mm: process/cgroup ksm support

So far KSM can only be enabled by calling madvise for memory regions. To be able to use KSM for more workloads, KSM needs to have the ability to be enabled / disabled at the process / cgroup level.

Use case 1:
The madvise call is not available in the programming language. An example for this are programs with forked workloads using a garbage collected language without pointers. In such a language madvise cannot be made available.

In addition the addresses of objects get moved around as they are garbage collected. KSM sharing needs to be enabled "from the outside" for these type of workloads.

Use case 2:
The same interpreter can also be used for workloads where KSM brings no benefit or even has overhead. We'd like to be able to enable KSM on a workload by workload basis.

Use case 3:
With the madvise call sharing opportunities are only enabled for the current
process: it is a workload-local decision. A considerable number of sharing opportunities may exist across multiple workloads or jobs (if they are part of the same security domain). Only a higler level entity like a job scheduler or container can know for certain if its running one or more instances of a job. That job scheduler however doesn't have the necessary internal workload knowledge to make targeted madvise calls.

Security concerns:
In previous discussions security concerns have been brought up. The problem is that an individual workload does not have the knowledge about what else is running on a machine. Therefore it has to be very conservative in what memory areas can be shared or not. However, if the system is dedicated to running multiple jobs within the same security domain, its the job scheduler that has the knowledge that sharing can be safely enabled and is even desirable.

Performance:
Experiments with using UKSM have shown a capacity increase of around 20%.

1. New options for prctl system command
This patch series adds two new options to the prctl system call. The first one allows to enable KSM at the process level and the second one to query the setting.

The setting will be inherited by child processes.

With the above setting, KSM can be enabled for the seed process of a cgroup and all processes in the cgroup will inherit the setting.

2. Changes to KSM processing
When KSM is enabled at the process level, the KSM code will iterate over all the VMA's and enable KSM for the eligible VMA's.

When forking a process that has KSM enabled, the setting will be inherited by the new child process.

In addition when KSM is disabled for a process, KSM will be disabled for the VMA's where KSM has been enabled.

3. Add general_profit metric
The general_profit metric of KSM is specified in the documentation, but not calculated. This adds the general profit metric to /sys/kernel/debug/mm/ksm.

4. Add more metrics to ksm_stat
This adds the process profit and ksm type metric to /proc/<pid>/ksm_stat.

5. Add more tests to ksm_tests
This adds an option to specify the merge type to the ksm_tests. This allows to test madvise and prctl KSM. It also adds a new option to query if prctl KSM has been enabled. It adds a fork test to verify that the KSM process setting is inherited by client processes.

Changes:
- V5:
- When the prctl system call is invoked, mark all compatible VMA as mergeable
- Instead of checcking during scan if VMA is mergeable, mark the VMA mergeable when the VMA is created (in case the VMA is compatible)
- Remove earlier changes, they are no longer necessary
- Unset the flag MMF_VM_MERGE_ANY in gmap_mark_unmergeable().
- When unsetting the MMF_VM_MERGE_ANY flag with prctl, only unset the flag
- Remove pages_volatile function (with the simplar general_profit calculation, the function is no longer needed)
- Use simpler formula for calculation of general_profit

- V4:
- removing check in prctl for MMF_VM_MERGEABLE in PR_SET_MEMORY_MERGE handling
- Checking for VM_MERGEABLE AND MMF_VM_MERGE_ANY to avoid chaning vm_flags
- This requires also checking that the vma is compatible. The compatibility check is provided by a new helper
- processes which have set MMF_VM_MERGE_ANY, only need to call the helper and not madvise.
- removed unmerge_vmas function, this function is no longer necessary, clearing the MMF_VM_MERGE_ANY bit is sufficient

- V3:
- folded patch 1 - 6
- folded patch 7 - 14
- folded patch 15 - 19
- Expanded on the use cases in the cover letter
- Added a section on security concerns to the cover letter

- V2:
- Added use cases to the cover letter
- Removed the tracing patch from the patch series and posted it as an individual patch
- Refreshed repo

Stefan Roesch (3):
mm: add new api to enable ksm per process
mm: add new KSM process and sysfs knobs
selftests/mm: add new selftests for KSM

 Documentation/ABI/testing/sysfs-kernel-mm-ksm |   8 +
 Documentation/admin-guide/mm/ksm.rst          |   8 +-
 arch/s390/mm/gmap.c                           |   1 +
 fs/proc/base.c                                |   5 +
 include/linux/ksm.h                           |  36 ++-
 include/linux/sched/coredump.h                |   1 +
 include/uapi/linux/prctl.h                    |   2 +
 kernel/fork.c                                 |   1 +
 kernel/sys.c                                  |  24 ++
 mm/ksm.c                                      | 143 ++++++++--
 mm/mmap.c                                     |   7 +
 tools/include/uapi/linux/prctl.h              |   2 +
 tools/testing/selftests/mm/Makefile           |   2 +-
 tools/testing/selftests/mm/ksm_tests.c        | 254 +++++++++++++++---
 14 files changed, 426 insertions(+), 68 deletions(-)

2.34.1

So far KSM can only be enabled by calling madvise for memory regions. To be able to use KSM for more workloads, KSM needs to have the ability to be enabled / disabled at the process / cgroup level.

1. New options for prctl system command

This patch series adds two new options to the prctl system call. The first one allows to enable KSM at the process level and the second one to query the setting.

The setting will be inherited by child processes.

With the above setting, KSM can be enabled for the seed process of a cgroup and all processes in the cgroup will inherit the setting.

2. Changes to KSM processing

When KSM is enabled at the process level, the KSM code will iterate over all the VMA's and enable KSM for the eligible VMA's.

When forking a process that has KSM enabled, the setting will be inherited by the new child process.

1) Introduce new MMF_VM_MERGE_ANY flag

This introduces the new flag MMF_VM_MERGE_ANY flag. When this flag is set, kernel samepage merging (ksm) gets enabled for all vma's of a process.

2) Setting VM_MERGEABLE on VMA creation

When a VMA is created, if the MMF_VM_MERGE_ANY flag is set, the VM_MERGEABLE flag will be set for this VMA.

3) add flag to __ksm_enter

This change adds the flag parameter to __ksm_enter. This allows to distinguish if ksm was called by prctl or madvise.

4) add flag to __ksm_exit call

This adds the flag parameter to the __ksm_exit() call. This allows to distinguish if this call is for an prctl or madvise invocation.

5) support disabling of ksm for a process

This adds the ability to disable ksm for a process if ksm has been enabled for the process.

6) add new prctl option to get and set ksm for a process

This adds two new options to the prctl system call
- enable ksm for all vmas of a process (if the vmas support it).
- query if ksm has been enabled for a process.

3. Disabling MMF_VM_MERGE_ANY for storage keys in s390

In the s390 architecture when storage keys are used, the MMF_VM_MERGE_ANY will be disabled.

---
 arch/s390/mm/gmap.c            |   1 +
 include/linux/ksm.h            |  31 +++++++--
 include/linux/sched/coredump.h |   1 +
 include/uapi/linux/prctl.h     |   2 +
 kernel/fork.c                  |   1 +
 kernel/sys.c                   |  24 +++++++
 mm/ksm.c                       | 111 ++++++++++++++++++++++++++-------
 mm/mmap.c                      |   7 +++
 8 files changed, 151 insertions(+), 27 deletions(-)

index 5a716bdcba05..9d85e5589474 100644
@@ -2591,6 +2591,7 @@ int gmap_mark_unmergeable(void)
 	int ret;
 	VMA_ITERATOR(vmi, mm, 0);
 
+	clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
 	for_each_vma(vmi, vma) {
 		/* Copy vm_flags to avoid partial modifications in ksm_madvise */
 		vm_flags = vma->vm_flags;

index 7e232ba59b86..c65455bf124c 100644
@@ -18,20 +18,29 @@
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags);
-int __ksm_enter(struct mm_struct *mm);
-void __ksm_exit(struct mm_struct *mm);
+
+int ksm_add_mm(struct mm_struct *mm);
+void ksm_add_vma(struct vm_area_struct *vma);
+void ksm_add_vmas(struct mm_struct *mm);
+
+int __ksm_enter(struct mm_struct *mm, int flag);
+void __ksm_exit(struct mm_struct *mm, int flag);
 
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
+	if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
+		return ksm_add_mm(mm);
 	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
-		return __ksm_enter(mm);
+		return __ksm_enter(mm, MMF_VM_MERGEABLE);
 	return 0;
 }
 
 static inline void ksm_exit(struct mm_struct *mm)
 {
-	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
-		__ksm_exit(mm);
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGE_ANY);
+	else if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGEABLE);
 }
 
 /*

@@ -53,6 +62,18 @@ void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
 
 #else  /* !CONFIG_KSM */
 
+static inline int ksm_add_mm(struct mm_struct *mm)
+{
+}
+
+static inline void ksm_add_vma(struct vm_area_struct *vma)
+{
+}
+
+static inline void ksm_add_vmas(struct mm_struct *mm)
+{
+}
+
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
 	return 0;

index 0e17ae7fbfd3..0ee96ea7a0e9 100644
@@ -90,4 +90,5 @@ static inline int get_dumpable(struct mm_struct *mm)
 #define MMF_INIT_MASK		(MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
 				 MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK)
 
+#define MMF_VM_MERGE_ANY	29
 #endif /* _LINUX_SCHED_COREDUMP_H */

index 1312a137f7fb..759b3f53e53f 100644
@@ -290,4 +290,6 @@ struct prctl_mm_map {
 #define PR_SET_VMA		0x53564d41
 # define PR_SET_VMA_ANON_NAME		0
 
+#define PR_SET_MEMORY_MERGE		67
+#define PR_GET_MEMORY_MERGE		68
 #endif /* _LINUX_PRCTL_H */

index f68954d05e89..1520697cf6c7 100644
@@ -686,6 +686,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 		if (vma_iter_bulk_store(&vmi, tmp))
 			goto fail_nomem_vmi_store;
 
+		ksm_add_vma(tmp);
 		mm->map_count++;
 		if (!(tmp->vm_flags & VM_WIPEONFORK))
 			retval = copy_page_range(tmp, mpnt);

index 495cd87d9bf4..3e6918a10259 100644
@@ -15,6 +15,7 @@
 #include <linux/highuid.h>
 #include <linux/fs.h>
 #include <linux/kmod.h>
+#include <linux/ksm.h>
 #include <linux/perf_event.h>
 #include <linux/resource.h>
 #include <linux/kernel.h>

@@ -2661,6 +2662,29 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	case PR_SET_VMA:
 		error = prctl_set_vma(arg2, arg3, arg4, arg5);
 		break;
+#ifdef CONFIG_KSM
+	case PR_SET_MEMORY_MERGE:
+		if (mmap_write_lock_killable(me->mm))
+			return -EINTR;
+
+		if (arg2) {
+			int err = ksm_add_mm(me->mm);
+			if (err)
+				return err;
+
+			ksm_add_vmas(me->mm);
+		} else {
+			clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
+		}
+		mmap_write_unlock(me->mm);
+		break;
+	case PR_GET_MEMORY_MERGE:
+		if (arg2 || arg3 || arg4 || arg5)
+			return -EINVAL;
+
+		error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
+		break;
+#endif
 	default:
 		error = -EINVAL;
 		break;

index 740b54be3ed4..483e182e0b9d 100644
@@ -46,6 +46,7 @@
 #include <linux/pkeys.h>
 #include <linux/oom.h>
 #include <linux/sched/mm.h>
+#include <linux/ksm.h>
 
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>

@@ -2213,6 +2214,8 @@ int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	/* vma_complete stores the new vma */
 	vma_complete(&vp, vmi, vma->vm_mm);
 
+	ksm_add_vma(new);
+
 	/* Success. */
 	if (new_below)
 		vma_next(vmi);

@@ -2664,6 +2667,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	if (file && vm_flags & VM_SHARED)
 		mapping_unmap_writable(file->f_mapping);
 	file = vma->vm_file;
+	ksm_add_vma(vma);
 expanded:
 	perf_event_mmap(vma);
 

@@ -2936,6 +2940,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		goto mas_store_fail;
 
 	mm->map_count++;
+	ksm_add_vma(vma);
 out:
 	perf_event_mmap(vma);
 	mm->total_vm += len >> PAGE_SHIFT;

@@ -3180,6 +3185,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 		if (vma_link(mm, new_vma))
 			goto out_vma_link;
 		*need_rmap_locks = false;
+		ksm_add_vma(new_vma);
 	}
 	validate_mm_mt(mm);
 	return new_vma;

@@ -3356,6 +3362,7 @@ static struct vm_area_struct *__install_special_mapping(
 	vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
 
 	perf_event_mmap(vma);
+	ksm_add_vma(vma);
 
 	validate_mm_mt(mm);
 	return vma;

2.34.1

ksm_add_mm() and ksm_add_vmas() is not needed. However ksm_add_vma() is required. It is called from mm/mmap.c

Thanks for catching this, I'll fix it in the next version.

This adds the general_profit KSM sysfs knob and the process profit metric and process merge type knobs to ksm_stat.

1) expose general_profit metric

The documentation mentions a general profit metric, however this metric is not calculated. In addition the formula depends on the size of internal structures, which makes it more difficult for an administrator to make the calculation. Adding the metric for a better user experience.

2) document general_profit sysfs knob

3) calculate ksm process profit metric

The ksm documentation mentions the process profit metric and how to calculate it. This adds the calculation of the metric.

4) add ksm_merge_type() function

This adds the ksm_merge_type function. The function returns the merge type for the process. For madvise it returns "madvise", for prctl it returns "process" and otherwise it returns "none".

5) mm: expose ksm process profit metric and merge type in ksm_stat

This exposes the ksm process profit metric in /proc/<pid>/ksm_stat. The name of the value is ksm_merge_type. The documentation mentions the formula for the ksm process profit metric, however it does not calculate it. In addition the formula depends on the size of internal structures. So it makes sense to expose it.

6) document new procfs ksm knobs

---
 Documentation/ABI/testing/sysfs-kernel-mm-ksm |  8 +++++
 Documentation/admin-guide/mm/ksm.rst          |  8 ++++-
 fs/proc/base.c                                |  5 +++
 include/linux/ksm.h                           |  5 +++
 mm/ksm.c                                      | 32 +++++++++++++++++++
 5 files changed, 57 insertions(+), 1 deletion(-)

index d244674a9480..7768e90f7a8f 100644
@@ -51,3 +51,11 @@ Description:	Control merging pages across different NUMA nodes.
 
 		When it is set to 0 only pages from the same node are merged,
 		otherwise pages from all nodes can be merged together (default).
+
+What:		/sys/kernel/mm/ksm/general_profit
+Date:		January 2023
+KernelVersion:  6.1
+Contact:	Linux memory management mailing list <[email protected]>
+Description:	Measure how effective KSM is.
+		general_profit: how effective is KSM. The formula for the
+		calculation is in Documentation/admin-guide/mm/ksm.rst.

index 270560fef3b2..d2929964cd0f 100644
@@ -157,6 +157,8 @@ stable_node_chains_prune_millisecs
 
 The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
+general_profit
+        how effective is KSM. The calculation is explained below.
 pages_shared
         how many shared pages are being used
 pages_sharing

@@ -214,7 +216,8 @@ several times, which are unprofitable memory consumed.
 			  ksm_rmap_items * sizeof(rmap_item).
 
    where ksm_merging_pages is shown under the directory ``/proc/<pid>/``,
-   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``.
+   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``. The process profit
+   is also shown in ``/proc/<pid>/ksm_stat`` as ksm_process_profit.
 
 From the perspective of application, a high ratio of ``ksm_rmap_items`` to
 ``ksm_merging_pages`` means a bad madvise-applied policy, so developers or

@@ -225,6 +228,9 @@ so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU
 or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped,
 because the ksm profit is approximately zero or negative.
 
+The ksm_merge_type in ``/proc/<pid>/ksm_stat`` shows the merge type of the
+process. Valid values are ``none``, ``madvise`` and ``process``.
+
 Monitoring KSM events
 =====================
 

index 07463ad4a70a..c74450318e05 100644
@@ -96,6 +96,7 @@
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
 #include <linux/cn_proc.h>
+#include <linux/ksm.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"

@@ -3199,6 +3200,7 @@ static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace *
 
 	return 0;
 }
+
 static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
 				struct pid *pid, struct task_struct *task)
 {

@@ -3208,6 +3210,9 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
 	if (mm) {
 		seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items);
 		seq_printf(m, "zero_pages_sharing %lu\n", mm->ksm_zero_pages_sharing);
+		seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
+		seq_printf(m, "ksm_merge_type %s\n", ksm_merge_type(mm));
+		seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
 		mmput(mm);
 	}
 

index c65455bf124c..4c32f9bca723 100644
@@ -60,6 +60,11 @@ struct page *ksm_might_need_to_copy(struct page *page,
 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
 
+#ifdef CONFIG_PROC_FS
+long ksm_process_profit(struct mm_struct *);
+const char *ksm_merge_type(struct mm_struct *mm);
+#endif /* CONFIG_PROC_FS */
+
 #else  /* !CONFIG_KSM */
 
 static inline int ksm_add_mm(struct mm_struct *mm)

index ab95ae0f9def..76b10ff840ac 100644
@@ -3042,6 +3042,25 @@ static void wait_while_offlining(void)
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
+#ifdef CONFIG_PROC_FS
+long ksm_process_profit(struct mm_struct *mm)
+{
+	return (long)mm->ksm_merging_pages * PAGE_SIZE -
+		mm->ksm_rmap_items * sizeof(struct ksm_rmap_item);
+}
+
+/* Return merge type name as string. */
+const char *ksm_merge_type(struct mm_struct *mm)
+{
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		return "process";
+	else if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		return "madvise";
+	else
+		return "none";
+}
+#endif /* CONFIG_PROC_FS */
+
 #ifdef CONFIG_SYSFS
 /*
  * This all compiles without CONFIG_SYSFS, but is a waste of space.

@@ -3313,6 +3332,18 @@ static ssize_t zero_pages_sharing_show(struct kobject *kobj,
 }
 KSM_ATTR_RO(zero_pages_sharing);
 
+static ssize_t general_profit_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	long general_profit;
+
+	general_profit = ksm_pages_sharing * PAGE_SIZE -
+				ksm_rmap_items * sizeof(struct ksm_rmap_item);
+
+	return sysfs_emit(buf, "%ld\n", general_profit);
+}
+KSM_ATTR_RO(general_profit);
+
 static ssize_t stable_node_dups_show(struct kobject *kobj,
 				     struct kobj_attribute *attr, char *buf)
 {

@@ -3378,6 +3409,7 @@ static struct attribute *ksm_attrs[] = {
 	&stable_node_dups_attr.attr,
 	&stable_node_chains_prune_millisecs_attr.attr,
 	&use_zero_pages_attr.attr,
+	&general_profit_attr.attr,
 	NULL,
 };
 

2.34.1

I'm curious, why exactly is this change required in this context? It might be sufficient to observe if the prctl is set for a process. If not, the ksm stats can reveal whether KSM is still active for that process -> madvise.

For your use case, I'd assume it's pretty unnecessary to expose that.

If there is no compelling reason, I'd suggest to drop this and limit this patch to exposing the general/per-mm profit, which I can understand why it's desirable when fine-tuning a workload.

[...]

Thanks,

David / dhildenb

In the next version, the ksm_merge_type function() is removed.

Updated in the next version.

Updated in the next version.

Fixed in the next version.

Removed the cast in the next version.

This adds three new tests to the selftests for KSM. These tests use the new prctl API's to enable and disable KSM.

1) add new prctl flags to prctl header file in tools dir

This adds the new prctl flags to the include file prct.h in the tools directory. This makes sure they are available for testing.

2) add KSM prctl merge test

This adds the -t option to the ksm_tests program. The -t flag allows to specify if it should use madvise or prctl ksm merging.

3) add KSM get merge type test

This adds the -G flag to the ksm_tests program to query the KSM status with prctl after KSM has been enabled with prctl.

4) add KSM fork test

Add fork test to verify that the MMF_VM_MERGE_ANY flag is inherited by the child process.

5) add two functions for debugging merge outcome

This adds two functions to report the metrics in /proc/self/ksm_stat and /sys/kernel/debug/mm/ksm.

The debugging can be enabled with the following command line:
make -C tools/testing/selftests TARGETS="mm" --keep-going \
EXTRA_CFLAGS=-DDEBUG=1

---
 tools/include/uapi/linux/prctl.h       |   2 +
 tools/testing/selftests/mm/Makefile    |   2 +-
 tools/testing/selftests/mm/ksm_tests.c | 254 +++++++++++++++++++++----
 3 files changed, 218 insertions(+), 40 deletions(-)

index a5e06dcbba13..e4c629c1f1b0 100644
@@ -284,4 +284,6 @@ struct prctl_mm_map {
 #define PR_SET_VMA		0x53564d41
 # define PR_SET_VMA_ANON_NAME		0
 
+#define PR_SET_MEMORY_MERGE		67
+#define PR_GET_MEMORY_MERGE		68
 #endif /* _LINUX_PRCTL_H */

index c31d952cff68..fbf5646b1072 100644
@@ -29,7 +29,7 @@ MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/' -e 's/ppc64.*/p
 # LDLIBS.
 MAKEFLAGS += --no-builtin-rules
 
-CFLAGS = -Wall -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
+CFLAGS = -Wall -I $(top_srcdir) -I $(top_srcdir)/tools/include/uapi $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
 LDLIBS = -lrt -lpthread
 TEST_GEN_FILES = cow
 TEST_GEN_FILES += compaction_test

2.34.1