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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 20 Jun 2024 12:53:06 +0200
Subject: [PATCH 3/3] zram: Shrink zram_table_entry::flags.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz
The zram_table_entry::flags member is of type long and uses 8 bytes on a
64bit architecture. With a PAGE_SIZE of 256KiB we have PAGE_SHIFT of 18
which in turn leads to __NR_ZRAM_PAGEFLAGS = 27. This still fits in an
ordinary integer.
By reducing it the size of `flags' to four bytes, the size of the struct
goes back to 16 bytes. The padding between the lock and ac_time (if
enabled) is also gone.
Make zram_table_entry::flags an unsigned int and update the build test
to reflect the change.
Link: https://lore.kernel.org/r/20240620153556.777272-4-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/block/zram/zram_drv.c | 3 ++-
drivers/block/zram/zram_drv.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2412,9 +2412,10 @@ static void destroy_devices(void)
static int __init zram_init(void)
{
+ struct zram_table_entry zram_te;
int ret;
- BUILD_BUG_ON(__NR_ZRAM_PAGEFLAGS > BITS_PER_LONG);
+ BUILD_BUG_ON(__NR_ZRAM_PAGEFLAGS > sizeof(zram_te.flags) * 8);
ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare",
zcomp_cpu_up_prepare, zcomp_cpu_dead);
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -66,7 +66,7 @@ struct zram_table_entry {
unsigned long handle;
unsigned long element;
};
- unsigned long flags;
+ unsigned int flags;
spinlock_t lock;
#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
ktime_t ac_time;
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