mirror_zfs/config/kernel-vfs-rw-iterate.m4
Chunwei Chen 7a789346af Fix loop device becomes read-only
Commit 933ec99 removes read and write from f_op because the vfs layer will
select iter_write or aio_write automatically. However, for Linux <= 4.0,
loop_set_fd will actually check f_op->write and set read-only if not exists.
This patch add them back and use the generic do_sync_{read,write} for
aio_{read,write} and new_sync_{read,write} for {read,write}_iter.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes #5776 
Closes #5855
2017-03-06 09:20:20 -08:00

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dnl #
dnl # Linux 3.16 API
dnl #
AC_DEFUN([ZFS_AC_KERNEL_VFS_RW_ITERATE],
[AC_MSG_CHECKING([whether fops->read/write_iter() are available])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
ssize_t test_read(struct kiocb *kiocb, struct iov_iter *to)
{ return 0; }
ssize_t test_write(struct kiocb *kiocb, struct iov_iter *from)
{ return 0; }
static const struct file_operations
fops __attribute__ ((unused)) = {
.read_iter = test_read,
.write_iter = test_write,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_VFS_RW_ITERATE, 1,
[fops->read/write_iter() are available])
ZFS_AC_KERNEL_NEW_SYNC_READ
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # Linux 4.1 API
dnl #
AC_DEFUN([ZFS_AC_KERNEL_NEW_SYNC_READ],
[AC_MSG_CHECKING([whether new_sync_read() is available])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
new_sync_read(NULL, NULL, 0, NULL);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_NEW_SYNC_READ, 1,
[new_sync_read() is available])
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # Linux 4.1.x API
dnl #
AC_DEFUN([ZFS_AC_KERNEL_GENERIC_WRITE_CHECKS],
[AC_MSG_CHECKING([whether generic_write_checks() takes kiocb])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
struct kiocb *iocb = NULL;
struct iov_iter *iov = NULL;
generic_write_checks(iocb, iov);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_GENERIC_WRITE_CHECKS_KIOCB, 1,
[generic_write_checks() takes kiocb])
],[
AC_MSG_RESULT(no)
])
])