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    bitmap.c bitmap.h dir.c file.c inode.c itree.c namei.c xiafs.h

  • file.c

  • ¶ 
    /*
 * Porting work to modern kernels copyright (C) Jeremy Bingham, 2013.
 * Based on work by Linus Torvalds, Q. Frank Xia, and others as noted.
 *
 * This port of Q. Frank Xia's xiafs was done using the existing minix
 * filesystem code, but based on the original xiafs code in pre-2.1.21 or so
 * kernels.
 */

/*
 *  linux/fs/xiafs/file.c
 *
 *  Copyright (C) 1991, 1992 Linus Torvalds
 *
 *  xiafs regular file handling primitives
 */

#include "xiafs.h"
#include <linux/pagemap.h>

/*
 * We have mostly NULLs here: the current defaults are OK for
 * the xiafs filesystem.
 */
  • ¶

    While it was once not the case, all of the file operations for xiafs are handled by default functions. Even in earlier versions, however, many of the function pointers in xiafs_file_operations were filled by the defaults. 

    const struct file_operations xiafs_file_operations = {
	.llseek		= generic_file_llseek,
	.read		= do_sync_read,
	.aio_read	= generic_file_aio_read,
	.write		= do_sync_write,
	.aio_write	= generic_file_aio_write,
	.mmap		= generic_file_mmap,
	.fsync		= generic_file_fsync,
	.splice_read	= generic_file_splice_read,
};

/* a new setattr function is in the minix source tree. Trying to bring that in
 * and see how it works. */
  • ¶

    Sets attributes on the inode. Despite the name, it is not related to the file attributes listed with lsattr and changed with chattr. This handles changing the inode's mode, owner, group, timestamps, and size. See include/linux/fs.h for more on this.

    static int xiafs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = dentry->d_inode;
        int error;
  • ¶

    Check that changing the attributes is OK and won't blow up.

            error = inode_change_ok(inode, attr);
        if (error)
                return error;
  • ¶

    If the file size is to be changed, do so. Check that the size can be changed, then truncate the file to that size.

            if ((attr->ia_valid & ATTR_SIZE) &&
            attr->ia_size != i_size_read(inode)) {
                error = inode_newsize_ok(inode, attr->ia_size);
                if (error)
                        return error;
		truncate_setsize(inode, attr->ia_size);
		xiafs_truncate(inode);
        }
  • ¶

    Copy the new attributes to the inode and mark the inode as dirty so it gets written out eventually.

            setattr_copy(inode, attr);
        mark_inode_dirty(inode);
        return 0;
}
  • ¶

    Define the setattr and getattr inode operation functions pointers for the xiafs_file_inode_operations struct.

    const struct inode_operations xiafs_file_inode_operations = {
	.setattr 	= xiafs_setattr,
  • ¶

    xiafs_getattr lives in inode.c.

    	.getattr	= xiafs_getattr,
};