82 lines
2.7 KiB
C
82 lines
2.7 KiB
C
/*
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* fs/sdcardfs/mmap.c
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*
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* Copyright (c) 2013 Samsung Electronics Co. Ltd
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* Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun,
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* Sunghwan Yun, Sungjong Seo
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*
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* This program has been developed as a stackable file system based on
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* the WrapFS which written by
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*
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* Copyright (c) 1998-2011 Erez Zadok
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* Copyright (c) 2009 Shrikar Archak
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* Copyright (c) 2003-2011 Stony Brook University
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* Copyright (c) 2003-2011 The Research Foundation of SUNY
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*
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* This file is dual licensed. It may be redistributed and/or modified
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* under the terms of the Apache 2.0 License OR version 2 of the GNU
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* General Public License.
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*/
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#include "sdcardfs.h"
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static int sdcardfs_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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int err;
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struct file *file, *lower_file;
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const struct vm_operations_struct *lower_vm_ops;
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struct vm_area_struct lower_vma;
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memcpy(&lower_vma, vma, sizeof(struct vm_area_struct));
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file = lower_vma.vm_file;
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lower_vm_ops = SDCARDFS_F(file)->lower_vm_ops;
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BUG_ON(!lower_vm_ops);
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lower_file = sdcardfs_lower_file(file);
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/*
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* XXX: vm_ops->fault may be called in parallel. Because we have to
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* resort to temporarily changing the vma->vm_file to point to the
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* lower file, a concurrent invocation of sdcardfs_fault could see a
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* different value. In this workaround, we keep a different copy of
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* the vma structure in our stack, so we never expose a different
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* value of the vma->vm_file called to us, even temporarily. A
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* better fix would be to change the calling semantics of ->fault to
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* take an explicit file pointer.
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*/
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lower_vma.vm_file = lower_file;
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err = lower_vm_ops->fault(&lower_vma, vmf);
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return err;
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}
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static ssize_t sdcardfs_direct_IO(struct kiocb *iocb,
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struct iov_iter *iter, loff_t offset)
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{
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/*
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* This function returns zero on purpose in order to support direct IO.
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* __dentry_open checks a_ops->direct_IO and returns EINVAL if it is null.
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*
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* However, this function won't be called by certain file operations
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* including generic fs functions. * reads and writes are delivered to
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* the lower file systems and the direct IOs will be handled by them.
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*
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* NOTE: exceptionally, on the recent kernels (since Linux 3.8.x),
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* swap_writepage invokes this function directly.
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*/
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printk(KERN_INFO "%s, operation is not supported\n", __func__);
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return 0;
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}
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/*
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* XXX: the default address_space_ops for sdcardfs is empty. We cannot set
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* our inode->i_mapping->a_ops to NULL because too many code paths expect
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* the a_ops vector to be non-NULL.
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*/
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const struct address_space_operations sdcardfs_aops = {
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/* empty on purpose */
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.direct_IO = sdcardfs_direct_IO,
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};
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const struct vm_operations_struct sdcardfs_vm_ops = {
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.fault = sdcardfs_fault,
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};
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