linux 6.7 compat: handle superblock shrinker member change

In 6.7 the superblock shrinker member s_shrink has changed from being an embedded struct to a pointer. Detect this, and don't take a reference if it already is one. Signed-off-by: Rob Norris <[email protected]> Sponsored-by: https://github.com/sponsors/robn
openzfs · Dec 21, 2023 · 18a9185 · 18a9185
1 parent 3c13601
commit 18a9185
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Showing 2 changed files with 42 additions and 3 deletions.
diff --git a/config/kernel-shrink.m4 b/config/kernel-shrink.m4
@@ -19,12 +19,44 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_SUPER_BLOCK_S_SHRINK], [
 	],[])
 ])
 
+dnl #
+dnl # 6.7 API change
+dnl # s_shrink is now a pointer.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_SUPER_BLOCK_S_SHRINK_PTR], [
+	ZFS_LINUX_TEST_SRC([super_block_s_shrink_ptr], [
+		#include <linux/fs.h>
+		unsigned long shrinker_cb(struct shrinker *shrink,
+		    struct shrink_control *sc) { return 0; }
+		static struct shrinker shrinker = {
+			.count_objects = shrinker_cb,
+			.scan_objects = shrinker_cb,
+			.seeks = DEFAULT_SEEKS,
+		};
+		static const struct super_block
+		    sb __attribute__ ((unused)) = {
+			.s_shrink = &shrinker,
+		};
+	],[])
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_SUPER_BLOCK_S_SHRINK], [
 	AC_MSG_CHECKING([whether super_block has s_shrink])
 	ZFS_LINUX_TEST_RESULT([super_block_s_shrink], [
 		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_SUPER_BLOCK_S_SHRINK, 1,
+			[have super_block s_shrink])
 	],[
-		ZFS_LINUX_TEST_ERROR([sb->s_shrink()])
+		AC_MSG_RESULT(no)
+		AC_MSG_CHECKING([whether super_block has s_shrink pointer])
+		ZFS_LINUX_TEST_RESULT([super_block_s_shrink_ptr], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE(HAVE_SUPER_BLOCK_S_SHRINK_PTR, 1,
+				[have super_block s_shrink pointer])
+		],[
+			AC_MSG_RESULT(no)
+			ZFS_LINUX_TEST_ERROR([sb->s_shrink()])
+		])
 	])
 ])
 
@@ -174,6 +206,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SHRINK_CONTROL_STRUCT], [
 
 AC_DEFUN([ZFS_AC_KERNEL_SRC_SHRINKER], [
 	ZFS_AC_KERNEL_SRC_SUPER_BLOCK_S_SHRINK
+	ZFS_AC_KERNEL_SRC_SUPER_BLOCK_S_SHRINK_PTR
 	ZFS_AC_KERNEL_SRC_SHRINK_CONTROL_HAS_NID
 	ZFS_AC_KERNEL_SRC_SHRINKER_CALLBACK
 	ZFS_AC_KERNEL_SRC_SHRINK_CONTROL_STRUCT

diff --git a/module/os/linux/zfs/zfs_vfsops.c b/module/os/linux/zfs/zfs_vfsops.c
@@ -1240,12 +1240,18 @@ zfs_prune_aliases(zfsvfs_t *zfsvfs, unsigned long nr_to_scan)
  * and inode caches.  This can occur when the ARC needs to free meta data
  * blocks but can't because they are all pinned by entries in these caches.
  */
+#if defined(HAVE_SUPER_BLOCK_S_SHRINK)
+#define	S_SHRINK(sb)	(&(sb)->s_shrink)
+#elif defined(HAVE_SUPER_BLOCK_S_SHRINK_PTR)
+#define	S_SHRINK(sb)	((sb)->s_shrink)
+#endif
+
 int
 zfs_prune(struct super_block *sb, unsigned long nr_to_scan, int *objects)
 {
 	zfsvfs_t *zfsvfs = sb->s_fs_info;
 	int error = 0;
-	struct shrinker *shrinker = &sb->s_shrink;
+	struct shrinker *shrinker = S_SHRINK(sb);
 	struct shrink_control sc = {
 		.nr_to_scan = nr_to_scan,
 		.gfp_mask = GFP_KERNEL,
@@ -1257,7 +1263,7 @@ zfs_prune(struct super_block *sb, unsigned long nr_to_scan, int *objects)
 #if defined(HAVE_SPLIT_SHRINKER_CALLBACK) && \
 	defined(SHRINK_CONTROL_HAS_NID) && \
 	defined(SHRINKER_NUMA_AWARE)
-	if (sb->s_shrink.flags & SHRINKER_NUMA_AWARE) {
+	if (shrinker->flags & SHRINKER_NUMA_AWARE) {
 		*objects = 0;
 		for_each_online_node(sc.nid) {
 			*objects += (*shrinker->scan_objects)(shrinker, &sc);