Linux 3.1 compat, super_block->s_shrink

The Linux 3.1 kernel has introduced the concept of per-filesystem
shrinkers which are directly assoicated with a super block.  Prior
to this change there was one shared global shrinker.

The zfs code relied on being able to call the global shrinker when
the arc_meta_limit was exceeded.  This would cause the VFS to drop
references on a fraction of the dentries in the dcache.  The ARC
could then safely reclaim the memory used by these entries and
honor the arc_meta_limit.  Unfortunately, when per-filesystem
shrinkers were added the old interfaces were made unavailable.

This change adds support to use the new per-filesystem shrinker
interface so we can continue to honor the arc_meta_limit.  The
major benefit of the new interface is that we can now target
only the zfs filesystem for dentry and inode pruning.  Thus we
can minimize any impact on the caching of other filesystems.

In the context of making this change several other important
issues related to managing the ARC were addressed, they include:

* The dnlc_reduce_cache() function which was called by the ARC
to drop dentries for the Posix layer was replaced with a generic
zfs_prune_t callback.  The ZPL layer now registers a callback to
drop these dentries removing a layering violation which dates
back to the Solaris code.  This callback can also be used by
other ARC consumers such as Lustre.

  arc_add_prune_callback()
  arc_remove_prune_callback()

* The arc_reduce_dnlc_percent module option has been changed to
arc_meta_prune for clarity.  The dnlc functions are specific to
Solaris's VFS and have already been largely eliminated already.
The replacement tunable now represents the number of bytes the
prune callback will request when invoked.

* Less aggressively invoke the prune callback.  We used to call
this whenever we exceeded the arc_meta_limit however that's not
strictly correct since it results in over zeleous reclaim of
dentries and inodes.  It is now only called once the arc_meta_limit
is exceeded and every effort has been made to evict other data from
the ARC cache.

* More promptly manage exceeding the arc_meta_limit.  When reading
meta data in to the cache if a buffer was unable to be recycled
notify the arc_reclaim thread to invoke the required prune.

* Added arcstat_prune kstat which is incremented when the ARC
is forced to request that a consumer prune its cache.  Remember
this will only occur when the ARC has no other choice.  If it
can evict buffers safely without invoking the prune callback
it will.

* This change is also expected to resolve the unexpect collapses
of the ARC cache.  This would occur because when exceeded just the
arc_meta_limit reclaim presure would be excerted on the arc_c
value via arc_shrink().  This effectively shrunk the entire cache
when really we just needed to reclaim meta data.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #466
Closes #292

65 files changed, 858 insertions, 51 deletions

diff --git a/Makefile.in b/Makefile.in
index 332efc173..37c813cd3 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -92,6 +92,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/Makefile.in b/cmd/Makefile.in
index ee3f4bef2..eb86e2796 100644
--- a/cmd/Makefile.in
+++ b/cmd/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/mount_zfs/Makefile.in b/cmd/mount_zfs/Makefile.in
index 73660d21b..44d07667e 100644
--- a/cmd/mount_zfs/Makefile.in
+++ b/cmd/mount_zfs/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/sas_switch_id/Makefile.in b/cmd/sas_switch_id/Makefile.in
index fb6ea65ec..889da1785 100644
--- a/cmd/sas_switch_id/Makefile.in
+++ b/cmd/sas_switch_id/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zdb/Makefile.in b/cmd/zdb/Makefile.in
index da3119592..4fd55e5fa 100644
--- a/cmd/zdb/Makefile.in
+++ b/cmd/zdb/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zfs/Makefile.in b/cmd/zfs/Makefile.in
index 55ca80892..0b9b4dcc6 100644
--- a/cmd/zfs/Makefile.in
+++ b/cmd/zfs/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zinject/Makefile.in b/cmd/zinject/Makefile.in
index 5e6f90ecb..8adfaab39 100644
--- a/cmd/zinject/Makefile.in
+++ b/cmd/zinject/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zpios/Makefile.in b/cmd/zpios/Makefile.in
index cf672f1e1..c0a84df6b 100644
--- a/cmd/zpios/Makefile.in
+++ b/cmd/zpios/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zpool/Makefile.in b/cmd/zpool/Makefile.in
index b915006f4..127b93690 100644
--- a/cmd/zpool/Makefile.in
+++ b/cmd/zpool/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zpool_id/Makefile.in b/cmd/zpool_id/Makefile.in
index aadd12413..29f83a3ff 100644
--- a/cmd/zpool_id/Makefile.in
+++ b/cmd/zpool_id/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zpool_layout/Makefile.in b/cmd/zpool_layout/Makefile.in
index e1b164313..514e88f5f 100644
--- a/cmd/zpool_layout/Makefile.in
+++ b/cmd/zpool_layout/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/ztest/Makefile.in b/cmd/ztest/Makefile.in
index e99cc9e85..dc6549b6c 100644
--- a/cmd/ztest/Makefile.in
+++ b/cmd/ztest/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/cmd/zvol_id/Makefile.in b/cmd/zvol_id/Makefile.in
index d6719fdb6..d657c8007 100644
--- a/cmd/zvol_id/Makefile.in
+++ b/cmd/zvol_id/Makefile.in
@@ -72,6 +72,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/config/kernel-shrink.m4 b/config/kernel-shrink.m4
new file mode 100644
index 000000000..ea748c974
--- /dev/null
+++ b/config/kernel-shrink.m4
@@ -0,0 +1,64 @@
+dnl #
+dnl # 3.1 API change
+dnl # The super_block structure now stores a per-filesystem shrinker.
+dnl # This interface is preferable because it can be used to specifically
+dnl # target only the zfs filesystem for pruning.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SHRINK], [
+	AC_MSG_CHECKING([whether super_block has s_shrink])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	],[
+		int (*shrink)(struct shrinker *, struct shrink_control *sc)
+			__attribute__ ((unused)) = NULL;
+		struct super_block sb __attribute__ ((unused)) = {
+			.s_shrink.shrink = shrink,
+			.s_shrink.seeks = DEFAULT_SEEKS,
+			.s_shrink.batch = 0,
+		};
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_SHRINK, 1, [struct super_block has s_shrink])
+
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_NR_CACHED_OBJECTS], [
+	AC_MSG_CHECKING([whether sops->nr_cached_objects() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	],[
+		int (*nr_cached_objects)(struct super_block *)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.nr_cached_objects = nr_cached_objects,
+		};
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_NR_CACHED_OBJECTS, 1,
+			[sops->nr_cached_objects() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_FREE_CACHED_OBJECTS], [
+	AC_MSG_CHECKING([whether sops->free_cached_objects() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	],[
+		void (*free_cached_objects)(struct super_block *, int)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.free_cached_objects = free_cached_objects,
+		};
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_FREE_CACHED_OBJECTS, 1,
+			[sops->free_cached_objects() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 63a3237ec..2afe77e63 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -34,12 +34,15 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_XATTR_HANDLER_SET
 	ZFS_AC_KERNEL_FSYNC
 	ZFS_AC_KERNEL_EVICT_INODE
+	ZFS_AC_KERNEL_NR_CACHED_OBJECTS
+	ZFS_AC_KERNEL_FREE_CACHED_OBJECTS
 	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_D_OBTAIN_ALIAS
 	ZFS_AC_KERNEL_CHECK_DISK_SIZE_CHANGE
 	ZFS_AC_KERNEL_TRUNCATE_SETSIZE
 	ZFS_AC_KERNEL_6ARGS_SECURITY_INODE_INIT_SECURITY
 	ZFS_AC_KERNEL_MOUNT_NODEV
+	ZFS_AC_KERNEL_SHRINK
 	ZFS_AC_KERNEL_BDI
 	ZFS_AC_KERNEL_BDI_SETUP_AND_REGISTER
 	ZFS_AC_KERNEL_SET_NLINK
diff --git a/configure b/configure
index d6f405bbb..f30b1ffcb 100755
--- a/configure
+++ b/configure
@@ -14774,6 +14774,144 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether sops->nr_cached_objects() exists" >&5
+$as_echo_n "checking whether sops->nr_cached_objects() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		int (*nr_cached_objects)(struct super_block *)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.nr_cached_objects = nr_cached_objects,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_NR_CACHED_OBJECTS 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
+	{ $as_echo "$as_me:$LINENO: checking whether sops->free_cached_objects() exists" >&5
+$as_echo_n "checking whether sops->free_cached_objects() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		void (*free_cached_objects)(struct super_block *, int)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.free_cached_objects = free_cached_objects,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_FREE_CACHED_OBJECTS 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol insert_inode_locked is exported" >&5
 $as_echo_n "checking whether symbol insert_inode_locked is exported... " >&6; }
 	grep -q -E '[[:space:]]insert_inode_locked[[:space:]]' \
@@ -15107,6 +15245,78 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether super_block has s_shrink" >&5
+$as_echo_n "checking whether super_block has s_shrink... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		int (*shrink)(struct shrinker *, struct shrink_control *sc)
+			__attribute__ ((unused)) = NULL;
+		struct super_block sb __attribute__ ((unused)) = {
+			.s_shrink.shrink = shrink,
+			.s_shrink.seeks = DEFAULT_SEEKS,
+			.s_shrink.batch = 0,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_SHRINK 1
+_ACEOF
+
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether super_block has s_bdi" >&5
 $as_echo_n "checking whether super_block has s_bdi... " >&6; }
 
@@ -19611,6 +19821,144 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether sops->nr_cached_objects() exists" >&5
+$as_echo_n "checking whether sops->nr_cached_objects() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		int (*nr_cached_objects)(struct super_block *)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.nr_cached_objects = nr_cached_objects,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_NR_CACHED_OBJECTS 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
+	{ $as_echo "$as_me:$LINENO: checking whether sops->free_cached_objects() exists" >&5
+$as_echo_n "checking whether sops->free_cached_objects() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		void (*free_cached_objects)(struct super_block *, int)
+			__attribute__ ((unused)) = NULL;
+		struct super_operations sops __attribute__ ((unused)) = {
+			.free_cached_objects = free_cached_objects,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_FREE_CACHED_OBJECTS 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol insert_inode_locked is exported" >&5
 $as_echo_n "checking whether symbol insert_inode_locked is exported... " >&6; }
 	grep -q -E '[[:space:]]insert_inode_locked[[:space:]]' \
@@ -19944,6 +20292,78 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether super_block has s_shrink" >&5
+$as_echo_n "checking whether super_block has s_shrink... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/fs.h>
+
+int
+main (void)
+{
+
+		int (*shrink)(struct shrinker *, struct shrink_control *sc)
+			__attribute__ ((unused)) = NULL;
+		struct super_block sb __attribute__ ((unused)) = {
+			.s_shrink.shrink = shrink,
+			.s_shrink.seeks = DEFAULT_SEEKS,
+			.s_shrink.batch = 0,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_SHRINK 1
+_ACEOF
+
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether super_block has s_bdi" >&5
 $as_echo_n "checking whether super_block has s_bdi... " >&6; }
 
diff --git a/dracut/90zfs/Makefile.in b/dracut/90zfs/Makefile.in
index cc7961812..ca1d86063 100644
--- a/dracut/90zfs/Makefile.in
+++ b/dracut/90zfs/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/dracut/Makefile.in b/dracut/Makefile.in
index 1c6b3e609..f385985d2 100644
--- a/dracut/Makefile.in
+++ b/dracut/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/etc/Makefile.in b/etc/Makefile.in
index a2e398604..481d0cdd6 100644
--- a/etc/Makefile.in
+++ b/etc/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/etc/init.d/Makefile.in b/etc/init.d/Makefile.in
index 9eb8ae7b4..f4d085485 100644
--- a/etc/init.d/Makefile.in
+++ b/etc/init.d/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/etc/zfs/Makefile.in b/etc/zfs/Makefile.in
index 6c81f5d8c..b421d59bc 100644
--- a/etc/zfs/Makefile.in
+++ b/etc/zfs/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/Makefile.in b/include/Makefile.in
index f82fdb267..18e235722 100644
--- a/include/Makefile.in
+++ b/include/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/linux/Makefile.in b/include/linux/Makefile.in
index e50b89b9b..030437b44 100644
--- a/include/linux/Makefile.in
+++ b/include/linux/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/sys/Makefile.in b/include/sys/Makefile.in
index b17649b02..012ffe9f7 100644
--- a/include/sys/Makefile.in
+++ b/include/sys/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/sys/arc.h b/include/sys/arc.h
index 8f189c62d..dd9b128bc 100644
--- a/include/sys/arc.h
+++ b/include/sys/arc.h
@@ -34,16 +34,27 @@ extern "C" {
 #include <sys/zio.h>
 #include <sys/dmu.h>
 #include <sys/spa.h>
+#include <sys/refcount.h>
 
 typedef struct arc_buf_hdr arc_buf_hdr_t;
 typedef struct arc_buf arc_buf_t;
+typedef struct arc_prune arc_prune_t;
 typedef void arc_done_func_t(zio_t *zio, arc_buf_t *buf, void *private);
+typedef void arc_prune_func_t(int64_t bytes, void *private);
 typedef int arc_evict_func_t(void *private);
 
 /* generic arc_done_func_t's which you can use */
 arc_done_func_t arc_bcopy_func;
 arc_done_func_t arc_getbuf_func;
 
+/* generic arc_prune_func_t wrapper for callbacks */
+struct arc_prune {
+	arc_prune_func_t	*p_pfunc;
+	void			*p_private;
+	list_node_t		p_node;
+	refcount_t		p_refcnt;
+};
+
 struct arc_buf {
 	arc_buf_hdr_t		*b_hdr;
 	arc_buf_t		*b_next;
@@ -113,9 +124,13 @@ zio_t *arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
     arc_done_func_t *ready, arc_done_func_t *done, void *private,
     int priority, int zio_flags, const zbookmark_t *zb);
 
+arc_prune_t *arc_add_prune_callback(arc_prune_func_t *func, void *private);
+void arc_remove_prune_callback(arc_prune_t *p);
+
 void arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private);
 int arc_buf_evict(arc_buf_t *buf);
 
+void arc_adjust_meta(int64_t adjustment, boolean_t may_prune);
 void arc_flush(spa_t *spa);
 void arc_tempreserve_clear(uint64_t reserve);
 int arc_tempreserve_space(uint64_t reserve, uint64_t txg);
diff --git a/include/sys/fm/Makefile.in b/include/sys/fm/Makefile.in
index e3fd84cfd..932e5e732 100644
--- a/include/sys/fm/Makefile.in
+++ b/include/sys/fm/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/sys/fm/fs/Makefile.in b/include/sys/fm/fs/Makefile.in
index 40952616b..bbcb1c258 100644
--- a/include/sys/fm/fs/Makefile.in
+++ b/include/sys/fm/fs/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/sys/fs/Makefile.in b/include/sys/fs/Makefile.in
index db73ab862..da86a6fbc 100644
--- a/include/sys/fs/Makefile.in
+++ b/include/sys/fs/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/include/sys/zfs_vfsops.h b/include/sys/zfs_vfsops.h
index 6d4d713ce..b7badeed8 100644
--- a/include/sys/zfs_vfsops.h
+++ b/include/sys/zfs_vfsops.h
@@ -67,7 +67,8 @@ typedef struct zfs_sb {
 	boolean_t	z_unmounted;	/* unmounted */
 	rrwlock_t	z_teardown_lock;
 	krwlock_t	z_teardown_inactive_lock;
-	list_t		z_all_znodes;	/* all vnodes in the fs */
+	list_t		z_all_znodes;	/* all znodes in the fs */
+	uint64_t	z_nr_znodes;	/* number of znodes in the fs */
 	kmutex_t	z_znodes_lock;	/* lock for z_all_znodes */
 	struct inode	*z_ctldir;	/* .zfs directory inode */
 	boolean_t	z_show_ctldir;	/* expose .zfs in the root dir */
@@ -185,6 +186,8 @@ extern int zfs_get_zplprop(objset_t *os, zfs_prop_t prop,
 extern int zfs_sb_create(const char *name, zfs_sb_t **zsbp);
 extern int zfs_sb_setup(zfs_sb_t *zsb, boolean_t mounting);
 extern void zfs_sb_free(zfs_sb_t *zsb);
+extern int zfs_sb_prune(struct super_block *sb, unsigned long nr_to_scan,
+    int *objects);
 extern int zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting);
 extern int zfs_check_global_label(const char *dsname, const char *hexsl);
 extern boolean_t zfs_is_readonly(zfs_sb_t *zsb);
diff --git a/include/sys/zpl.h b/include/sys/zpl.h
index 0aacce8bd..2195ec9a3 100644
--- a/include/sys/zpl.h
+++ b/include/sys/zpl.h
@@ -48,6 +48,8 @@ extern const struct file_operations zpl_file_operations;
 extern const struct file_operations zpl_dir_file_operations;
 
 /* zpl_super.c */
+extern void zpl_prune_sbs(int64_t bytes_to_scan, void *private);
+
 typedef struct zpl_mount_data {
 	const char *z_osname;	/* Dataset name */
 	void *z_data;		/* Mount options string */
diff --git a/lib/Makefile.in b/lib/Makefile.in
index 17f84a548..5929cc468 100644
--- a/lib/Makefile.in
+++ b/lib/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libavl/Makefile.in b/lib/libavl/Makefile.in
index 55bb04d9f..9a6ea3a75 100644
--- a/lib/libavl/Makefile.in
+++ b/lib/libavl/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libefi/Makefile.in b/lib/libefi/Makefile.in
index 6e4a83b3c..7abee8cab 100644
--- a/lib/libefi/Makefile.in
+++ b/lib/libefi/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libnvpair/Makefile.in b/lib/libnvpair/Makefile.in
index 60439aece..33d3f3b1d 100644
--- a/lib/libnvpair/Makefile.in
+++ b/lib/libnvpair/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libshare/Makefile.in b/lib/libshare/Makefile.in
index 94ea82e90..67d23d279 100644
--- a/lib/libshare/Makefile.in
+++ b/lib/libshare/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/Makefile.in b/lib/libspl/Makefile.in
index 194679a93..db3499a6d 100644
--- a/lib/libspl/Makefile.in
+++ b/lib/libspl/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/asm-generic/Makefile.in b/lib/libspl/asm-generic/Makefile.in
index a9ffb578c..cae5d5678 100644
--- a/lib/libspl/asm-generic/Makefile.in
+++ b/lib/libspl/asm-generic/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/asm-i386/Makefile.in b/lib/libspl/asm-i386/Makefile.in
index ca6573040..652782e66 100644
--- a/lib/libspl/asm-i386/Makefile.in
+++ b/lib/libspl/asm-i386/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/asm-x86_64/Makefile.in b/lib/libspl/asm-x86_64/Makefile.in
index 2db49b35a..ad6c870dc 100644
--- a/lib/libspl/asm-x86_64/Makefile.in
+++ b/lib/libspl/asm-x86_64/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/Makefile.in b/lib/libspl/include/Makefile.in
index d7a8f52fc..419041afa 100644
--- a/lib/libspl/include/Makefile.in
+++ b/lib/libspl/include/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/ia32/Makefile.in b/lib/libspl/include/ia32/Makefile.in
index b60892865..c0418ee60 100644
--- a/lib/libspl/include/ia32/Makefile.in
+++ b/lib/libspl/include/ia32/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/ia32/sys/Makefile.in b/lib/libspl/include/ia32/sys/Makefile.in
index 36629967e..86b08fd79 100644
--- a/lib/libspl/include/ia32/sys/Makefile.in
+++ b/lib/libspl/include/ia32/sys/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/rpc/Makefile.in b/lib/libspl/include/rpc/Makefile.in
index 68e3c2f12..92529aecf 100644
--- a/lib/libspl/include/rpc/Makefile.in
+++ b/lib/libspl/include/rpc/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/sys/Makefile.in b/lib/libspl/include/sys/Makefile.in
index 6851505dd..09e1ec957 100644
--- a/lib/libspl/include/sys/Makefile.in
+++ b/lib/libspl/include/sys/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/sys/dktp/Makefile.in b/lib/libspl/include/sys/dktp/Makefile.in
index 89c3285e1..84961afae 100644
--- a/lib/libspl/include/sys/dktp/Makefile.in
+++ b/lib/libspl/include/sys/dktp/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/sys/sysevent/Makefile.in b/lib/libspl/include/sys/sysevent/Makefile.in
index de9db421b..5d6a93dbe 100644
--- a/lib/libspl/include/sys/sysevent/Makefile.in
+++ b/lib/libspl/include/sys/sysevent/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libspl/include/util/Makefile.in b/lib/libspl/include/util/Makefile.in
index d7cd17c15..068a2f560 100644
--- a/lib/libspl/include/util/Makefile.in
+++ b/lib/libspl/include/util/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libunicode/Makefile.in b/lib/libunicode/Makefile.in
index f6c8690cd..fbcb32b99 100644
--- a/lib/libunicode/Makefile.in
+++ b/lib/libunicode/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libuutil/Makefile.in b/lib/libuutil/Makefile.in
index d44bba2d6..6507a7ead 100644
--- a/lib/libuutil/Makefile.in
+++ b/lib/libuutil/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libzfs/Makefile.in b/lib/libzfs/Makefile.in
index 29642b1ac..a975a193f 100644
--- a/lib/libzfs/Makefile.in
+++ b/lib/libzfs/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/lib/libzpool/Makefile.in b/lib/libzpool/Makefile.in
index 0e46c1516..5e1fded91 100644
--- a/lib/libzpool/Makefile.in
+++ b/lib/libzpool/Makefile.in
@@ -71,6 +71,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/man/Makefile.in b/man/Makefile.in
index 84c6c1706..1ad3c35fd 100644
--- a/man/Makefile.in
+++ b/man/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/man/man8/Makefile.in b/man/man8/Makefile.in
index be187c9c0..86e691d2e 100644
--- a/man/man8/Makefile.in
+++ b/man/man8/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index f71c24844..95d14a9e7 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -104,6 +104,14 @@
  * protected from simultaneous callbacks from arc_buf_evict()
  * and arc_do_user_evicts().
  *
+ * It as also possible to register a callback which is run when the
+ * arc_meta_limit is reached and no buffers can be safely evicted.  In
+ * this case the arc user should drop a reference on some arc buffers so
+ * they can be reclaimed and the arc_meta_limit honored.  For example,
+ * when using the ZPL each dentry holds a references on a znode.  These
+ * dentries must be pruned before the arc buffer holding the znode can
+ * be safely evicted.
+ *
  * Note that the majority of the performance stats are manipulated
  * with atomic operations.
  *
@@ -120,14 +128,13 @@
 #include <sys/zio.h>
 #include <sys/zfs_context.h>
 #include <sys/arc.h>
-#include <sys/refcount.h>
 #include <sys/vdev.h>
 #include <sys/vdev_impl.h>
 #ifdef _KERNEL
 #include <sys/vmsystm.h>
 #include <vm/anon.h>
 #include <sys/fs/swapnode.h>
-#include <sys/dnlc.h>
+#include <sys/zpl.h>
 #endif
 #include <sys/callb.h>
 #include <sys/kstat.h>
@@ -141,8 +148,8 @@ extern int zfs_write_limit_shift;
 extern uint64_t zfs_write_limit_max;
 extern kmutex_t zfs_write_limit_lock;
 
-#define	ARC_REDUCE_DNLC_PERCENT	3
-uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
+/* number of bytes to prune from caches when at arc_meta_limit is reached */
+uint_t arc_meta_prune = 1048576;
 
 typedef enum arc_reclaim_strategy {
 	ARC_RECLAIM_AGGR,		/* Aggressive reclaim strategy */
@@ -180,7 +187,7 @@ unsigned long zfs_arc_meta_limit = 0;
 int zfs_arc_grow_retry = 0;
 int zfs_arc_shrink_shift = 0;
 int zfs_arc_p_min_shift = 0;
-int zfs_arc_reduce_dnlc_percent = 0;
+int zfs_arc_meta_prune = 0;
 
 /*
  * Note that buffers can be in one of 6 states:
@@ -288,6 +295,7 @@ typedef struct arc_stats {
 	kstat_named_t arcstat_no_grow;
 	kstat_named_t arcstat_tempreserve;
 	kstat_named_t arcstat_loaned_bytes;
+	kstat_named_t arcstat_prune;
 	kstat_named_t arcstat_meta_used;
 	kstat_named_t arcstat_meta_limit;
 	kstat_named_t arcstat_meta_max;
@@ -352,6 +360,7 @@ static arc_stats_t arc_stats = {
 	{ "arc_no_grow",		KSTAT_DATA_UINT64 },
 	{ "arc_tempreserve",		KSTAT_DATA_UINT64 },
 	{ "arc_loaned_bytes",		KSTAT_DATA_UINT64 },
+	{ "arc_prune",			KSTAT_DATA_UINT64 },
 	{ "arc_meta_used",		KSTAT_DATA_UINT64 },
 	{ "arc_meta_limit",		KSTAT_DATA_UINT64 },
 	{ "arc_meta_max",		KSTAT_DATA_UINT64 },
@@ -481,6 +490,8 @@ struct arc_buf_hdr {
 	list_node_t		b_l2node;
 };
 
+static list_t arc_prune_list;
+static kmutex_t arc_prune_mtx;
 static arc_buf_t *arc_eviction_list;
 static kmutex_t arc_eviction_mtx;
 static arc_buf_hdr_t arc_eviction_hdr;
@@ -1925,6 +1936,48 @@ arc_adjust(void)
 	}
 }
 
+/*
+ * Request that arc user drop references so that N bytes can be released
+ * from the cache.  This provides a mechanism to ensure the arc can honor
+ * the arc_meta_limit and reclaim buffers which are pinned in the cache
+ * by higher layers.  (i.e. the zpl)
+ */
+static void
+arc_do_user_prune(int64_t adjustment)
+{
+	arc_prune_func_t *func;
+	void *private;
+	arc_prune_t *cp, *np;
+
+	mutex_enter(&arc_prune_mtx);
+
+	cp = list_head(&arc_prune_list);
+	while (cp != NULL) {
+		func = cp->p_pfunc;
+		private = cp->p_private;
+		np = list_next(&arc_prune_list, cp);
+		refcount_add(&cp->p_refcnt, func);
+		mutex_exit(&arc_prune_mtx);
+
+		if (func != NULL)
+			func(adjustment, private);
+
+		mutex_enter(&arc_prune_mtx);
+
+		/* User removed prune callback concurrently with execution */
+		if (refcount_remove(&cp->p_refcnt, func) == 0) {
+			ASSERT(!list_link_active(&cp->p_node));
+			refcount_destroy(&cp->p_refcnt);
+			kmem_free(cp, sizeof (*cp));
+		}
+
+		cp = np;
+	}
+
+	ARCSTAT_BUMP(arcstat_prune);
+	mutex_exit(&arc_prune_mtx);
+}
+
 static void
 arc_do_user_evicts(void)
 {
@@ -1949,6 +2002,32 @@ arc_do_user_evicts(void)
 }
 
 /*
+ * Evict only meta data objects from the cache leaving the data objects.
+ * This is only used to enforce the tunable arc_meta_limit, if we are
+ * unable to evict enough buffers notify the user via the prune callback.
+ */
+void
+arc_adjust_meta(int64_t adjustment, boolean_t may_prune)
+{
+	int64_t delta;
+
+	if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
+		delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
+		arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_METADATA);
+		adjustment -= delta;
+	}
+
+	if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
+		delta = MIN(arc_mfu->arcs_lsize[ARC_BUFC_METADATA], adjustment);
+		arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_METADATA);
+		adjustment -= delta;
+	}
+
+	if (may_prune && (adjustment > 0) && (arc_meta_used > arc_meta_limit))
+		arc_do_user_prune(arc_meta_prune);
+}
+
+/*
  * Flush all *evictable* data from the cache for the given spa.
  * NOTE: this will not touch "active" (i.e. referenced) data.
  */
@@ -2085,24 +2164,6 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat)
 	kmem_cache_t		*prev_data_cache = NULL;
 	extern kmem_cache_t	*zio_buf_cache[];
 	extern kmem_cache_t	*zio_data_buf_cache[];
-#ifdef _KERNEL
-	int			retry = 0;
-
-	while ((arc_meta_used >= arc_meta_limit) && (retry < 10)) {
-		/*
-		 * We are exceeding our meta-data cache limit.
-		 * Purge some DNLC entries to release holds on meta-data.
-		 */
-		dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
-		retry++;
-	}
-#if defined(__i386)
-	/*
-	 * Reclaim unused memory from all kmem caches.
-	 */
-	kmem_reap();
-#endif
-#endif
 
 	/*
 	 * An aggressive reclamation will shrink the cache size as well as
@@ -2121,6 +2182,7 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat)
 			kmem_cache_reap_now(zio_data_buf_cache[i]);
 		}
 	}
+
 	kmem_cache_reap_now(buf_cache);
 	kmem_cache_reap_now(hdr_cache);
 }
@@ -2131,6 +2193,7 @@ arc_reclaim_thread(void)
 	clock_t			growtime = 0;
 	arc_reclaim_strategy_t	last_reclaim = ARC_RECLAIM_CONS;
 	callb_cpr_t		cpr;
+	int64_t			prune;
 
 	CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
 
@@ -2160,9 +2223,14 @@ arc_reclaim_thread(void)
 			arc_no_grow = FALSE;
 		}
 
-		/* Keep meta data usage within limits */
-		if (arc_meta_used >= arc_meta_limit)
-			arc_kmem_reap_now(ARC_RECLAIM_CONS);
+		/*
+		 * Keep meta data usage within limits, arc_shrink() is not
+		 * used to avoid collapsing the arc_c value when only the
+		 * arc_meta_limit is being exceeded.
+		 */
+		prune = (int64_t)arc_meta_used - (int64_t)arc_meta_limit;
+		if (prune > 0)
+			arc_adjust_meta(prune, B_TRUE);
 
 		arc_adjust();
 
@@ -2399,16 +2467,27 @@ arc_get_data_buf(arc_buf_t *buf)
 		state =  (arc_mru->arcs_lsize[type] >= size &&
 		    mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
 	}
+
 	if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
 		if (type == ARC_BUFC_METADATA) {
 			buf->b_data = zio_buf_alloc(size);
 			arc_space_consume(size, ARC_SPACE_DATA);
+
+			/*
+			 * If we are unable to recycle an existing meta buffer
+			 * signal the reclaim thread.  It will notify users
+			 * via the prune callback to drop references.  The
+			 * prune callback in run in the context of the reclaim
+			 * thread to avoid deadlocking on the hash_lock.
+			 */
+			cv_signal(&arc_reclaim_thr_cv);
 		} else {
 			ASSERT(type == ARC_BUFC_DATA);
 			buf->b_data = zio_data_buf_alloc(size);
 			ARCSTAT_INCR(arcstat_data_size, size);
 			atomic_add_64(&arc_size, size);
 		}
+
 		ARCSTAT_BUMP(arcstat_recycle_miss);
 	}
 	ASSERT(buf->b_data != NULL);
@@ -3021,6 +3100,37 @@ top:
 	return (0);
 }
 
+arc_prune_t *
+arc_add_prune_callback(arc_prune_func_t *func, void *private)
+{
+	arc_prune_t *p;
+
+	p = kmem_alloc(sizeof(*p), KM_SLEEP);
+	p->p_pfunc = func;
+	p->p_private = private;
+	list_link_init(&p->p_node);
+	refcount_create(&p->p_refcnt);
+
+	mutex_enter(&arc_prune_mtx);
+	refcount_add(&p->p_refcnt, &arc_prune_list);
+	list_insert_head(&arc_prune_list, p);
+	mutex_exit(&arc_prune_mtx);
+
+	return (p);
+}
+
+void
+arc_remove_prune_callback(arc_prune_t *p)
+{
+	mutex_enter(&arc_prune_mtx);
+	list_remove(&arc_prune_list, p);
+	if (refcount_remove(&p->p_refcnt, &arc_prune_list) == 0) {
+		refcount_destroy(&p->p_refcnt);
+		kmem_free(p, sizeof (*p));
+	}
+	mutex_exit(&arc_prune_mtx);
+}
+
 void
 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
 {
@@ -3598,8 +3708,8 @@ arc_init(void)
 	if (zfs_arc_p_min_shift > 0)
 		arc_p_min_shift = zfs_arc_p_min_shift;
 
-	if (zfs_arc_reduce_dnlc_percent > 0)
-		arc_reduce_dnlc_percent = zfs_arc_reduce_dnlc_percent;
+	if (zfs_arc_meta_prune > 0)
+		arc_meta_prune = zfs_arc_meta_prune;
 
 	/* if kmem_flags are set, lets try to use less memory */
 	if (kmem_debugging())
@@ -3646,7 +3756,10 @@ arc_init(void)
 	buf_init();
 
 	arc_thread_exit = 0;
+	list_create(&arc_prune_list, sizeof (arc_prune_t),
+	    offsetof(arc_prune_t, p_node));
 	arc_eviction_list = NULL;
+	mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
 	bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
 
@@ -3674,6 +3787,8 @@ arc_init(void)
 void
 arc_fini(void)
 {
+	arc_prune_t *p;
+
 	mutex_enter(&arc_reclaim_thr_lock);
 #ifdef _KERNEL
 	spl_unregister_shrinker(&arc_shrinker);
@@ -3693,6 +3808,17 @@ arc_fini(void)
 		arc_ksp = NULL;
 	}
 
+	mutex_enter(&arc_prune_mtx);
+	while ((p = list_head(&arc_prune_list)) != NULL) {
+		list_remove(&arc_prune_list, p);
+		refcount_remove(&p->p_refcnt, &arc_prune_list);
+		refcount_destroy(&p->p_refcnt);
+		kmem_free(p, sizeof (*p));
+	}
+	mutex_exit(&arc_prune_mtx);
+
+	list_destroy(&arc_prune_list);
+	mutex_destroy(&arc_prune_mtx);
 	mutex_destroy(&arc_eviction_mtx);
 	mutex_destroy(&arc_reclaim_thr_lock);
 	cv_destroy(&arc_reclaim_thr_cv);
@@ -4774,6 +4900,8 @@ l2arc_stop(void)
 EXPORT_SYMBOL(arc_read);
 EXPORT_SYMBOL(arc_buf_remove_ref);
 EXPORT_SYMBOL(arc_getbuf_func);
+EXPORT_SYMBOL(arc_add_prune_callback);
+EXPORT_SYMBOL(arc_remove_prune_callback);
 
 module_param(zfs_arc_min, ulong, 0444);
 MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
@@ -4784,8 +4912,8 @@ MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
 module_param(zfs_arc_meta_limit, ulong, 0444);
 MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
 
-module_param(zfs_arc_reduce_dnlc_percent, int, 0444);
-MODULE_PARM_DESC(zfs_arc_reduce_dnlc_percent, "Meta reclaim percentage");
+module_param(zfs_arc_meta_prune, int, 0444);
+MODULE_PARM_DESC(zfs_arc_meta_prune, "Bytes of meta data to prune");
 
 module_param(zfs_arc_grow_retry, int, 0444);
 MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index a0726e117..fb319a547 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -986,6 +986,26 @@ zfs_root(zfs_sb_t *zsb, struct inode **ipp)
 }
 EXPORT_SYMBOL(zfs_root);
 
+#ifdef HAVE_SHRINK
+int
+zfs_sb_prune(struct super_block *sb, unsigned long nr_to_scan, int *objects)
+{
+	zfs_sb_t *zsb = sb->s_fs_info;
+	struct shrinker *shrinker = &sb->s_shrink;
+	struct shrink_control sc = {
+		.nr_to_scan = nr_to_scan,
+		.gfp_mask = GFP_KERNEL,
+	};
+
+	ZFS_ENTER(zsb);
+	*objects = (*shrinker->shrink)(shrinker, &sc);
+	ZFS_EXIT(zsb);
+
+	return (0);
+}
+EXPORT_SYMBOL(zfs_sb_prune);
+#endif /* HAVE_SHRINK */
+
 /*
  * Teardown the zfs_sb_t::z_os.
  *
@@ -1533,6 +1553,7 @@ zfs_init(void)
 	zfs_znode_init();
 	dmu_objset_register_type(DMU_OST_ZFS, zfs_space_delta_cb);
 	register_filesystem(&zpl_fs_type);
+	(void) arc_add_prune_callback(zpl_prune_sbs, NULL);
 }
 
 void
diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index a35e3b5f2..709ae74f8 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -269,6 +269,7 @@ zfs_inode_destroy(struct inode *ip)
 
 	mutex_enter(&zsb->z_znodes_lock);
 	list_remove(&zsb->z_all_znodes, zp);
+	zsb->z_nr_znodes--;
 	mutex_exit(&zsb->z_znodes_lock);
 
 	if (zp->z_acl_cached) {
@@ -401,6 +402,7 @@ zfs_znode_alloc(zfs_sb_t *zsb, dmu_buf_t *db, int blksz,
 
 	mutex_enter(&zsb->z_znodes_lock);
 	list_insert_tail(&zsb->z_all_znodes, zp);
+	zsb->z_nr_znodes++;
 	membar_producer();
 	mutex_exit(&zsb->z_znodes_lock);
 
diff --git a/module/zfs/zpl_super.c b/module/zfs/zpl_super.c
index 650e9c0d3..3abb26a9e 100644
--- a/module/zfs/zpl_super.c
+++ b/module/zfs/zpl_super.c
@@ -199,34 +199,120 @@ zpl_kill_sb(struct super_block *sb)
 	kill_anon_super(sb);
 }
 
+#ifdef HAVE_SHRINK
+/*
+ * Linux 3.1 - 3.x API
+ *
+ * The Linux 3.1 API introduced per-sb cache shrinkers to replace the
+ * global ones.  This allows us a mechanism to cleanly target a specific
+ * zfs file system when the dnode and inode caches grow too large.
+ *
+ * In addition, the 3.0 kernel added the iterate_supers_type() helper
+ * function which is used to safely walk all of the zfs file systems.
+ */
+static void
+zpl_prune_sb(struct super_block *sb, void *arg)
+{
+	int objects = 0;
+	int error;
+
+	error = -zfs_sb_prune(sb, *(unsigned long *)arg, &objects);
+	ASSERT3S(error, <=, 0);
+
+	return;
+}
+
+void
+zpl_prune_sbs(int64_t bytes_to_scan, void *private)
+{
+	unsigned long nr_to_scan = (bytes_to_scan / sizeof(znode_t));
+
+	iterate_supers_type(&zpl_fs_type, zpl_prune_sb, &nr_to_scan);
+	kmem_reap();
+}
+#else
+/*
+ * Linux 2.6.x - 3.0 API
+ *
+ * These are best effort interfaces are provided by the SPL to induce
+ * the Linux VM subsystem to reclaim a fraction of the both dnode and
+ * inode caches.  Ideally, we want to just target the zfs file systems
+ * however our only option is to reclaim from them all.
+ */
+void
+zpl_prune_sbs(int64_t bytes_to_scan, void *private)
+{
+	unsigned long nr_to_scan = (bytes_to_scan / sizeof(znode_t));
+
+        shrink_dcache_memory(nr_to_scan, GFP_KERNEL);
+        shrink_icache_memory(nr_to_scan, GFP_KERNEL);
+        kmem_reap();
+}
+#endif /* HAVE_SHRINK */
+
+#ifdef HAVE_NR_CACHED_OBJECTS
+static int
+zpl_nr_cached_objects(struct super_block *sb)
+{
+	zfs_sb_t *zsb = sb->s_fs_info;
+	int nr;
+
+	mutex_enter(&zsb->z_znodes_lock);
+	nr = zsb->z_nr_znodes;
+	mutex_exit(&zsb->z_znodes_lock);
+
+	return (nr);
+}
+#endif /* HAVE_NR_CACHED_OBJECTS */
+
+#ifdef HAVE_FREE_CACHED_OBJECTS
+/*
+ * Attempt to evict some meta data from the cache.  The ARC operates in
+ * terms of bytes while the Linux VFS uses objects.  Now because this is
+ * just a best effort eviction and the exact values aren't critical so we
+ * extrapolate from an object count to a byte size using the znode_t size.
+ */
+static void
+zpl_free_cached_objects(struct super_block *sb, int nr_to_scan)
+{
+	arc_adjust_meta(nr_to_scan * sizeof(znode_t), B_FALSE);
+}
+#endif /* HAVE_FREE_CACHED_OBJECTS */
+
 const struct super_operations zpl_super_operations = {
-	.alloc_inode	= zpl_inode_alloc,
-	.destroy_inode	= zpl_inode_destroy,
-	.dirty_inode	= NULL,
-	.write_inode	= NULL,
-	.drop_inode	= NULL,
+	.alloc_inode		= zpl_inode_alloc,
+	.destroy_inode		= zpl_inode_destroy,
+	.dirty_inode		= NULL,
+	.write_inode		= NULL,
+	.drop_inode		= NULL,
 #ifdef HAVE_EVICT_INODE
-	.evict_inode	= zpl_evict_inode,
+	.evict_inode		= zpl_evict_inode,
 #else
-	.clear_inode	= zpl_clear_inode,
-	.delete_inode	= zpl_inode_delete,
+	.clear_inode		= zpl_clear_inode,
+	.delete_inode		= zpl_inode_delete,
 #endif /* HAVE_EVICT_INODE */
-	.put_super	= zpl_put_super,
-	.write_super	= NULL,
-	.sync_fs	= zpl_sync_fs,
-	.statfs		= zpl_statfs,
-	.remount_fs	= zpl_remount_fs,
-	.show_options	= zpl_show_options,
-	.show_stats	= NULL,
+	.put_super		= zpl_put_super,
+	.write_super		= NULL,
+	.sync_fs		= zpl_sync_fs,
+	.statfs			= zpl_statfs,
+	.remount_fs		= zpl_remount_fs,
+	.show_options		= zpl_show_options,
+	.show_stats		= NULL,
+#ifdef HAVE_NR_CACHED_OBJECTS
+	.nr_cached_objects	= zpl_nr_cached_objects,
+#endif /* HAVE_NR_CACHED_OBJECTS */
+#ifdef HAVE_FREE_CACHED_OBJECTS
+	.free_cached_objects	= zpl_free_cached_objects,
+#endif /* HAVE_FREE_CACHED_OBJECTS */
 };
 
 struct file_system_type zpl_fs_type = {
-	.owner		= THIS_MODULE,
-	.name		= ZFS_DRIVER,
+	.owner			= THIS_MODULE,
+	.name			= ZFS_DRIVER,
 #ifdef HAVE_MOUNT_NODEV
-	.mount		= zpl_mount,
+	.mount			= zpl_mount,
 #else
-	.get_sb		= zpl_get_sb,
+	.get_sb			= zpl_get_sb,
 #endif /* HAVE_MOUNT_NODEV */
-	.kill_sb	= zpl_kill_sb,
+	.kill_sb		= zpl_kill_sb,
 };
diff --git a/scripts/Makefile.in b/scripts/Makefile.in
index 5115a9e0b..4fdc85b67 100644
--- a/scripts/Makefile.in
+++ b/scripts/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/scripts/zpios-profile/Makefile.in b/scripts/zpios-profile/Makefile.in
index 1c59d7475..339062111 100644
--- a/scripts/zpios-profile/Makefile.in
+++ b/scripts/zpios-profile/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/scripts/zpios-test/Makefile.in b/scripts/zpios-test/Makefile.in
index fb1114530..1adbef8cf 100644
--- a/scripts/zpios-test/Makefile.in
+++ b/scripts/zpios-test/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/scripts/zpool-config/Makefile.in b/scripts/zpool-config/Makefile.in
index 2c4fcb976..c78e79667 100644
--- a/scripts/zpool-config/Makefile.in
+++ b/scripts/zpool-config/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/scripts/zpool-layout/Makefile.in b/scripts/zpool-layout/Makefile.in
index bebd47b8f..59034e069 100644
--- a/scripts/zpool-layout/Makefile.in
+++ b/scripts/zpool-layout/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/udev/Makefile.in b/udev/Makefile.in
index 856d11aaf..6232f65db 100644
--- a/udev/Makefile.in
+++ b/udev/Makefile.in
@@ -69,6 +69,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/udev/rules.d/Makefile.in b/udev/rules.d/Makefile.in
index 37eb4c732..f9a72cfb6 100644
--- a/udev/rules.d/Makefile.in
+++ b/udev/rules.d/Makefile.in
@@ -70,6 +70,7 @@ am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/kernel-rq-is_sync.m4 \
 	$(top_srcdir)/config/kernel-security-inode-init.m4 \
 	$(top_srcdir)/config/kernel-set-nlink.m4 \
+	$(top_srcdir)/config/kernel-shrink.m4 \
 	$(top_srcdir)/config/kernel-truncate-setsize.m4 \
 	$(top_srcdir)/config/kernel-xattr-handler.m4 \
 	$(top_srcdir)/config/kernel.m4 \
diff --git a/zfs_config.h.in b/zfs_config.h.in
index e0f746704..b53ca52d7 100644
--- a/zfs_config.h.in
+++ b/zfs_config.h.in
@@ -90,6 +90,9 @@
 /* kernel defines fmode_t */
 #undef HAVE_FMODE_T
 
+/* sops->free_cached_objects() exists */
+#undef HAVE_FREE_CACHED_OBJECTS
+
 /* fops->fsync() with range */
 #undef HAVE_FSYNC_RANGE
 
@@ -141,6 +144,9 @@
 /* mount_nodev() is available */
 #undef HAVE_MOUNT_NODEV
 
+/* sops->nr_cached_objects() exists */
+#undef HAVE_NR_CACHED_OBJECTS
+
 /* open_bdev_exclusive() is available */
 #undef HAVE_OPEN_BDEV_EXCLUSIVE
 
@@ -156,6 +162,9 @@
 /* set_nlink() is available */
 #undef HAVE_SET_NLINK
 
+/* struct super_block has s_shrink */
+#undef HAVE_SHRINK
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #undef HAVE_STDINT_H