zram: split memory-tracking and ac-time tracking

ZRAM_MEMORY_TRACKING enables two features:
- per-entry ac-time tracking
- debugfs interface

The latter one is the reason why memory-tracking depends on DEBUG_FS,
while the former one is used far beyond debugging these days.  Namely
ac-time is used for fine grained writeback of idle entries (pages).

Move ac-time tracking under its own config option so that it can be
enabled (along with writeback) on systems without DEBUG_FS.

[senozhatsky@chromium.org: ifdef fixup, per Dmytro]
  Link: https://lkml.kernel.org/r/20231117013543.540280-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20231115024223.4133148-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dmytro Maluka <dmaluka@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 24 insertions, 16 deletions

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 0386b7da02aa..af201392ed52 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -69,9 +69,18 @@ config ZRAM_WRITEBACK
 
 	 See Documentation/admin-guide/blockdev/zram.rst for more information.
 
+config ZRAM_TRACK_ENTRY_ACTIME
+	bool "Track access time of zram entries"
+	depends on ZRAM
+	help
+	  With this feature zram tracks access time of every stored
+	  entry (page), which can be used for a more fine grained IDLE
+	  pages writeback.
+
 config ZRAM_MEMORY_TRACKING
 	bool "Track zRam block status"
 	depends on ZRAM && DEBUG_FS
+	select ZRAM_TRACK_ENTRY_ACTIME
 	help
 	  With this feature, admin can track the state of allocated blocks
 	  of zRAM. Admin could see the information via
@@ -86,4 +95,4 @@ config ZRAM_MULTI_COMP
 	  This will enable multi-compression streams, so that ZRAM can
 	  re-compress pages using a potentially slower but more effective
 	  compression algorithm. Note, that IDLE page recompression
-	  requires ZRAM_MEMORY_TRACKING.
+	  requires ZRAM_TRACK_ENTRY_ACTIME.
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d77d3664ca08..f6b286e7f310 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -174,6 +174,14 @@ static inline u32 zram_get_priority(struct zram *zram, u32 index)
 	return prio & ZRAM_COMP_PRIORITY_MASK;
 }
 
+static void zram_accessed(struct zram *zram, u32 index)
+{
+	zram_clear_flag(zram, index, ZRAM_IDLE);
+#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
+	zram->table[index].ac_time = ktime_get_boottime();
+#endif
+}
+
 static inline void update_used_max(struct zram *zram,
 					const unsigned long pages)
 {
@@ -293,8 +301,9 @@ static void mark_idle(struct zram *zram, ktime_t cutoff)
 		zram_slot_lock(zram, index);
 		if (zram_allocated(zram, index) &&
 				!zram_test_flag(zram, index, ZRAM_UNDER_WB)) {
-#ifdef CONFIG_ZRAM_MEMORY_TRACKING
-			is_idle = !cutoff || ktime_after(cutoff, zram->table[index].ac_time);
+#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
+			is_idle = !cutoff || ktime_after(cutoff,
+							 zram->table[index].ac_time);
 #endif
 			if (is_idle)
 				zram_set_flag(zram, index, ZRAM_IDLE);
@@ -317,7 +326,7 @@ static ssize_t idle_store(struct device *dev,
 		 */
 		u64 age_sec;
 
-		if (IS_ENABLED(CONFIG_ZRAM_MEMORY_TRACKING) && !kstrtoull(buf, 0, &age_sec))
+		if (IS_ENABLED(CONFIG_ZRAM_TRACK_ENTRY_ACTIME) && !kstrtoull(buf, 0, &age_sec))
 			cutoff_time = ktime_sub(ktime_get_boottime(),
 					ns_to_ktime(age_sec * NSEC_PER_SEC));
 		else
@@ -841,12 +850,6 @@ static void zram_debugfs_destroy(void)
 	debugfs_remove_recursive(zram_debugfs_root);
 }
 
-static void zram_accessed(struct zram *zram, u32 index)
-{
-	zram_clear_flag(zram, index, ZRAM_IDLE);
-	zram->table[index].ac_time = ktime_get_boottime();
-}
-
 static ssize_t read_block_state(struct file *file, char __user *buf,
 				size_t count, loff_t *ppos)
 {
@@ -930,10 +933,6 @@ static void zram_debugfs_unregister(struct zram *zram)
 #else
 static void zram_debugfs_create(void) {};
 static void zram_debugfs_destroy(void) {};
-static void zram_accessed(struct zram *zram, u32 index)
-{
-	zram_clear_flag(zram, index, ZRAM_IDLE);
-};
 static void zram_debugfs_register(struct zram *zram) {};
 static void zram_debugfs_unregister(struct zram *zram) {};
 #endif
@@ -1254,7 +1253,7 @@ static void zram_free_page(struct zram *zram, size_t index)
 {
 	unsigned long handle;
 
-#ifdef CONFIG_ZRAM_MEMORY_TRACKING
+#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
 	zram->table[index].ac_time = 0;
 #endif
 	if (zram_test_flag(zram, index, ZRAM_IDLE))
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index d090753f97be..3b94d12f41b4 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -69,7 +69,7 @@ struct zram_table_entry {
 		unsigned long element;
 	};
 	unsigned long flags;
-#ifdef CONFIG_ZRAM_MEMORY_TRACKING
+#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
 	ktime_t ac_time;
 #endif
 };