diff --git a/fs/devfs.c b/fs/devfs.c
index a7400df..d088c1a 100644
--- a/fs/devfs.c
+++ b/fs/devfs.c
@@ -78,13 +78,10 @@
 	if (cdev->flags & DEVFS_PARTITION_READONLY)
 		return -EPERM;
 
-	if (!cdev->ops->erase)
-		return -ENOSYS;
-
 	if (count + offset > cdev->size)
 		count = cdev->size - offset;
 
-	return cdev->ops->erase(cdev, count, offset + cdev->offset);
+	return cdev_erase(cdev, count, offset);
 }
 
 static int devfs_protect(struct device_d *_dev, FILE *f, size_t count, loff_t offset, int prot)
@@ -155,10 +152,7 @@
 {
 	struct cdev *cdev = f->priv;
 
-	if (cdev->ops->flush)
-		return cdev->ops->flush(cdev);
-
-	return 0;
+	return cdev_flush(cdev);
 }
 
 static int devfs_ioctl(struct device_d *_dev, FILE *f, int request, void *buf)
diff --git a/fs/fs.c b/fs/fs.c
index 1f6b3d3..c6cb499 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -171,14 +171,14 @@
 	dput(f->dentry);
 }
 
-static int check_fd(int fd)
+static FILE *fd_to_file(int fd)
 {
 	if (fd < 0 || fd >= MAX_FILES || !files[fd].in_use) {
 		errno = EBADF;
-		return -errno;
+		return ERR_PTR(-errno);
 	}
 
-	return 0;
+	return &files[fd];
 }
 
 static int create(struct dentry *dir, struct dentry *dentry)
@@ -205,14 +205,12 @@
 int ftruncate(int fd, loff_t length)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	if (f->size == FILE_SIZE_STREAM)
 		return 0;
 
@@ -232,14 +230,12 @@
 int ioctl(int fd, int request, void *buf)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	fsdrv = f->fsdev->driver;
 
 	if (fsdrv->ioctl)
@@ -279,14 +275,12 @@
 ssize_t pread(int fd, void *buf, size_t count, loff_t offset)
 {
 	loff_t pos;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	pos = f->pos;
 	f->pos = offset;
 	ret = __read(f, buf, count);
@@ -298,14 +292,12 @@
 
 ssize_t read(int fd, void *buf, size_t count)
 {
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	ret = __read(f, buf, count);
 
 	if (ret > 0)
@@ -348,14 +340,12 @@
 ssize_t pwrite(int fd, const void *buf, size_t count, loff_t offset)
 {
 	loff_t pos;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	pos = f->pos;
 	f->pos = offset;
 	ret = __write(f, buf, count);
@@ -367,14 +357,12 @@
 
 ssize_t write(int fd, const void *buf, size_t count)
 {
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	ret = __write(f, buf, count);
 
 	if (ret > 0)
@@ -386,14 +374,12 @@
 int flush(int fd)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	fsdrv = f->fsdev->driver;
 	if (fsdrv->flush)
 		ret = fsdrv->flush(&f->fsdev->dev, f);
@@ -406,17 +392,16 @@
 	return ret;
 }
 
-loff_t lseek(int fildes, loff_t offset, int whence)
+loff_t lseek(int fd, loff_t offset, int whence)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	loff_t pos;
 	int ret;
 
-	if (check_fd(fildes))
+	if (IS_ERR(f))
 		return -1;
 
-	f = &files[fildes];
 	fsdrv = f->fsdev->driver;
 
 	ret = -EINVAL;
@@ -461,12 +446,11 @@
 int erase(int fd, loff_t count, loff_t offset)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
-	f = &files[fd];
 	if (offset >= f->size)
 		return 0;
 	if (count == ERASE_SIZE_ALL || count > f->size - offset)
@@ -490,12 +474,11 @@
 int protect(int fd, size_t count, loff_t offset, int prot)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
-	f = &files[fd];
 	if (offset >= f->size)
 		return 0;
 	if (count > f->size - offset)
@@ -532,15 +515,13 @@
 void *memmap(int fd, int flags)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	void *retp = MAP_FAILED;
 	int ret;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return retp;
 
-	f = &files[fd];
-
 	fsdrv = f->fsdev->driver;
 
 	if (fsdrv->memmap)
@@ -558,14 +539,12 @@
 int close(int fd)
 {
 	struct fs_driver_d *fsdrv;
-	FILE *f;
+	FILE *f = fd_to_file(fd);
 	int ret = 0;
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
 	fsdrv = f->fsdev->driver;
 
 	if (fsdrv->close)
@@ -809,9 +788,6 @@
 	struct readdir_entry *entry;
 
 	entry = xzalloc(sizeof(*entry));
-	if (!entry)
-		return -ENOMEM;
-
 	memcpy(entry->d.d_name, name, namlen);
 	list_add_tail(&entry->list, &rd->dir->entries);
 
@@ -850,16 +826,11 @@
 
 int fstat(int fd, struct stat *s)
 {
-	FILE *f;
-	struct fs_device_d *fsdev;
+	FILE *f = fd_to_file(fd);
 
-	if (check_fd(fd))
+	if (IS_ERR(f))
 		return -errno;
 
-	f = &files[fd];
-
-	fsdev = f->fsdev;
-
 	stat_inode(f->f_inode, s);
 
 	return 0;
diff --git a/fs/ramfs.c b/fs/ramfs.c
index 4fba40d..3046afe 100644
--- a/fs/ramfs.c
+++ b/fs/ramfs.c
@@ -403,8 +403,6 @@
 	struct ramfs_inode *node;
 
 	node = xzalloc(sizeof(*node));
-	if (!node)
-		return NULL;
 
 	return &node->inode;
 }