fuse: return correct dentry for ->mkdir

fuse already uses d_splice_alias() to ensure an appropriate dentry is
found for a newly created dentry.  Now that ->mkdir can return that
dentry we do so.

This requires changing create_new_entry() to return a dentry and
handling that change in all callers.

Note that when create_new_entry() is asked to create anything other than
a directory we can be sure it will NOT return an alternate dentry as
d_splice_alias() only returns an alternate dentry for directories.
So we don't need to check for that case when passing one the result.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/174112490070.33508.15852253149143067890@noble.neil.brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 5bb65f38bfb810f45ab14469068b951ecde20b78..a130b8bbdeb71d2eba76895045c63497a0654f82 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -781,9 +781,9 @@ no_open:
 /*
  * Code shared between mknod, mkdir, symlink and link
  */
-static int create_new_entry(struct mnt_idmap *idmap, struct fuse_mount *fm,
-                           struct fuse_args *args, struct inode *dir,
-                           struct dentry *entry, umode_t mode)
+static struct dentry *create_new_entry(struct mnt_idmap *idmap, struct fuse_mount *fm,
+                                      struct fuse_args *args, struct inode *dir,
+                                      struct dentry *entry, umode_t mode)
 {
        struct fuse_entry_out outarg;
        struct inode *inode;
@@ -792,11 +792,11 @@ static int create_new_entry(struct mnt_idmap *idmap, struct fuse_mount *fm,
        struct fuse_forget_link *forget;
 
        if (fuse_is_bad(dir))
-               return -EIO;
+               return ERR_PTR(-EIO);
 
        forget = fuse_alloc_forget();
        if (!forget)
-               return -ENOMEM;
+               return ERR_PTR(-ENOMEM);
 
        memset(&outarg, 0, sizeof(outarg));
        args->nodeid = get_node_id(dir);
@@ -826,29 +826,43 @@ static int create_new_entry(struct mnt_idmap *idmap, struct fuse_mount *fm,
                          &outarg.attr, ATTR_TIMEOUT(&outarg), 0, 0);
        if (!inode) {
                fuse_queue_forget(fm->fc, forget, outarg.nodeid, 1);
-               return -ENOMEM;
+               return ERR_PTR(-ENOMEM);
        }
        kfree(forget);
 
        d_drop(entry);
        d = d_splice_alias(inode, entry);
        if (IS_ERR(d))
-               return PTR_ERR(d);
+               return d;
 
-       if (d) {
+       if (d)
                fuse_change_entry_timeout(d, &outarg);
-               dput(d);
-       } else {
+       else
                fuse_change_entry_timeout(entry, &outarg);
-       }
        fuse_dir_changed(dir);
-       return 0;
+       return d;
 
  out_put_forget_req:
        if (err == -EEXIST)
                fuse_invalidate_entry(entry);
        kfree(forget);
-       return err;
+       return ERR_PTR(err);
+}
+
+static int create_new_nondir(struct mnt_idmap *idmap, struct fuse_mount *fm,
+                            struct fuse_args *args, struct inode *dir,
+                            struct dentry *entry, umode_t mode)
+{
+       /*
+        * Note that when creating anything other than a directory we
+        * can be sure create_new_entry() will NOT return an alternate
+        * dentry as d_splice_alias() only returns an alternate dentry
+        * for directories.  So we don't need to check for that case
+        * when passing back the result.
+        */
+       WARN_ON_ONCE(S_ISDIR(mode));
+
+       return PTR_ERR(create_new_entry(idmap, fm, args, dir, entry, mode));
 }
 
 static int fuse_mknod(struct mnt_idmap *idmap, struct inode *dir,
@@ -871,7 +885,7 @@ static int fuse_mknod(struct mnt_idmap *idmap, struct inode *dir,
        args.in_args[0].value = &inarg;
        args.in_args[1].size = entry->d_name.len + 1;
        args.in_args[1].value = entry->d_name.name;
-       return create_new_entry(idmap, fm, &args, dir, entry, mode);
+       return create_new_nondir(idmap, fm, &args, dir, entry, mode);
 }
 
 static int fuse_create(struct mnt_idmap *idmap, struct inode *dir,
@@ -917,7 +931,7 @@ static struct dentry *fuse_mkdir(struct mnt_idmap *idmap, struct inode *dir,
        args.in_args[0].value = &inarg;
        args.in_args[1].size = entry->d_name.len + 1;
        args.in_args[1].value = entry->d_name.name;
-       return ERR_PTR(create_new_entry(idmap, fm, &args, dir, entry, S_IFDIR));
+       return create_new_entry(idmap, fm, &args, dir, entry, S_IFDIR);
 }
 
 static int fuse_symlink(struct mnt_idmap *idmap, struct inode *dir,
@@ -934,7 +948,7 @@ static int fuse_symlink(struct mnt_idmap *idmap, struct inode *dir,
        args.in_args[1].value = entry->d_name.name;
        args.in_args[2].size = len;
        args.in_args[2].value = link;
-       return create_new_entry(idmap, fm, &args, dir, entry, S_IFLNK);
+       return create_new_nondir(idmap, fm, &args, dir, entry, S_IFLNK);
 }
 
 void fuse_flush_time_update(struct inode *inode)
@@ -1131,7 +1145,7 @@ static int fuse_link(struct dentry *entry, struct inode *newdir,
        args.in_args[0].value = &inarg;
        args.in_args[1].size = newent->d_name.len + 1;
        args.in_args[1].value = newent->d_name.name;
-       err = create_new_entry(&invalid_mnt_idmap, fm, &args, newdir, newent, inode->i_mode);
+       err = create_new_nondir(&invalid_mnt_idmap, fm, &args, newdir, newent, inode->i_mode);
        if (!err)
                fuse_update_ctime_in_cache(inode);
        else if (err == -EINTR)