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Adding ZERO_PAGE detection

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On some architectures ZERO_PAGE is unavailable because it references
a GPL exported symbol of empty_zero_page. Originally e08b993 removed
the call to PAGE_ZERO(0) for assignment to the abd_zero_page. However,
a simple check can be done to avoid a kernel allocation and free for
the abd_zero_page if ZERO_PAGE is available.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #13199
This commit is contained in:
Brian Atkinson
2022-03-14 13:37:39 -06:00
committed by GitHub
parent dad2b19fff
commit becc717f61
3 changed files with 41 additions and 3 deletions
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config/kernel-zero_page.m4
+27
View File
@@ -0,0 +1,27 @@
dnl #
dnl # ZERO_PAGE() is an alias for emtpy_zero_page. On certain architectures
dnl # this is a GPL exported variable.
dnl #
dnl #
dnl # Checking if ZERO_PAGE is exported GPL-only
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_ZERO_PAGE], [
ZFS_LINUX_TEST_SRC([zero_page], [
#include <asm/pgtable.h>
], [
struct page *p __attribute__ ((unused));
p = ZERO_PAGE(0);
], [], [ZFS_META_LICENSE])
])
AC_DEFUN([ZFS_AC_KERNEL_ZERO_PAGE], [
AC_MSG_CHECKING([whether ZERO_PAGE() is GPL-only])
ZFS_LINUX_TEST_RESULT([zero_page_license], [
AC_MSG_RESULT(no)
], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_ZERO_PAGE_GPL_ONLY, 1,
[ZERO_PAGE() is GPL-only])
])
])
config/kernel.m4
+2
View File
@@ -137,6 +137,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
ZFS_AC_KERNEL_SRC_PAGEMAP_FOLIO_WAIT_BIT
ZFS_AC_KERNEL_SRC_ADD_DISK
ZFS_AC_KERNEL_SRC_KTHREAD
ZFS_AC_KERNEL_SRC_ZERO_PAGE
AC_MSG_CHECKING([for available kernel interfaces])
ZFS_LINUX_TEST_COMPILE_ALL([kabi])
@@ -247,6 +248,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
ZFS_AC_KERNEL_PAGEMAP_FOLIO_WAIT_BIT
ZFS_AC_KERNEL_ADD_DISK
ZFS_AC_KERNEL_KTHREAD
ZFS_AC_KERNEL_ZERO_PAGE
])
dnl #