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Commit 6a907728 authored by Nitin Gupta's avatar Nitin Gupta Committed by Greg Kroah-Hartman
Browse files

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: default avatarNitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 1994130e

drivers/staging/ramzswap/ramzswap_drv.c

+30 −28
Original line number Diff line number Diff line
@@ -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 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio) 


	/* 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 @@ static int ramzswap_write(struct ramzswap *rzs, struct bio *bio) 


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);

drivers/staging/ramzswap/ramzswap_drv.h

+49 −10
Original line number Diff line number Diff line
@@ -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

drivers/staging/ramzswap/ramzswap_ioctl.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */