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-rw-r--r--drivers/block/zram/zram_drv.c69
-rw-r--r--drivers/block/zram/zram_drv.h24
2 files changed, 60 insertions, 33 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index efd9e4f1605c..a21f466c4e15 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -183,19 +183,32 @@ static ssize_t comp_algorithm_store(struct device *dev,
static int zram_test_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
{
- return meta->table[index].flags & BIT(flag);
+ return meta->table[index].value & BIT(flag);
}
static void zram_set_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
{
- meta->table[index].flags |= BIT(flag);
+ meta->table[index].value |= BIT(flag);
}
static void zram_clear_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
{
- meta->table[index].flags &= ~BIT(flag);
+ meta->table[index].value &= ~BIT(flag);
+}
+
+static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
+{
+ return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
+}
+
+static void zram_set_obj_size(struct zram_meta *meta,
+ u32 index, size_t size)
+{
+ unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
+
+ meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
}
static inline int is_partial_io(struct bio_vec *bvec)
@@ -254,7 +267,6 @@ static struct zram_meta *zram_meta_alloc(u64 disksize)
goto free_table;
}
- rwlock_init(&meta->tb_lock);
return meta;
free_table:
@@ -303,7 +315,12 @@ static void handle_zero_page(struct bio_vec *bvec)
flush_dcache_page(page);
}
-/* NOTE: caller should hold meta->tb_lock with write-side */
+
+/*
+ * To protect concurrent access to the same index entry,
+ * caller should hold this table index entry's bit_spinlock to
+ * indicate this index entry is accessing.
+ */
static void zram_free_page(struct zram *zram, size_t index)
{
struct zram_meta *meta = zram->meta;
@@ -323,11 +340,12 @@ static void zram_free_page(struct zram *zram, size_t index)
zs_free(meta->mem_pool, handle);
- atomic64_sub(meta->table[index].size, &zram->stats.compr_data_size);
+ atomic64_sub(zram_get_obj_size(meta, index),
+ &zram->stats.compr_data_size);
atomic64_dec(&zram->stats.pages_stored);
meta->table[index].handle = 0;
- meta->table[index].size = 0;
+ zram_set_obj_size(meta, index, 0);
}
static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
@@ -338,12 +356,12 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
unsigned long handle;
size_t size;
- read_lock(&meta->tb_lock);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
handle = meta->table[index].handle;
- size = meta->table[index].size;
+ size = zram_get_obj_size(meta, index);
if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
- read_unlock(&meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
clear_page(mem);
return 0;
}
@@ -354,7 +372,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
else
ret = zcomp_decompress(zram->comp, cmem, size, mem);
zs_unmap_object(meta->mem_pool, handle);
- read_unlock(&meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
/* Should NEVER happen. Return bio error if it does. */
if (unlikely(ret)) {
@@ -375,14 +393,14 @@ 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);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
if (unlikely(!meta->table[index].handle) ||
zram_test_flag(meta, index, ZRAM_ZERO)) {
- read_unlock(&meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
handle_zero_page(bvec);
return 0;
}
- read_unlock(&meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
if (is_partial_io(bvec))
/* Use a temporary buffer to decompress the page */
@@ -460,10 +478,10 @@ 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);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
zram_free_page(zram, index);
zram_set_flag(meta, index, ZRAM_ZERO);
- write_unlock(&zram->meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
atomic64_inc(&zram->stats.zero_pages);
ret = 0;
@@ -513,12 +531,12 @@ 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);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
zram_free_page(zram, index);
meta->table[index].handle = handle;
- meta->table[index].size = clen;
- write_unlock(&zram->meta->tb_lock);
+ zram_set_obj_size(meta, index, clen);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
/* Update stats */
atomic64_add(clen, &zram->stats.compr_data_size);
@@ -559,6 +577,7 @@ static void zram_bio_discard(struct zram *zram, u32 index,
int offset, struct bio *bio)
{
size_t n = bio->bi_size;
+ struct zram_meta *meta = zram->meta;
/*
* zram manages data in physical block size units. Because logical block
@@ -579,13 +598,9 @@ static void zram_bio_discard(struct zram *zram, u32 index,
}
while (n >= PAGE_SIZE) {
- /*
- * Discard request can be large so the lock hold times could be
- * lengthy. So take the lock once per page.
- */
- write_lock(&zram->meta->tb_lock);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
zram_free_page(zram, index);
- write_unlock(&zram->meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
index++;
n -= PAGE_SIZE;
}
@@ -819,9 +834,9 @@ static void zram_slot_free_notify(struct block_device *bdev,
zram = bdev->bd_disk->private_data;
meta = zram->meta;
- write_lock(&meta->tb_lock);
+ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
zram_free_page(zram, index);
- write_unlock(&meta->tb_lock);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
atomic64_inc(&zram->stats.notify_free);
}
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index c8161bd8969c..5b0afde729cd 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -50,10 +50,24 @@ static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
-/* Flags for zram pages (table[page_no].flags) */
+
+/*
+ * The lower ZRAM_FLAG_SHIFT bits of table.value is for
+ * object size (excluding header), the higher bits is for
+ * zram_pageflags.
+ *
+ * zram is mainly used for memory efficiency so we want to keep memory
+ * footprint small so we can squeeze size and flags into a field.
+ * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
+ * the higher bits is for zram_pageflags.
+ */
+#define ZRAM_FLAG_SHIFT 24
+
+/* Flags for zram pages (table[page_no].value) */
enum zram_pageflags {
/* Page consists entirely of zeros */
- ZRAM_ZERO,
+ ZRAM_ZERO = ZRAM_FLAG_SHIFT + 1,
+ ZRAM_ACCESS, /* page in now accessed */
__NR_ZRAM_PAGEFLAGS,
};
@@ -63,9 +77,8 @@ enum zram_pageflags {
/* Allocated for each disk page */
struct zram_table_entry {
unsigned long handle;
- u16 size; /* object size (excluding header) */
- u8 flags;
-} __aligned(4);
+ unsigned long value;
+};
struct zram_stats {
atomic64_t compr_data_size; /* compressed size of pages stored */
@@ -80,7 +93,6 @@ struct zram_stats {
};
struct zram_meta {
- rwlock_t tb_lock; /* protect table */
struct zram_table_entry *table;
struct zs_pool *mem_pool;
};