Staging: ramzswap: Use lock for 64-bit stats

64-bit stats corruption was observed when ramzswap was
used on SMP systems. To prevent this, use separate spinlock
to protect these stats.

Also, replace stat_*() with rzs_stat*() to avoid possible
conflict with core kernel code.

Eventually, these will be converted to per-cpu counters
if this driver finds use on large scale systems and this
locking is found to affect scalability.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/ramzswap/ramzswap_drv.c b/drivers/staging/ramzswap/ramzswap_drv.c
index baf757259d0bda4a00d43a5219eada9fd7b297fc..05273c0588c6dbbace5014805a5c4060338b52bc 100644 (file)
--- a/drivers/staging/ramzswap/ramzswap_drv.c
+++ b/drivers/staging/ramzswap/ramzswap_drv.c
@@ -24,7 +24,6 @@
 #include <linux/genhd.h>
 #include <linux/highmem.h>
 #include <linux/lzo.h>
-#include <linux/mutex.h>
 #include <linux/string.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
@@ -239,7 +238,8 @@ void ramzswap_ioctl_get_stats(struct ramzswap *rzs,
 
        mem_used = xv_get_total_size_bytes(rzs->mem_pool)
                        + (rs->pages_expand << PAGE_SHIFT);
-       succ_writes = rs->num_writes - rs->failed_writes;
+       succ_writes = rzs_stat64_read(rzs, &rs->num_writes) -
+                       rzs_stat64_read(rzs, &rs->failed_writes);
 
        if (succ_writes && rs->pages_stored) {
                good_compress_perc = rs->good_compress * 100
@@ -248,11 +248,12 @@ void ramzswap_ioctl_get_stats(struct ramzswap *rzs,
                                        / rs->pages_stored;
        }
 
-       s->num_reads = rs->num_reads;
-       s->num_writes = rs->num_writes;
-       s->failed_reads = rs->failed_reads;
-       s->failed_writes = rs->failed_writes;
-       s->invalid_io = rs->invalid_io;
+       s->num_reads = rzs_stat64_read(rzs, &rs->num_reads);
+       s->num_writes = rzs_stat64_read(rzs, &rs->num_writes);
+       s->failed_reads = rzs_stat64_read(rzs, &rs->failed_reads);
+       s->failed_writes = rzs_stat64_read(rzs, &rs->failed_writes);
+       s->invalid_io = rzs_stat64_read(rzs, &rs->invalid_io);
+       s->notify_free = rzs_stat64_read(rzs, &rs->notify_free);
        s->pages_zero = rs->pages_zero;
 
        s->good_compress_pct = good_compress_perc;
@@ -264,8 +265,8 @@ void ramzswap_ioctl_get_stats(struct ramzswap *rzs,
        s->compr_data_size = rs->compr_size;
        s->mem_used_total = mem_used;
 
-       s->bdev_num_reads = rs->bdev_num_reads;
-       s->bdev_num_writes = rs->bdev_num_writes;
+       s->bdev_num_reads = rzs_stat64_read(rzs, &rs->bdev_num_reads);
+       s->bdev_num_writes = rzs_stat64_read(rzs, &rs->bdev_num_writes);
        }
 #endif /* CONFIG_RAMZSWAP_STATS */
 }
@@ -594,7 +595,7 @@ static void ramzswap_free_page(struct ramzswap *rzs, size_t index)
        if (unlikely(!page)) {
                if (rzs_test_flag(rzs, index, RZS_ZERO)) {
                        rzs_clear_flag(rzs, index, RZS_ZERO);
-                       stat_dec(rzs->stats.pages_zero);
+                       rzs_stat_dec(&rzs->stats.pages_zero);
                }
                return;
        }
@@ -603,7 +604,7 @@ static void ramzswap_free_page(struct ramzswap *rzs, size_t index)
                clen = PAGE_SIZE;
                __free_page(page);
                rzs_clear_flag(rzs, index, RZS_UNCOMPRESSED);
-               stat_dec(rzs->stats.pages_expand);
+               rzs_stat_dec(&rzs->stats.pages_expand);
                goto out;
        }
 
@@ -613,11 +614,11 @@ static void ramzswap_free_page(struct ramzswap *rzs, size_t index)
 
        xv_free(rzs->mem_pool, page, offset);
        if (clen <= PAGE_SIZE / 2)
-               stat_dec(rzs->stats.good_compress);
+               rzs_stat_dec(&rzs->stats.good_compress);
 
 out:
        rzs->stats.compr_size -= clen;
-       stat_dec(rzs->stats.pages_stored);
+       rzs_stat_dec(&rzs->stats.pages_stored);
 
        rzs->table[index].page = NULL;
        rzs->table[index].offset = 0;
@@ -679,8 +680,8 @@ static int handle_ramzswap_fault(struct ramzswap *rzs, struct bio *bio)
         */
        if (rzs->backing_swap) {
                u32 pagenum;
-               stat_dec(rzs->stats.num_reads);
-               stat_inc(rzs->stats.bdev_num_reads);
+               rzs_stat64_dec(rzs, &rzs->stats.num_reads);
+               rzs_stat64_inc(rzs, &rzs->stats.bdev_num_reads);
                bio->bi_bdev = rzs->backing_swap;
 
                /*
@@ -718,7 +719,7 @@ static int ramzswap_read(struct ramzswap *rzs, struct bio *bio)
        struct zobj_header *zheader;
        unsigned char *user_mem, *cmem;
 
-       stat_inc(rzs->stats.num_reads);
+       rzs_stat64_inc(rzs, &rzs->stats.num_reads);
 
        page = bio->bi_io_vec[0].bv_page;
        index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
@@ -752,7 +753,7 @@ static int ramzswap_read(struct ramzswap *rzs, struct bio *bio)
        if (unlikely(ret != LZO_E_OK)) {
                pr_err("Decompression failed! err=%d, page=%u\n",
                        ret, index);
-               stat_inc(rzs->stats.failed_reads);
+               rzs_stat64_inc(rzs, &rzs->stats.failed_reads);
                goto out;
        }
 
@@ -776,7 +777,7 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
        struct page *page, *page_store;
        unsigned char *user_mem, *cmem, *src;
 
-       stat_inc(rzs->stats.num_writes);
+       rzs_stat64_inc(rzs, &rzs->stats.num_writes);
 
        page = bio->bi_io_vec[0].bv_page;
        index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
@@ -796,7 +797,7 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
         * Simply clear zero page flag.
         */
        if (rzs_test_flag(rzs, index, RZS_ZERO)) {
-               stat_dec(rzs->stats.pages_zero);
+               rzs_stat_dec(&rzs->stats.pages_zero);
                rzs_clear_flag(rzs, index, RZS_ZERO);
        }
 
@@ -806,7 +807,7 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
        if (page_zero_filled(user_mem)) {
                kunmap_atomic(user_mem, KM_USER0);
                mutex_unlock(&rzs->lock);
-               stat_inc(rzs->stats.pages_zero);
+               rzs_stat_inc(&rzs->stats.pages_zero);
                rzs_set_flag(rzs, index, RZS_ZERO);
 
                set_bit(BIO_UPTODATE, &bio->bi_flags);
@@ -830,7 +831,7 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
        if (unlikely(ret != LZO_E_OK)) {
                mutex_unlock(&rzs->lock);
                pr_err("Compression failed! err=%d\n", ret);
-               stat_inc(rzs->stats.failed_writes);
+               rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
                goto out;
        }
 
@@ -853,13 +854,13 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
                        mutex_unlock(&rzs->lock);
                        pr_info("Error allocating memory for incompressible "
                                "page: %u\n", index);
-                       stat_inc(rzs->stats.failed_writes);
+                       rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
                        goto out;
                }
 
                offset = 0;
                rzs_set_flag(rzs, index, RZS_UNCOMPRESSED);
-               stat_inc(rzs->stats.pages_expand);
+               rzs_stat_inc(&rzs->stats.pages_expand);
                rzs->table[index].page = page_store;
                src = kmap_atomic(page, KM_USER0);
                goto memstore;
@@ -871,7 +872,7 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
                mutex_unlock(&rzs->lock);
                pr_info("Error allocating memory for compressed "
                        "page: %u, size=%zu\n", index, clen);
-               stat_inc(rzs->stats.failed_writes);
+               rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
                if (rzs->backing_swap)
                        fwd_write_request = 1;
                goto out;
@@ -900,9 +901,9 @@ memstore:
 
        /* Update stats */
        rzs->stats.compr_size += clen;
-       stat_inc(rzs->stats.pages_stored);
+       rzs_stat_inc(&rzs->stats.pages_stored);
        if (clen <= PAGE_SIZE / 2)
-               stat_inc(rzs->stats.good_compress);
+               rzs_stat_inc(&rzs->stats.good_compress);
 
        mutex_unlock(&rzs->lock);
 
@@ -912,7 +913,7 @@ memstore:
 
 out:
        if (fwd_write_request) {
-               stat_inc(rzs->stats.bdev_num_writes);
+               rzs_stat64_inc(rzs, &rzs->stats.bdev_num_writes);
                bio->bi_bdev = rzs->backing_swap;
 #if 0
                /*
@@ -974,7 +975,7 @@ static int ramzswap_make_request(struct request_queue *queue, struct bio *bio)
        }
 
        if (!valid_swap_request(rzs, bio)) {
-               stat_inc(rzs->stats.invalid_io);
+               rzs_stat64_inc(rzs, &rzs->stats.invalid_io);
                bio_io_error(bio);
                return 0;
        }
@@ -1295,6 +1296,7 @@ static struct block_device_operations ramzswap_devops = {
 static int create_device(struct ramzswap *rzs, int device_id)
 {
        mutex_init(&rzs->lock);
+       spin_lock_init(&rzs->stat64_lock);
        INIT_LIST_HEAD(&rzs->backing_swap_extent_list);
 
        rzs->queue = blk_alloc_queue(GFP_KERNEL);

diff --git a/drivers/staging/ramzswap/ramzswap_drv.h b/drivers/staging/ramzswap/ramzswap_drv.h
index 7ba98bfee2d6d1271ccc20dac1bbb064a1a3cc41..5b672225e174aee0164c8d801e9baeaec65464fe 100644 (file)
--- a/drivers/staging/ramzswap/ramzswap_drv.h
+++ b/drivers/staging/ramzswap/ramzswap_drv.h
@@ -15,6 +15,9 @@
 #ifndef _RAMZSWAP_DRV_H_
 #define _RAMZSWAP_DRV_H_
 
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+
 #include "ramzswap_ioctl.h"
 #include "xvmalloc.h"
 
@@ -71,15 +74,6 @@ static const unsigned max_zpage_size_nobdev = PAGE_SIZE / 4 * 3;
 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
 #define SECTORS_PER_PAGE       (1 << SECTORS_PER_PAGE_SHIFT)
 
-/* Debugging and Stats */
-#if defined(CONFIG_RAMZSWAP_STATS)
-#define stat_inc(stat) ((stat)++)
-#define stat_dec(stat) ((stat)--)
-#else
-#define stat_inc(x)
-#define stat_dec(x)
-#endif
-
 /* Flags for ramzswap pages (table[page_no].flags) */
 enum rzs_pageflags {
        /* Page is stored uncompressed */
@@ -124,6 +118,7 @@ struct ramzswap_stats {
        u64 failed_reads;       /* should NEVER! happen */
        u64 failed_writes;      /* can happen when memory is too low */
        u64 invalid_io;         /* non-swap I/O requests */
+       u64 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% */
@@ -138,6 +133,7 @@ struct ramzswap {
        void *compress_workmem;
        void *compress_buffer;
        struct table *table;
+       spinlock_t stat64_lock; /* protect 64-bit stats */
        struct mutex lock;
        struct request_queue *queue;
        struct gendisk *disk;
@@ -167,5 +163,48 @@ struct ramzswap {
 
 /*-- */
 
-#endif
+/* Debugging and Stats */
+#if defined(CONFIG_RAMZSWAP_STATS)
+static void rzs_stat_inc(u32 *v)
+{
+       *v = *v + 1;
+}
+
+static void rzs_stat_dec(u32 *v)
+{
+       *v = *v - 1;
+}
+
+static void rzs_stat64_inc(struct ramzswap *rzs, u64 *v)
+{
+       spin_lock(&rzs->stat64_lock);
+       *v = *v + 1;
+       spin_unlock(&rzs->stat64_lock);
+}
+
+static void rzs_stat64_dec(struct ramzswap *rzs, u64 *v)
+{
+       spin_lock(&rzs->stat64_lock);
+       *v = *v - 1;
+       spin_unlock(&rzs->stat64_lock);
+}
+
+static u64 rzs_stat64_read(struct ramzswap *rzs, u64 *v)
+{
+       u64 val;
+
+       spin_lock(&rzs->stat64_lock);
+       val = *v;
+       spin_unlock(&rzs->stat64_lock);
+
+       return val;
+}
+#else
+#define rzs_stat_inc(v)
+#define rzs_stat_dec(v)
+#define rzs_stat64_inc(r, v)
+#define rzs_stat64_dec(r, v)
+#define rzs_stat64_read(r, v)
+#endif /* CONFIG_RAMZSWAP_STATS */
 
+#endif

diff --git a/drivers/staging/ramzswap/ramzswap_ioctl.h b/drivers/staging/ramzswap/ramzswap_ioctl.h
index 1bc54e22c915ac6bd257a2d3f75291f2ea70b710..1edaebaaf81df969b5017446868820e3a277bee1 100644 (file)
--- a/drivers/staging/ramzswap/ramzswap_ioctl.h
+++ b/drivers/staging/ramzswap/ramzswap_ioctl.h
@@ -27,6 +27,7 @@ struct ramzswap_ioctl_stats {
        u64 failed_reads;       /* should NEVER! happen */
        u64 failed_writes;      /* can happen when memory is too low */
        u64 invalid_io;         /* non-swap I/O requests */
+       u64 notify_free;        /* no. of swap slot free notifications */
        u32 pages_zero;         /* no. of zero filled pages */
        u32 good_compress_pct;  /* no. of pages with compression ratio<=50% */
        u32 pages_expand_pct;   /* no. of incompressible pages */