mode);
+        struct p9_fid *fid;
 
-        fid = v9fs_create(v9ses, dir, dentry, NULL, perm,
-                                v9fs_uflags2omode(flags,
-                                                v9fs_proto_dotu(v9ses)));
-        if (IS_ERR(fid)) {
-                err = PTR_ERR(fid);
-                fid = NULL;
-                goto error;
-        }
+        /* P9_OEXCL? */
+        fid = v9fs_create(v9ses, dir, dentry, NULL, perm, P9_ORDWR);
+        if (IS_ERR(fid))
+                return PTR_ERR(fid);
 
         v9fs_invalidate_inode_attr(dir);
-        /* if we are opening a file, assign the open fid to the file */
-        if (nd) {
-                v9inode = V9FS_I(dentry->d_inode);
-                mutex_lock(&v9inode->v_mutex);
-                if (v9ses->cache && !v9inode->writeback_fid &&
-                    ((flags & O_ACCMODE) != O_RDONLY)) {
-                        /*
-                         * clone a fid and add it to writeback_fid
-                         * we do it during open time instead of
-                         * page dirty time via write_begin/page_mkwrite
-                         * because we want write after unlink usecase
-                         * to work.
-                         */
-                        inode_fid = v9fs_writeback_fid(dentry);
-                        if (IS_ERR(inode_fid)) {
-                                err = PTR_ERR(inode_fid);
-                                mutex_unlock(&v9inode->v_mutex);
-                                goto error;
-                        }
-                        v9inode->writeback_fid = (void *) inode_fid;
-                }
-                mutex_unlock(&v9inode->v_mutex);
-                filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
-                if (IS_ERR(filp)) {
-                        err = PTR_ERR(filp);
-                        goto error;
-                }
-
-                filp->private_data = fid;
-#ifdef CONFIG_9P_FSCACHE
-                if (v9ses->cache)
-                        v9fs_cache_inode_set_cookie(dentry->d_inode, filp);
-#endif
-        } else
-                p9_client_clunk(fid);
+        p9_client_clunk(fid);
 
         return 0;
-
-error:
-        if (fid)
-                p9_client_clunk(fid);
-
-        return err;
 }
 
 /**
@@ -910,6 +856,93 @@ error:
         return ERR_PTR(result);
 }
 
+static struct file *
+v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
+                     struct opendata *od, unsigned flags, umode_t mode,
+                     bool *created)
+{
+        int err;
+        u32 perm;
+        struct file *filp;
+        struct v9fs_inode *v9inode;
+        struct v9fs_session_info *v9ses;
+        struct p9_fid *fid, *inode_fid;
+        struct dentry *res = NULL;
+
+        if (d_unhashed(dentry)) {
+                res = v9fs_vfs_lookup(dir, dentry, NULL);
+                if (IS_ERR(res))
+                        return ERR_CAST(res);
+
+                if (res)
+                        dentry = res;
+        }
+
+        /* Only creates */
+        if (!(flags & O_CREAT) || dentry->d_inode) {
+                finish_no_open(od, res);
+                return NULL;
+        }
+
+        err = 0;
+        fid = NULL;
+        v9ses = v9fs_inode2v9ses(dir);
+        perm = unixmode2p9mode(v9ses, mode);
+        fid = v9fs_create(v9ses, dir, dentry, NULL, perm,
+                                v9fs_uflags2omode(flags,
+                                                v9fs_proto_dotu(v9ses)));
+        if (IS_ERR(fid)) {
+                err = PTR_ERR(fid);
+                fid = NULL;
+                goto error;
+        }
+
+        v9fs_invalidate_inode_attr(dir);
+        v9inode = V9FS_I(dentry->d_inode);
+        mutex_lock(&v9inode->v_mutex);
+        if (v9ses->cache && !v9inode->writeback_fid &&
+            ((flags & O_ACCMODE) != O_RDONLY)) {
+                /*
+                 * clone a fid and add it to writeback_fid
+                 * we do it during open time instead of
+                 * page dirty time via write_begin/page_mkwrite
+                 * because we want write after unlink usecase
+                 * to work.
+                 */
+                inode_fid = v9fs_writeback_fid(dentry);
+                if (IS_ERR(inode_fid)) {
+                        err = PTR_ERR(inode_fid);
+                        mutex_unlock(&v9inode->v_mutex);
+                        goto error;
+                }
+                v9inode->writeback_fid = (void *) inode_fid;
+        }
+        mutex_unlock(&v9inode->v_mutex);
+        filp = finish_open(od, dentry, generic_file_open);
+        if (IS_ERR(filp)) {
+                err = PTR_ERR(filp);
+                goto error;
+        }
+
+        filp->private_data = fid;
+#ifdef CONFIG_9P_FSCACHE
+        if (v9ses->cache)
+                v9fs_cache_inode_set_cookie(dentry->d_inode, filp);
+#endif
+
+        *created = true;
+out:
+        dput(res);
+        return filp;
+
+error:
+        if (fid)
+                p9_client_clunk(fid);
+
+        filp = ERR_PTR(err);
+        goto out;
+}
+
 /**
  * v9fs_vfs_unlink - VFS unlink hook to delete an inode
  * @i:  inode that is being unlinked
@@ -1488,6 +1521,7 @@ out:
 static const struct inode_operations v9fs_dir_inode_operations_dotu = {
         .create = v9fs_vfs_create,
         .lookup = v9fs_vfs_lookup,
+        .atomic_open = v9fs_vfs_atomic_open,
         .symlink = v9fs_vfs_symlink,
         .link = v9fs_vfs_link,
         .unlink = v9fs_vfs_unlink,
@@ -1502,6 +1536,7 @@ static const struct inode_operations v9fs_dir_inode_operations_dotu = {
 static const struct inode_operations v9fs_dir_inode_operations = {
         .create = v9fs_vfs_create,
         .lookup = v9fs_vfs_lookup,
+        .atomic_open = v9fs_vfs_atomic_open,
         .unlink = v9fs_vfs_unlink,
         .mkdir = v9fs_vfs_mkdir,
         .rmdir = v9fs_vfs_rmdir,
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index e3dd2a1e2bfc..a354fe2cb234 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -230,7 +230,6 @@ int v9fs_open_to_dotl_flags(int flags)
  * @dir: directory inode that is being created
  * @dentry:  dentry that is being deleted
  * @mode: create permissions
- * @nd: path information
  *
  */
 
@@ -238,9 +237,16 @@ static int
 v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
                 struct nameidata *nd)
 {
+        return v9fs_vfs_mknod_dotl(dir, dentry, omode, 0);
+}
+
+static struct file *
+v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
+                          struct opendata *od, unsigned flags, umode_t omode,
+                          bool *created)
+{
         int err = 0;
         gid_t gid;
-        int flags;
         umode_t mode;
         char *name = NULL;
         struct file *filp;
@@ -251,19 +257,25 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
         struct p9_fid *dfid, *ofid, *inode_fid;
         struct v9fs_session_info *v9ses;
         struct posix_acl *pacl = NULL, *dacl = NULL;
+        struct dentry *res = NULL;
 
-        v9ses = v9fs_inode2v9ses(dir);
-        if (nd)
-                flags = nd->intent.open.flags;
-        else {
-                /*
-                 * create call without LOOKUP_OPEN is due
-                 * to mknod of regular files. So use mknod
-                 * operation.
-                 */
-                return v9fs_vfs_mknod_dotl(dir, dentry, omode, 0);
+        if (d_unhashed(dentry)) {
+                res = v9fs_vfs_lookup(dir, dentry, NULL);
+                if (IS_ERR(res))
+                        return ERR_CAST(res);
+
+                if (res)
+                        dentry = res;
+        }
+
+        /* Only creates */
+        if (!(flags & O_CREAT) || dentry->d_inode) {
+                finish_no_open(od, res);
+                return NULL;
         }
 
+        v9ses = v9fs_inode2v9ses(dir);
+
         name = (char *) dentry->d_name.name;
         p9_debug(P9_DEBUG_VFS, "name:%s flags:0x%x mode:0x%hx\n",
                  name, flags, omode);
@@ -272,7 +284,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
         if (IS_ERR(dfid)) {
                 err = PTR_ERR(dfid);
                 p9_debug(P9_DEBUG_VFS, "fid lookup failed %d\n", err);
-                return err;
+                goto err_return;
         }
 
         /* clone a fid to use for creation */
@@ -280,7 +292,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
         if (IS_ERR(ofid)) {
                 err = PTR_ERR(ofid);
                 p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
-                return err;
+                goto err_return;
         }
 
         gid = v9fs_get_fsgid_for_create(dir);
@@ -345,7 +357,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
         }
         mutex_unlock(&v9inode->v_mutex);
         /* Since we are opening a file, assign the open fid to the file */
-        filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
+        filp = finish_open(od, dentry, generic_file_open);
         if (IS_ERR(filp)) {
                 err = PTR_ERR(filp);
                 goto err_clunk_old_fid;
@@ -355,7 +367,10 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, umode_t omode,
         if (v9ses->cache)
                 v9fs_cache_inode_set_cookie(inode, filp);
 #endif
-        return 0;
+        *created = true;
+out:
+        dput(res);
+        return filp;
 
 error:
         if (fid)
@@ -364,7 +379,9 @@ err_clunk_old_fid:
         if (ofid)
                 p9_client_clunk(ofid);
         v9fs_set_create_acl(NULL, &dacl, &pacl);
-        return err;
+err_return:
+        filp = ERR_PTR(err);
+        goto out;
 }
 
 /**
@@ -982,6 +999,7 @@ out:
 
 const struct inode_operations v9fs_dir_inode_operations_dotl = {
         .create = v9fs_vfs_create_dotl,
+        .atomic_open = v9fs_vfs_atomic_open_dotl,
         .lookup = v9fs_vfs_lookup,
         .link = v9fs_vfs_link_dotl,
         .symlink = v9fs_vfs_symlink_dotl,