compat_generic_segment_checks.c

ocfs1.4.1 oracle分布式文件系统

/*
 * compat_generic_segment_checks.c
 *
 * This code has been copied from mainline linux kernel git commit
 * e7b34019606ab1dd06196635e931b0c302799228 to allow ocfs2 to build
 * against older kernels. For license, refer to mm/filemap.c in mainline
 * linux kernel.
 *
 */

#include <linux/fs.h>
#ifndef NO_LINUX_UACCESS_H
#include <linux/uaccess.h>
#else
#include <asm/uaccess.h>
#endif
#include <linux/uio.h>

/*
 * Performs necessary checks before doing a write
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
 * @count:	number of bytes to write
 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
 *
 * Adjust number of segments and amount of bytes to write (nr_segs should be
 * properly initialized first). Returns appropriate error code that caller
 * should return or zero in case that write should be allowed.
 */
int generic_segment_checks(const struct iovec *iov, unsigned long *nr_segs,
			   size_t *count, int access_flags)
{
	unsigned long   seg;
	size_t cnt = 0;
	for (seg = 0; seg < *nr_segs; seg++) {
		const struct iovec *iv = &iov[seg];

		/*
		 * If any segment has a negative length, or the cumulative
		 * length ever wraps negative then return -EINVAL.
		 */
		cnt += iv->iov_len;
		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		*nr_segs = seg;
		cnt -= iv->iov_len;	/* This segment is no good */
		break;
	}
	*count = cnt;
	return 0;
}