From 6d68eea26da6afdefa41f6e14dadfc3a4231638f Mon Sep 17 00:00:00 2001 From: Erez Zadok Date: Mon, 4 Jan 2010 20:45:06 -0500 Subject: [PATCH] Wrapfs: file operations Signed-off-by: Erez Zadok --- fs/wrapfs/file.c | 277 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 277 insertions(+) create mode 100644 fs/wrapfs/file.c diff --git a/fs/wrapfs/file.c b/fs/wrapfs/file.c new file mode 100644 index 000000000000..42142eb77a74 --- /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, +}; -- 2.43.0