Wrapfs: file operations

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>

diff --git a/fs/wrapfs/file.c b/fs/wrapfs/file.c
new file mode 100644 (file)
index 0000000..42142eb
--- /dev/null
+++ b/fs/wrapfs/file.c
@@ -0,0 +1,277 @@
+/*
+ * Copyright (c) 1998-2010 Erez Zadok
+ * Copyright (c) 2009     Shrikar Archak
+ * Copyright (c) 2003-2010 Stony Brook University
+ * Copyright (c) 2003-2010 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "wrapfs.h"
+
+static ssize_t wrapfs_read(struct file *file, char __user *buf,
+                          size_t count, loff_t *ppos)
+{
+       int err;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+
+       lower_file = wrapfs_lower_file(file);
+       err = vfs_read(lower_file, buf, count, ppos);
+       /* update our inode atime upon a successful lower read */
+       if (err >= 0)
+               fsstack_copy_attr_atime(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+
+       return err;
+}
+
+static ssize_t wrapfs_write(struct file *file, const char __user *buf,
+                           size_t count, loff_t *ppos)
+{
+       int err = 0;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+
+       lower_file = wrapfs_lower_file(file);
+       err = vfs_write(lower_file, buf, count, ppos);
+       /* update our inode times+sizes upon a successful lower write */
+       if (err >= 0) {
+               fsstack_copy_inode_size(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               fsstack_copy_attr_times(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+       }
+
+       return err;
+}
+
+static int wrapfs_readdir(struct file *file, void *dirent, filldir_t filldir)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+       struct dentry *dentry = file->f_path.dentry;
+
+       lower_file = wrapfs_lower_file(file);
+       err = vfs_readdir(lower_file, filldir, dirent);
+       file->f_pos = lower_file->f_pos;
+       if (err >= 0)           /* copy the atime */
+               fsstack_copy_attr_atime(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+       return err;
+}
+
+static long wrapfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err = -ENOTTY;
+       struct file *lower_file;
+
+       lower_file = wrapfs_lower_file(file);
+
+       /* XXX: use vfs_ioctl if/when VFS exports it */
+       if (!lower_file || !lower_file->f_op)
+               goto out;
+       if (lower_file->f_op->unlocked_ioctl) {
+               err = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
+       } else if (lower_file->f_op->ioctl) {
+               lock_kernel();
+               err = lower_file->f_op->ioctl(
+                       lower_file->f_path.dentry->d_inode,
+                       lower_file, cmd, arg);
+               unlock_kernel();
+       }
+
+out:
+       return err;
+}
+
+static int wrapfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       int err = 0;
+       bool willwrite;
+       struct file *lower_file;
+       const struct vm_operations_struct *saved_vm_ops = NULL;
+
+       /* this might be deferred to mmap's writepage */
+       willwrite = ((vma->vm_flags | VM_SHARED | VM_WRITE) == vma->vm_flags);
+
+       /*
+        * File systems which do not implement ->writepage may use
+        * generic_file_readonly_mmap as their ->mmap op.  If you call
+        * generic_file_readonly_mmap with VM_WRITE, you'd get an -EINVAL.
+        * But we cannot call the lower ->mmap op, so we can't tell that
+        * writeable mappings won't work.  Therefore, our only choice is to
+        * check if the lower file system supports the ->writepage, and if
+        * not, return EINVAL (the same error that
+        * generic_file_readonly_mmap returns in that case).
+        */
+       lower_file = wrapfs_lower_file(file);
+       if (willwrite && !lower_file->f_mapping->a_ops->writepage) {
+               err = -EINVAL;
+               printk(KERN_ERR "wrapfs: lower file system does not "
+                      "support writeable mmap\n");
+               goto out;
+       }
+
+       /*
+        * find and save lower vm_ops.
+        *
+        * XXX: the VFS should have a cleaner way of finding the lower vm_ops
+        */
+       if (!WRAPFS_F(file)->lower_vm_ops) {
+               err = lower_file->f_op->mmap(lower_file, vma);
+               if (err) {
+                       printk(KERN_ERR "wrapfs: lower mmap failed %d\n", err);
+                       goto out;
+               }
+               saved_vm_ops = vma->vm_ops; /* save: came from lower ->mmap */
+               err = do_munmap(current->mm, vma->vm_start,
+                               vma->vm_end - vma->vm_start);
+               if (err) {
+                       printk(KERN_ERR "wrapfs: do_munmap failed %d\n", err);
+                       goto out;
+               }
+       }
+
+       /*
+        * Next 3 lines are all I need from generic_file_mmap.  I definitely
+        * don't want its test for ->readpage which returns -ENOEXEC.
+        */
+       file_accessed(file);
+       vma->vm_ops = &wrapfs_vm_ops;
+       vma->vm_flags |= VM_CAN_NONLINEAR;
+
+       file->f_mapping->a_ops = &wrapfs_aops; /* set our aops */
+       if (!WRAPFS_F(file)->lower_vm_ops) /* save for our ->fault */
+               WRAPFS_F(file)->lower_vm_ops = saved_vm_ops;
+
+out:
+       return err;
+}
+
+static int wrapfs_open(struct inode *inode, struct file *file)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+       struct path lower_path;
+
+       /* don't open unhashed/deleted files */
+       if (d_unhashed(file->f_path.dentry)) {
+               err = -ENOENT;
+               goto out_err;
+       }
+
+       file->private_data =
+               kzalloc(sizeof(struct wrapfs_file_info), GFP_KERNEL);
+       if (!WRAPFS_F(file)) {
+               err = -ENOMEM;
+               goto out_err;
+       }
+
+       /* open lower object and link wrapfs's file struct to lower's */
+       wrapfs_get_lower_path(file->f_path.dentry, &lower_path);
+       path_get(&lower_path);
+       lower_file = dentry_open(lower_path.dentry, lower_path.mnt,
+                                file->f_flags, current_cred());
+       if (IS_ERR(lower_file)) {
+               err = PTR_ERR(lower_file);
+               lower_file = wrapfs_lower_file(file);
+               if (lower_file) {
+                       wrapfs_set_lower_file(file, NULL);
+                       fput(lower_file); /* fput calls dput for lower_dentry */
+               }
+       } else {
+               wrapfs_set_lower_file(file, lower_file);
+       }
+
+       if (err)
+               kfree(WRAPFS_F(file));
+       else
+               fsstack_copy_attr_all(inode, wrapfs_lower_inode(inode));
+       wrapfs_put_lower_path(file->f_path.dentry, &lower_path);
+out_err:
+       return err;
+}
+
+static int wrapfs_flush(struct file *file, fl_owner_t id)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+
+       lower_file = wrapfs_lower_file(file);
+       if (lower_file && lower_file->f_op && lower_file->f_op->flush)
+               err = lower_file->f_op->flush(lower_file, id);
+
+       return err;
+}
+
+/* release all lower object references & free the file info structure */
+static int wrapfs_file_release(struct inode *inode, struct file *file)
+{
+       struct file *lower_file;
+
+       lower_file = wrapfs_lower_file(file);
+       if (lower_file) {
+               wrapfs_set_lower_file(file, NULL);
+               fput(lower_file);
+       }
+
+       kfree(WRAPFS_F(file));
+       return 0;
+}
+
+static int wrapfs_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+       int err;
+       struct file *lower_file;
+       struct path lower_path;
+
+       lower_file = wrapfs_lower_file(file);
+       wrapfs_get_lower_path(dentry, &lower_path);
+       err = vfs_fsync(lower_file, lower_path.dentry, datasync);
+       wrapfs_put_lower_path(dentry, &lower_path);
+
+       return err;
+}
+
+static int wrapfs_fasync(int fd, struct file *file, int flag)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+
+       lock_kernel();
+       lower_file = wrapfs_lower_file(file);
+       if (lower_file->f_op && lower_file->f_op->fasync)
+               err = lower_file->f_op->fasync(fd, lower_file, flag);
+       unlock_kernel();
+
+       return err;
+}
+
+const struct file_operations wrapfs_main_fops = {
+       .llseek         = generic_file_llseek,
+       .read           = wrapfs_read,
+       .write          = wrapfs_write,
+       .unlocked_ioctl = wrapfs_ioctl,
+       .mmap           = wrapfs_mmap,
+       .open           = wrapfs_open,
+       .flush          = wrapfs_flush,
+       .release        = wrapfs_file_release,
+       .fsync          = wrapfs_fsync,
+       .fasync         = wrapfs_fasync,
+};
+
+/* trimmed directory options */
+const struct file_operations wrapfs_dir_fops = {
+       .llseek         = generic_file_llseek,
+       .read           = generic_read_dir,
+       .readdir        = wrapfs_readdir,
+       .unlocked_ioctl = wrapfs_ioctl,
+       .open           = wrapfs_open,
+       .release        = wrapfs_file_release,
+       .flush          = wrapfs_flush,
+       .fsync          = wrapfs_fsync,
+       .fasync         = wrapfs_fasync,
+};