freebsd-dev/config/kernel-vfs-set_page_dirty.m4
Coleman Kane 1c24bf966c
Linux 5.14 compat: explicity assign set_page_dirty
Kernel 5.14 introduced a change where set_page_dirty of
struct address_space_operations is no longer implicitly set to
__set_page_dirty_buffers(), which ended up resulting in a NULL
pointer deref in the kernel when it is attempted to be called.
This change sets .set_page_dirty in the structure to
__set_page_dirty_nobuffers(), which was introduced with the
related patch set. The breaking change was introduce in commit
0af573780b0b13fceb7fabd49dc1b073cee9a507 to torvalds/linux.git.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #12427
2021-07-26 10:55:55 -07:00

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dnl #
dnl # Linux 5.14 adds a change to require set_page_dirty to be manually
dnl # wired up in struct address_space_operations. Determine if this needs
dnl # to be done. This patch set also introduced __set_page_dirty_nobuffers
dnl # declaration in linux/pagemap.h, so these tests look for the presence
dnl # of that function to tell the compiler to assign set_page_dirty in
dnl # module/os/linux/zfs/zpl_file.c
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_VFS_SET_PAGE_DIRTY_NOBUFFERS], [
ZFS_LINUX_TEST_SRC([vfs_has_set_page_dirty_nobuffers], [
#include <linux/pagemap.h>
#include <linux/fs.h>
static const struct address_space_operations
aops __attribute__ ((unused)) = {
.set_page_dirty = __set_page_dirty_nobuffers,
};
],[])
])
AC_DEFUN([ZFS_AC_KERNEL_VFS_SET_PAGE_DIRTY_NOBUFFERS], [
dnl #
dnl # Linux 5.14 change requires set_page_dirty() to be assigned
dnl # in address_space_operations()
dnl #
AC_MSG_CHECKING([__set_page_dirty_nobuffers exists])
ZFS_LINUX_TEST_RESULT([vfs_has_set_page_dirty_nobuffers], [
AC_MSG_RESULT([yes])
AC_DEFINE(HAVE_VFS_SET_PAGE_DIRTY_NOBUFFERS, 1,
[__set_page_dirty_nobuffers exists])
],[
AC_MSG_RESULT([no])
])
])