From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2FA65275AFD; Wed, 9 Sep 2026 13:48:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788961701; cv=none; b=H1f8o2Ki9CcA1GpTxZbaNqxvAWpKsbRfVhRRjBsqOyGwCdlDspQqtOrhrXMU5H6aAmKpfAKt10t7oD/CPVutdec07LIRNzZpkzy2Upfig++r+IcnrhEyHMVtsdUZTW/l3esytJVAzsZkX4RCHPlw/nIdqpP1y9iBHCtun3kJSlw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788961701; c=relaxed/simple; bh=bacqDqUiL9MabGAZ5LddywZBfJUaQccfBJlh51cQoLQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fhrjp1bnay6V647fOiLOWJI1MH5d0KyqU1rvsTuaFJZDgTE5E4FxME3uckbPx2TnIOYUiUyRfriy4e9kQq4luJomGTXCuUbdxohDkECovVx4up5NVpF/ESZbHAqWfWv/Bk5nv+wwmyNuD4Mqc++qWm2s41BfUMNTeEUOhun26sI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BMKm1UbK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BMKm1UbK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 750211F00A3A; Wed, 9 Sep 2026 13:48:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788961700; bh=YJXyqa/3//9ypWbDr4qXVO7AwIjL8CN8vLWsJvl9tOE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BMKm1UbKcYevPqTi5uUbSX2nwSfh+0EJs/xL0CTKMozVpxCE7eXXNoi7h236jTps/ t7RA6FxLR2kyy56OXDXCZYQW5kMKCzZVRTRoryGTTOlqtLbl8g2Uyg2hVqWly+hp1W GdqbT2K3bA88YSgjjZrotoG8eAt6/gn1M46CSt6w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Carlier , Sergey Senozhatsky , Minchan Kim , Andrew Morton , Sasha Levin Subject: [PATCH 7.2 008/556] zram: fix slot lock bit position on big-endian 64-bit Date: Wed, 9 Sep 2026 15:34:48 +0200 Message-ID: <20260909134230.756962550@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134230.441546314@linuxfoundation.org> References: <20260909134230.441546314@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Carlier [ Upstream commit a8b5875741d416703e19ad8eeac6fce8a12bd6e4 ] 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/20260810202241.2436603-1-devnexen@gmail.com Fixes: 2e8ff2f51dde ("zram: use u32 for entry ac_time tracking") Signed-off-by: David Carlier Reviewed-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/block/zram/zram_drv.c | 6 +++--- drivers/block/zram/zram_drv.h | 14 ++++++++++++++ 2 files changed, 17 insertions(+), 3 deletions(-) --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -81,7 +81,7 @@ static __must_check bool slot_trylock(st { 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, 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 *zra 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) --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -15,6 +15,7 @@ #ifndef _ZRAM_DRV_H_ #define _ZRAM_DRV_H_ +#include #include #include @@ -58,6 +59,19 @@ enum 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 * locking primitives (e.g. mutex) will significantly increase sizeof()