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Subject[PATCH v3 10/10] zram: use atomic64_xxx() to replace zram_stat64_xxx()
Date
Use atomic64_xxx() to replace open-coded zram_stat64_xxx().
Some architectures have native support of atomic64 operations,
so we can get rid of the spin_lock() in zram_stat64_xxx().
On the other hand, for platforms use generic version of atomic64
implement, it may cause an extra save/restore of the interrupt
flag. So it's a tradeoff.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
drivers/staging/zram/zram_drv.c | 37 ++++++++-----------------------------
drivers/staging/zram/zram_drv.h | 19 +++++++++++--------
drivers/staging/zram/zram_sysfs.c | 21 +++++----------------
3 files changed, 24 insertions(+), 53 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index b4f84b6b..518e87d 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -42,25 +42,6 @@ static struct zram *zram_devices;
/* Module params (documentation at end) */
static unsigned int num_devices = 1;

-static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
-{
- spin_lock(&zram->stat64_lock);
- *v = *v + inc;
- spin_unlock(&zram->stat64_lock);
-}
-
-static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
-{
- spin_lock(&zram->stat64_lock);
- *v = *v - dec;
- spin_unlock(&zram->stat64_lock);
-}
-
-static void zram_stat64_inc(struct zram *zram, u64 *v)
-{
- zram_stat64_add(zram, v, 1);
-}
-
static int zram_test_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
{
@@ -120,8 +101,7 @@ static void zram_free_page(struct zram *zram, size_t index)
if (size <= PAGE_SIZE / 2)
zram->stats.good_compress--;

- zram_stat64_sub(zram, &zram->stats.compr_size,
- meta->table[index].size);
+ atomic64_sub(meta->table[index].size, &zram->stats.compr_size);
zram->stats.pages_stored--;

meta->table[index].handle = 0;
@@ -172,7 +152,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
/* Should NEVER happen. Return bio error if it does. */
if (unlikely(ret != LZO_E_OK)) {
pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
- zram_stat64_inc(zram, &zram->stats.failed_reads);
+ atomic64_inc(&zram->stats.failed_reads);
return ret;
}

@@ -326,7 +306,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
meta->table[index].size = clen;

/* Update stats */
- zram_stat64_add(zram, &zram->stats.compr_size, clen);
+ atomic64_add(clen, &zram->stats.compr_size);
zram->stats.pages_stored++;
if (clen <= PAGE_SIZE / 2)
zram->stats.good_compress++;
@@ -336,7 +316,7 @@ out:
kfree(uncmem);

if (ret)
- zram_stat64_inc(zram, &zram->stats.failed_writes);
+ atomic64_inc(&zram->stats.failed_writes);
return ret;
}

@@ -373,10 +353,10 @@ static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)

switch (rw) {
case READ:
- zram_stat64_inc(zram, &zram->stats.num_reads);
+ atomic64_inc(&zram->stats.num_reads);
break;
case WRITE:
- zram_stat64_inc(zram, &zram->stats.num_writes);
+ atomic64_inc(&zram->stats.num_writes);
break;
}

@@ -456,7 +436,7 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio)
goto error;

if (!valid_io_request(zram, bio)) {
- zram_stat64_inc(zram, &zram->stats.invalid_io);
+ atomic64_inc(&zram->stats.invalid_io);
goto error;
}

@@ -595,7 +575,7 @@ static void zram_slot_free_notify(struct block_device *bdev,
down_write(&zram->lock);
zram_free_page(zram, index);
up_write(&zram->lock);
- zram_stat64_inc(zram, &zram->stats.notify_free);
+ atomic64_inc(&zram->stats.notify_free);
}

static const struct block_device_operations zram_devops = {
@@ -609,7 +589,6 @@ static int create_device(struct zram *zram, int device_id)

init_rwsem(&zram->lock);
init_rwsem(&zram->init_lock);
- spin_lock_init(&zram->stat64_lock);

zram->queue = blk_alloc_queue(GFP_KERNEL);
if (!zram->queue) {
diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
index b3a315d..11b09fc 100644
--- a/drivers/staging/zram/zram_drv.h
+++ b/drivers/staging/zram/zram_drv.h
@@ -69,14 +69,18 @@ struct table {
u8 flags;
} __aligned(4);

+/*
+ * All 64bit fields should only be manipulated by 64bit atomic accessors.
+ * All modifications to 32bit counter should be protected by zram->lock.
+ */
struct zram_stats {
- u64 compr_size; /* compressed size of pages stored */
- u64 num_reads; /* failed + successful */
- u64 num_writes; /* --do-- */
- u64 failed_reads; /* should NEVER! happen */
- u64 failed_writes; /* can happen when memory is too low */
- u64 invalid_io; /* non-page-aligned I/O requests */
- u64 notify_free; /* no. of swap slot free notifications */
+ atomic64_t compr_size; /* compressed size of pages stored */
+ atomic64_t num_reads; /* failed + successful */
+ atomic64_t num_writes; /* --do-- */
+ atomic64_t failed_reads; /* should NEVER! happen */
+ atomic64_t failed_writes; /* can happen when memory is too low */
+ atomic64_t invalid_io; /* non-page-aligned I/O requests */
+ atomic64_t notify_free; /* no. of swap slot free notifications */
u32 pages_zero; /* no. of zero filled pages */
u32 pages_stored; /* no. of pages currently stored */
u32 good_compress; /* % of pages with compression ratio<=50% */
@@ -92,7 +96,6 @@ struct zram_meta {

struct zram {
struct zram_meta *meta;
- spinlock_t stat64_lock; /* protect 64-bit stats */
struct rw_semaphore lock; /* protect compression buffers, table,
* 32bit stat counters against concurrent
* notifications, reads and writes */
diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
index e239d94..93a2f9c 100644
--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -19,17 +19,6 @@

#include "zram_drv.h"

-static u64 zram_stat64_read(struct zram *zram, u64 *v)
-{
- u64 val;
-
- spin_lock(&zram->stat64_lock);
- val = *v;
- spin_unlock(&zram->stat64_lock);
-
- return val;
-}
-
static inline struct zram *dev_to_zram(struct device *dev)
{
return (struct zram *)dev_to_disk(dev)->private_data;
@@ -116,7 +105,7 @@ static ssize_t num_reads_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);

return sprintf(buf, "%llu\n",
- zram_stat64_read(zram, &zram->stats.num_reads));
+ (u64)atomic64_read(&zram->stats.num_reads));
}

static ssize_t num_writes_show(struct device *dev,
@@ -125,7 +114,7 @@ static ssize_t num_writes_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);

return sprintf(buf, "%llu\n",
- zram_stat64_read(zram, &zram->stats.num_writes));
+ (u64)atomic64_read(&zram->stats.num_writes));
}

static ssize_t invalid_io_show(struct device *dev,
@@ -134,7 +123,7 @@ static ssize_t invalid_io_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);

return sprintf(buf, "%llu\n",
- zram_stat64_read(zram, &zram->stats.invalid_io));
+ (u64)atomic64_read(&zram->stats.invalid_io));
}

static ssize_t notify_free_show(struct device *dev,
@@ -143,7 +132,7 @@ static ssize_t notify_free_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);

return sprintf(buf, "%llu\n",
- zram_stat64_read(zram, &zram->stats.notify_free));
+ (u64)atomic64_read(&zram->stats.notify_free));
}

static ssize_t zero_pages_show(struct device *dev,
@@ -169,7 +158,7 @@ static ssize_t compr_data_size_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);

return sprintf(buf, "%llu\n",
- zram_stat64_read(zram, &zram->stats.compr_size));
+ (u64)atomic64_read(&zram->stats.compr_size));
}

static ssize_t mem_used_total_show(struct device *dev,
--
1.8.1.2


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