Linux: Fix builds on RHEL4

RHEL4 has a very old 2.6 kernel (2.6.9), which predates the start of
the Linux git tree. When I started using page_offset, I mistakenly assumed
that everything in the initial commit to that tree was available in all
2.6 versions we care about. That isn't the case, sadly.

Secondly, the new readpage code uses zero_user_segments, which has only
been available in the mainline kernel since 2.6.25 (RHEL5 appears to have
a backport)

Implement local wrappers for both of these functions when configure can't
find them in the kernel we're building for.

These functions have been created independently of the Linux tree.
page_offset is a copy of the code we used before we replaced it.
zero_user_segments() is a first-principles implementation
of the function (which zeros a pair of memory ranges within a single page)

FIXES 126678

Change-Id: I622aec4d653567d5234e7a127b981e97468bbe7c
Reviewed-on: http://gerrit.openafs.org/1525
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>

diff --git a/acinclude.m4 b/acinclude.m4
index c083e27c96f6bc19a4b92cf78cbbec78e3ad43c1..2b37105a22c91b1b30776c998c43bc2eb6e73059 100644 (file)
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -812,6 +812,8 @@ case $AFS_SYSNAME in *_linux* | *_umlinux*)
                  LINUX_HAVE_GRAB_CACHE_PAGE_WRITE_BEGIN
                 LINUX_HAVE_PAGEVEC_LRU_ADD_FILE
                 LINUX_HAVE_SPLICE_DIRECT_TO_ACTOR
+                LINUX_HAVE_PAGE_OFFSET
+                LINUX_HAVE_ZERO_USER_SEGMENTS
                  LINUX_STRUCT_TASK_HAS_CRED
                 LINUX_STRUCT_PROC_DIR_ENTRY_HAS_OWNER
                 LINUX_HAVE_KMEM_CACHE_T

diff --git a/src/afs/LINUX/osi_compat.h b/src/afs/LINUX/osi_compat.h
index 5e5205695fb2c6f2d8e54ec4e95e62354c011b9e..0b52019cf76147c22d6087f9a904ed5b9506b623 100644 (file)
--- a/src/afs/LINUX/osi_compat.h
+++ b/src/afs/LINUX/osi_compat.h
@@ -203,3 +203,30 @@ afs_linux_cred_is_current(afs_ucred_t *cred)
 # endif
 #endif
 #endif
+
+#ifndef HAVE_PAGE_OFFSET
+static inline loff_t
+page_offset(struct page *pp)
+{
+    return (((loff_t) pp->index) << PAGE_CACHE_SHIFT);
+}
+#endif
+
+#ifndef HAVE_ZERO_USER_SEGMENTS
+static inline void
+zero_user_segments(struct page *pp, unsigned int from1, unsigned int to1,
+                  unsigned int from2, unsigned int to2)
+{
+    void *base = kmap_atomic(pp, KM_USER0);
+
+    if (to1 > from1)
+       memset(base + from1, 0, to1 - from1);
+
+    if (to2 > from2)
+       memset(base + from2, 0, to2 - from2);
+
+    flush_dcache_page(pp);
+    kunmap_atomic(base, KM_USER0);
+}
+#endif
+

diff --git a/src/cf/linux-test4.m4 b/src/cf/linux-test4.m4
index 2420b7b2a7c4be6c738a8b0b4e2c3f46a73308f2..14cf9a6beb25d6c08313a2f169dcfff3870a9b99 100644 (file)
--- a/src/cf/linux-test4.m4
+++ b/src/cf/linux-test4.m4
@@ -1231,3 +1231,29 @@ _bdi.name = NULL;],
     AC_DEFINE([STRUCT_BDI_HAS_NAME], 1, [define if struct backing_dev_info has a name member])
   fi])
 
+AC_DEFUN([LINUX_HAVE_ZERO_USER_SEGMENTS], [
+  AC_MSG_CHECKING([for zero_user_segments])
+  AC_CACHE_VAL([ac_cv_linux_have_zero_user_segments], [
+    AC_TRY_KBUILD(
+[#include <linux/highmem.h>],
+[zero_user_segments(NULL, 0, 0, 0, 0);],
+      ac_cv_linux_have_zero_user_segments=yes,
+      ac_cv_linux_have_zero_user_segments=no)])
+  AC_MSG_RESULT($ac_cv_linux_have_zero_user_segments)
+  if test "x$ac_cv_linux_have_zero_user_segments" = "xyes"; then
+    AC_DEFINE([HAVE_ZERO_USER_SEGMENTS], 1, [define if your kernel has the zero_user_segments function])
+  fi])
+
+AC_DEFUN([LINUX_HAVE_PAGE_OFFSET], [
+  AC_MSG_CHECKING([for page_offset])
+  AC_CACHE_VAL([ac_cv_linux_have_page_offset], [
+    AC_TRY_KBUILD(
+[#include <linux/pagemap.h>],
+[page_offset(NULL);],
+      ac_cv_linux_have_page_offset=yes,
+      ac_cv_linux_have_page_offset=no)])
+  AC_MSG_RESULT($ac_cv_linux_have_page_offset)
+  if test "x$ac_cv_linux_have_page_offset" = "xyes"; then
+    AC_DEFINE([HAVE_PAGE_OFFSET], 1, [define if your kernel has the page_offset function])
+  fi])
+