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Diffstat (limited to 'fs/sdcardfs/mmap.c')
-rw-r--r-- | fs/sdcardfs/mmap.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/fs/sdcardfs/mmap.c b/fs/sdcardfs/mmap.c new file mode 100644 index 000000000000..e21f64675a80 --- /dev/null +++ b/fs/sdcardfs/mmap.c @@ -0,0 +1,81 @@ +/* + * fs/sdcardfs/mmap.c + * + * Copyright (c) 2013 Samsung Electronics Co. Ltd + * Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun, + * Sunghwan Yun, Sungjong Seo + * + * This program has been developed as a stackable file system based on + * the WrapFS which written by + * + * Copyright (c) 1998-2011 Erez Zadok + * Copyright (c) 2009 Shrikar Archak + * Copyright (c) 2003-2011 Stony Brook University + * Copyright (c) 2003-2011 The Research Foundation of SUNY + * + * This file is dual licensed. It may be redistributed and/or modified + * under the terms of the Apache 2.0 License OR version 2 of the GNU + * General Public License. + */ + +#include "sdcardfs.h" + +static int sdcardfs_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + int err; + struct file *file, *lower_file; + const struct vm_operations_struct *lower_vm_ops; + struct vm_area_struct lower_vma; + + memcpy(&lower_vma, vma, sizeof(struct vm_area_struct)); + file = lower_vma.vm_file; + lower_vm_ops = SDCARDFS_F(file)->lower_vm_ops; + BUG_ON(!lower_vm_ops); + + lower_file = sdcardfs_lower_file(file); + /* + * XXX: vm_ops->fault may be called in parallel. Because we have to + * resort to temporarily changing the vma->vm_file to point to the + * lower file, a concurrent invocation of sdcardfs_fault could see a + * different value. In this workaround, we keep a different copy of + * the vma structure in our stack, so we never expose a different + * value of the vma->vm_file called to us, even temporarily. A + * better fix would be to change the calling semantics of ->fault to + * take an explicit file pointer. + */ + lower_vma.vm_file = lower_file; + err = lower_vm_ops->fault(&lower_vma, vmf); + return err; +} + +static ssize_t sdcardfs_direct_IO(struct kiocb *iocb, + struct iov_iter *iter, loff_t pos) +{ + /* + * This function returns zero on purpose in order to support direct IO. + * __dentry_open checks a_ops->direct_IO and returns EINVAL if it is null. + * + * However, this function won't be called by certain file operations + * including generic fs functions. * reads and writes are delivered to + * the lower file systems and the direct IOs will be handled by them. + * + * NOTE: exceptionally, on the recent kernels (since Linux 3.8.x), + * swap_writepage invokes this function directly. + */ + printk(KERN_INFO "%s, operation is not supported\n", __func__); + return 0; +} + +/* + * XXX: the default address_space_ops for sdcardfs is empty. We cannot set + * our inode->i_mapping->a_ops to NULL because too many code paths expect + * the a_ops vector to be non-NULL. + */ +const struct address_space_operations sdcardfs_aops = { + /* empty on purpose */ + .direct_IO = sdcardfs_direct_IO, +}; + +const struct vm_operations_struct sdcardfs_vm_ops = { + .fault = sdcardfs_fault, +}; |