FAILED: patch "[PATCH] zram: fix slot lock bit position on big-endian 64-bit" failed to apply to 7.2-stable tree

PATCH New [email protected] 2 participants 3 messages Sep 3 – Sep 4

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author maintainer

2026-09-03 13:06 UTC #0 lore raw

The patch below does not apply to the 7.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.2.y
git checkout FETCH_HEAD
git cherry-pick -x a8b5875741d416703e19ad8eeac6fce8a12bd6e4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090337-onshore-thermos-9127@gregkh' --subject-prefix 'PATCH 7.2.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a8b5875741d416703e19ad8eeac6fce8a12bd6e4 Mon Sep 17 00:00:00 2001
From: David Carlier <[email protected]>
Date: Mon, 10 Aug 2026 21:22:37 +0100
Subject: [PATCH] zram: fix slot lock bit position on big-endian 64-bit

The slot lock is a bit operation on the whole __lock word, which flags and ac_time alias as two u32s. On little-endian the lock bit lands in the position ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out. On 64-bit big-endian it lands in ac_time instead: with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from mark_slot_accessed() or slot_free() wipes out the held lock bit, letting another CPU take the same slot lock; an access time value with that bit set makes the slot look locked forever.

Shift the lock bit into the flags half of the word on big-endian 64-bit.

Link https://lore.kernel.org/[email protected] open here

Fixes 2e8ff2f51dde ("zram: use u32 for entry ac_time tracking")

Signed-off-by David Carlier <[email protected]>

Reviewed-by Sergey Senozhatsky <[email protected]>

Cc Minchan Kim <[email protected]>

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

drivers/block/zram/zram_drv.c +3 -3

index d09fdca49cbd..a9b3bb1d3bef 100644
@@ -74,7 +74,7 @@ static __must_check bool slot_trylock(struct zram *zram, unsigned long index)
 {
 	unsigned long *lock = &zram->table[index].__lock;
 
-	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK, lock)) {
+	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK_BIT, lock)) {
 		mutex_acquire(&zram->table_lock_map, 0, 1, _RET_IP_);
 		lock_acquired(&zram->table_lock_map, _RET_IP_);
 		return true;

@@ -88,7 +88,7 @@ static void slot_lock(struct zram *zram, unsigned long index)
 	unsigned long *lock = &zram->table[index].__lock;
 
 	mutex_acquire(&zram->table_lock_map, 0, 0, _RET_IP_);
-	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK, TASK_UNINTERRUPTIBLE);
+	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK_BIT, TASK_UNINTERRUPTIBLE);
 	lock_acquired(&zram->table_lock_map, _RET_IP_);
 }

@@ -97,7 +97,7 @@ static void slot_unlock(struct zram *zram, unsigned long index)
 	unsigned long *lock = &zram->table[index].__lock;
 
 	mutex_release(&zram->table_lock_map, _RET_IP_);
-	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK, lock);
+	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK_BIT, lock);
 }
 
 static inline bool init_done(struct zram *zram)

drivers/block/zram/zram_drv.h +14 -0

index 4fddc582f3b8..7a55d751417e 100644
@@ -15,6 +15,7 @@
 #ifndef _ZRAM_DRV_H_
 #define _ZRAM_DRV_H_
 
+#include <asm/byteorder.h>
 #include <linux/rwsem.h>
 #include <linux/zsmalloc.h>

@@ -57,6 +58,19 @@ enum zram_pageflags {
 	__NR_ZRAM_PAGEFLAGS,
 };
 
+/*
+ * The slot lock is a bit-wait lock on the whole __lock word, while
+ * flags and ac_time alias that word as two u32s.  The lock bit must
+ * land in the slot that ZRAM_ENTRY_LOCK reserves in attr.flags; on
+ * 64-bit big-endian the flags word maps to the upper half of __lock,
+ * so the bit position has to be shifted up.
+ */
+#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
+#define ZRAM_ENTRY_LOCK_BIT  (ZRAM_ENTRY_LOCK + 32)
+#else
+#define ZRAM_ENTRY_LOCK_BIT  ZRAM_ENTRY_LOCK
+#endif
+
 /*
  * Allocated for each disk page.  We use bit-lock (ZRAM_ENTRY_LOCK bit
  * of flags) to save memory.  There can be plenty of entries and standard

Sasha Levin

maintainer

2026-09-04 18:49 UTC #1 lore raw

PATCH 1/2 zram: move lockmap to be per-zram instead per table

From: Sebastian Andrzej Siewior <[email protected]>

[ Upstream commit dbb7ba9c7fa81a48ed2a108ad684cf3655f3ae4b ]

Patch series "zram: lockmap tweaks".

This patch (of 2):

The zram object contains an array zram_table_entry. Each one has a `lock' variable and each has a matching struct lockdep_map. This mimics a struct mutex.

It uses always the same key for all lockdep_map instances. This makes it look like the same lock to lockdep. Therefore it could be reduced to have one lockdep_map per struct zram.

Use only one struct lockdep_map per struct zram.

Link https://lore.kernel.org/[email protected] open here

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Reviewed-by Sergey Senozhatsky <[email protected]>

Tested-by Sergey Senozhatsky <[email protected]>

Cc Jens Axboe <[email protected]>

Cc Minchan Kim <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Stable-dep-of: a8b5875741d4 ("zram: fix slot lock bit position on big-endian 64-bit")

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/block/zram/zram_drv.c | 21 +++++++++------------
 drivers/block/zram/zram_drv.h |  2 +-
 2 files changed, 10 insertions(+), 13 deletions(-)

drivers/block/zram/zram_drv.c +9 ~~-12~~

index ace65c586072b..4223002d80b41 100644
@@ -57,14 +57,12 @@ static size_t huge_class_size;
 static const struct block_device_operations zram_devops;
 
 static void slot_free(struct zram *zram, u32 index);
-#define slot_dep_map(zram, index) (&(zram)->table[(index)].dep_map)
 
-static void slot_lock_init(struct zram *zram, u32 index)
+static void slot_lock_init(struct zram *zram)
 {
 	static struct lock_class_key __key;
 
-	lockdep_init_map(slot_dep_map(zram, index), "zram->table[index].lock",
-			 &__key, 0);
+	lockdep_init_map(&zram->table_lock_map, "zram->table[index].lock", &__key, 0);
 }
 
 /*

@@ -84,8 +82,8 @@ static __must_check bool slot_trylock(struct zram *zram, u32 index)
 	unsigned long *lock = &zram->table[index].__lock;
 
 	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK, lock)) {
-		mutex_acquire(slot_dep_map(zram, index), 0, 1, _RET_IP_);
-		lock_acquired(slot_dep_map(zram, index), _RET_IP_);
+		mutex_acquire(&zram->table_lock_map, 0, 1, _RET_IP_);
+		lock_acquired(&zram->table_lock_map, _RET_IP_);
 		return true;
 	}

@@ -96,16 +94,16 @@ static void slot_lock(struct zram *zram, u32 index)
 {
 	unsigned long *lock = &zram->table[index].__lock;
 
-	mutex_acquire(slot_dep_map(zram, index), 0, 0, _RET_IP_);
+	mutex_acquire(&zram->table_lock_map, 0, 0, _RET_IP_);
 	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK, TASK_UNINTERRUPTIBLE);
-	lock_acquired(slot_dep_map(zram, index), _RET_IP_);
+	lock_acquired(&zram->table_lock_map, _RET_IP_);
 }
 
 static void slot_unlock(struct zram *zram, u32 index)
 {
 	unsigned long *lock = &zram->table[index].__lock;
 
-	mutex_release(slot_dep_map(zram, index), _RET_IP_);
+	mutex_release(&zram->table_lock_map, _RET_IP_);
 	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK, lock);
 }

@@ -1984,7 +1982,7 @@ static void zram_meta_free(struct zram *zram, u64 disksize)
 
 static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 {
-	size_t num_pages, index;
+	size_t num_pages;
 
 	num_pages = disksize >> PAGE_SHIFT;
 	zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table)));

@@ -2001,8 +1999,7 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 	if (!huge_class_size)
 		huge_class_size = zs_huge_class_size(zram->mem_pool);
 
-	for (index = 0; index < num_pages; index++)
-		slot_lock_init(zram, index);
+	slot_lock_init(zram);
 
 	return true;
 }

drivers/block/zram/zram_drv.h +1 -1

index 08d1774c15db6..8290dc6e23352 100644
@@ -74,7 +74,6 @@ struct zram_table_entry {
 #endif
 		} attr;
 	};
-	struct lockdep_map dep_map;
 };
 
 struct zram_stats {

@@ -107,6 +106,7 @@ struct zram_stats {
 
 struct zram {
 	struct zram_table_entry *table;
+	struct lockdep_map table_lock_map;
 	struct zs_pool *mem_pool;
 	struct zcomp *comps[ZRAM_MAX_COMPS];
 	struct zcomp_params params[ZRAM_MAX_COMPS];

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-04 18:49 UTC #2 lore raw

PATCH 2/2 zram: fix slot lock bit position on big-endian 64-bit

From: David Carlier <[email protected]>

[ Upstream commit a8b5875741d416703e19ad8eeac6fce8a12bd6e4 ]

Shift the lock bit into the flags half of the word on big-endian 64-bit.

Link https://lore.kernel.org/[email protected] open here

Fixes 2e8ff2f51dde ("zram: use u32 for entry ac_time tracking")

Signed-off-by David Carlier <[email protected]>

Reviewed-by Sergey Senozhatsky <[email protected]>

Cc Minchan Kim <[email protected]>

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/block/zram/zram_drv.c |  6 +++---
 drivers/block/zram/zram_drv.h | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

drivers/block/zram/zram_drv.c +3 -3

index 4223002d80b41..be8308c26fb06 100644
@@ -81,7 +81,7 @@ static __must_check bool slot_trylock(struct zram *zram, u32 index)
 {
 	unsigned long *lock = &zram->table[index].__lock;
 
-	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK, lock)) {
+	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK_BIT, lock)) {
 		mutex_acquire(&zram->table_lock_map, 0, 1, _RET_IP_);
 		lock_acquired(&zram->table_lock_map, _RET_IP_);
 		return true;

@@ -95,7 +95,7 @@ static void slot_lock(struct zram *zram, u32 index)
 	unsigned long *lock = &zram->table[index].__lock;
 
 	mutex_acquire(&zram->table_lock_map, 0, 0, _RET_IP_);
-	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK, TASK_UNINTERRUPTIBLE);
+	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK_BIT, TASK_UNINTERRUPTIBLE);
 	lock_acquired(&zram->table_lock_map, _RET_IP_);
 }

@@ -104,7 +104,7 @@ static void slot_unlock(struct zram *zram, u32 index)
 	unsigned long *lock = &zram->table[index].__lock;
 
 	mutex_release(&zram->table_lock_map, _RET_IP_);
-	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK, lock);
+	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK_BIT, lock);
 }
 
 static inline bool init_done(struct zram *zram)

drivers/block/zram/zram_drv.h +14 -0

index 8290dc6e23352..996bb99ea8bbf 100644
@@ -15,6 +15,7 @@
 #ifndef _ZRAM_DRV_H_
 #define _ZRAM_DRV_H_
 
+#include <asm/byteorder.h>
 #include <linux/rwsem.h>
 #include <linux/zsmalloc.h>

@@ -57,6 +58,19 @@ enum zram_pageflags {
 	__NR_ZRAM_PAGEFLAGS,
 };
 
+/*
+ * The slot lock is a bit-wait lock on the whole __lock word, while
+ * flags and ac_time alias that word as two u32s.  The lock bit must
+ * land in the slot that ZRAM_ENTRY_LOCK reserves in attr.flags; on
+ * 64-bit big-endian the flags word maps to the upper half of __lock,
+ * so the bit position has to be shifted up.
+ */
+#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
+#define ZRAM_ENTRY_LOCK_BIT  (ZRAM_ENTRY_LOCK + 32)
+#else
+#define ZRAM_ENTRY_LOCK_BIT  ZRAM_ENTRY_LOCK
+#endif
+
 /*
  * Allocated for each disk page.  We use bit-lock (ZRAM_ENTRY_LOCK bit
  * of flags) to save memory.  There can be plenty of entries and standard

Signature · 1 line

2.53.0