zram: use atomic64_xxx() to replace zram_stat64_xxx()

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 4b30fe5..ec2b2b5 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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,