Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 92967471 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

zram: introduce zram->tb_lock 



Currently, the zram table is protected by zram->lock but it's rather
coarse-grained lock and it makes hard for scalibility.

Let's use own rwlock instead of depending on zram->lock.  This patch
adds new locking so obviously, it would make slow but this patch is just
prepartion for removing coarse-grained rw_semaphore(ie, zram->lock)
which is hurdle about zram scalability.

Final patch in this patchset series will remove the lock from read-path
and change rw_semaphore with mutex in write path.  With bonus, we could
drop pending slot free mess in next patch.

Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent deb0bdeb

drivers/block/zram/zram_drv.c

+21 −5
Original line number Diff line number Diff line
@@ -140,6 +140,7 @@ static ssize_t mem_used_total_show(struct device *dev, 
	return sprintf(buf, "%llu\n", val);

}



/* flag operations needs meta->tb_lock */

static int zram_test_flag(struct zram_meta *meta, u32 index,

			enum zram_pageflags flag)

{
@@ -228,6 +229,7 @@ static struct zram_meta *zram_meta_alloc(u64 disksize) 
		goto free_table;

	}



	rwlock_init(&meta->tb_lock);

	return meta;



free_table:
@@ -280,6 +282,7 @@ static void handle_zero_page(struct bio_vec *bvec) 
	flush_dcache_page(page);

}



/* NOTE: caller should hold meta->tb_lock with write-side */

static void zram_free_page(struct zram *zram, size_t index)

{

	struct zram_meta *meta = zram->meta;
@@ -319,20 +322,26 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index) 
	size_t clen = PAGE_SIZE;

	unsigned char *cmem;

	struct zram_meta *meta = zram->meta;

	unsigned long handle = meta->table[index].handle;

	unsigned long handle;

	u16 size;



	read_lock(&meta->tb_lock);

	handle = meta->table[index].handle;

	size = meta->table[index].size;



	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {

		read_unlock(&meta->tb_lock);

		clear_page(mem);

		return 0;

	}



	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);

	if (meta->table[index].size == PAGE_SIZE)

	if (size == PAGE_SIZE)

		copy_page(mem, cmem);

	else

		ret = lzo1x_decompress_safe(cmem, meta->table[index].size,

						mem, &clen);

		ret = lzo1x_decompress_safe(cmem, size,	mem, &clen);

	zs_unmap_object(meta->mem_pool, handle);

	read_unlock(&meta->tb_lock);



	/* Should NEVER happen. Return bio error if it does. */

	if (unlikely(ret != LZO_E_OK)) {
@@ -353,11 +362,14 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, 
	struct zram_meta *meta = zram->meta;

	page = bvec->bv_page;



	read_lock(&meta->tb_lock);

	if (unlikely(!meta->table[index].handle) ||

			zram_test_flag(meta, index, ZRAM_ZERO)) {

		read_unlock(&meta->tb_lock);

		handle_zero_page(bvec);

		return 0;

	}

	read_unlock(&meta->tb_lock);



	if (is_partial_io(bvec))

		/* Use  a temporary buffer to decompress the page */
@@ -433,10 +445,12 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, 
	if (page_zero_filled(uncmem)) {

		kunmap_atomic(user_mem);

		/* Free memory associated with this sector now. */

		write_lock(&zram->meta->tb_lock);

		zram_free_page(zram, index);

		zram_set_flag(meta, index, ZRAM_ZERO);

		write_unlock(&zram->meta->tb_lock);



		atomic_inc(&zram->stats.pages_zero);

		zram_set_flag(meta, index, ZRAM_ZERO);

		ret = 0;

		goto out;

	}
@@ -486,10 +500,12 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, 
	 * Free memory associated with this sector

	 * before overwriting unused sectors.

	 */

	write_lock(&zram->meta->tb_lock);

	zram_free_page(zram, index);



	meta->table[index].handle = handle;

	meta->table[index].size = clen;

	write_unlock(&zram->meta->tb_lock);



	/* Update stats */

	atomic64_add(clen, &zram->stats.compr_size);

drivers/block/zram/zram_drv.h

+2 −1
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ struct zram_stats { 
};



struct zram_meta {

	rwlock_t tb_lock;	/* protect table */

	void *compress_workmem;

	void *compress_buffer;

	struct table *table;
@@ -96,7 +97,7 @@ struct zram_slot_free { 


struct zram {

	struct zram_meta *meta;

	struct rw_semaphore lock; /* protect compression buffers, table,

	struct rw_semaphore lock; /* protect compression buffers,

				   * reads and writes

				   */