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-rw-r--r--Documentation/blockdev/zram.txt6
-rw-r--r--drivers/block/zram/zram_drv.c87
-rw-r--r--drivers/block/zram/zram_drv.h9
3 files changed, 69 insertions, 33 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 1c0c08d9206b..4fced8a21307 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -201,8 +201,8 @@ File /sys/block/zram<id>/mm_stat
The stat file represents device's mm statistics. It consists of a single
line of text and contains the following stats separated by whitespace:
orig_data_size uncompressed size of data stored in this disk.
- This excludes zero-filled pages (zero_pages) since no
- memory is allocated for them.
+ This excludes same-element-filled pages (same_pages) since
+ no memory is allocated for them.
Unit: bytes
compr_data_size compressed size of data stored in this disk
mem_used_total the amount of memory allocated for this disk. This
@@ -214,7 +214,7 @@ line of text and contains the following stats separated by whitespace:
the compressed data
mem_used_max the maximum amount of memory zram have consumed to
store the data
- zero_pages the number of zero filled pages written to this disk.
+ same_pages the number of same element filled pages written to this disk.
No memory is allocated for such pages.
pages_compacted the number of pages freed during compaction
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 662d62878e47..e27d89a36c34 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -74,6 +74,17 @@ static void zram_clear_flag(struct zram_meta *meta, u32 index,
meta->table[index].value &= ~BIT(flag);
}
+static inline void zram_set_element(struct zram_meta *meta, u32 index,
+ unsigned long element)
+{
+ meta->table[index].element = element;
+}
+
+static inline void zram_clear_element(struct zram_meta *meta, u32 index)
+{
+ meta->table[index].element = 0;
+}
+
static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
{
return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
@@ -146,31 +157,46 @@ static inline void update_used_max(struct zram *zram,
} while (old_max != cur_max);
}
-static bool page_zero_filled(void *ptr)
+static inline void zram_fill_page(char *ptr, unsigned long len,
+ unsigned long value)
+{
+ int i;
+ unsigned long *page = (unsigned long *)ptr;
+
+ WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long)));
+
+ if (likely(value == 0)) {
+ memset(ptr, 0, len);
+ } else {
+ for (i = 0; i < len / sizeof(*page); i++)
+ page[i] = value;
+ }
+}
+
+static bool page_same_filled(void *ptr, unsigned long *element)
{
unsigned int pos;
unsigned long *page;
page = (unsigned long *)ptr;
- for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
- if (page[pos])
+ for (pos = 0; pos < PAGE_SIZE / sizeof(*page) - 1; pos++) {
+ if (page[pos] != page[pos + 1])
return false;
}
+ *element = page[pos];
+
return true;
}
-static void handle_zero_page(struct bio_vec *bvec)
+static void handle_same_page(struct bio_vec *bvec, unsigned long element)
{
struct page *page = bvec->bv_page;
void *user_mem;
user_mem = kmap_atomic(page);
- if (is_partial_io(bvec))
- memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
- else
- clear_page(user_mem);
+ zram_fill_page(user_mem + bvec->bv_offset, bvec->bv_len, element);
kunmap_atomic(user_mem);
flush_dcache_page(page);
@@ -363,7 +389,7 @@ static ssize_t mm_stat_show(struct device *dev,
mem_used << PAGE_SHIFT,
zram->limit_pages << PAGE_SHIFT,
max_used << PAGE_SHIFT,
- (u64)atomic64_read(&zram->stats.zero_pages),
+ (u64)atomic64_read(&zram->stats.same_pages),
pool_stats.pages_compacted);
up_read(&zram->init_lock);
@@ -399,8 +425,11 @@ static void zram_meta_free(struct zram_meta *meta, u64 disksize)
/* Free all pages that are still in this zram device */
for (index = 0; index < num_pages; index++) {
unsigned long handle = meta->table[index].handle;
-
- if (!handle)
+ /*
+ * No memory is allocated for same element filled pages.
+ * Simply clear same page flag.
+ */
+ if (!handle || zram_test_flag(meta, index, ZRAM_SAME))
continue;
zs_free(meta->mem_pool, handle);
@@ -450,18 +479,20 @@ static void zram_free_page(struct zram *zram, size_t index)
struct zram_meta *meta = zram->meta;
unsigned long handle = meta->table[index].handle;
- if (unlikely(!handle)) {
- /*
- * No memory is allocated for zero filled pages.
- * Simply clear zero page flag.
- */
- if (zram_test_flag(meta, index, ZRAM_ZERO)) {
- zram_clear_flag(meta, index, ZRAM_ZERO);
- atomic64_dec(&zram->stats.zero_pages);
- }
+ /*
+ * No memory is allocated for same element filled pages.
+ * Simply clear same page flag.
+ */
+ if (zram_test_flag(meta, index, ZRAM_SAME)) {
+ zram_clear_flag(meta, index, ZRAM_SAME);
+ zram_clear_element(meta, index);
+ atomic64_dec(&zram->stats.same_pages);
return;
}
+ if (!handle)
+ return;
+
zs_free(meta->mem_pool, handle);
atomic64_sub(zram_get_obj_size(meta, index),
@@ -484,9 +515,9 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
handle = meta->table[index].handle;
size = zram_get_obj_size(meta, index);
- if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
+ if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) {
bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
- clear_page(mem);
+ zram_fill_page(mem, PAGE_SIZE, meta->table[index].element);
return 0;
}
@@ -522,9 +553,9 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
if (unlikely(!meta->table[index].handle) ||
- zram_test_flag(meta, index, ZRAM_ZERO)) {
+ zram_test_flag(meta, index, ZRAM_SAME)) {
bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
- handle_zero_page(bvec);
+ handle_same_page(bvec, meta->table[index].element);
return 0;
}
bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
@@ -572,6 +603,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
struct zram_meta *meta = zram->meta;
struct zcomp_strm *zstrm = NULL;
unsigned long alloced_pages;
+ unsigned long element;
page = bvec->bv_page;
if (is_partial_io(bvec)) {
@@ -600,16 +632,17 @@ compress_again:
uncmem = user_mem;
}
- if (page_zero_filled(uncmem)) {
+ if (page_same_filled(uncmem, &element)) {
if (user_mem)
kunmap_atomic(user_mem);
/* Free memory associated with this sector now. */
bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
zram_free_page(zram, index);
- zram_set_flag(meta, index, ZRAM_ZERO);
+ zram_set_flag(meta, index, ZRAM_SAME);
+ zram_set_element(meta, index, element);
bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
- atomic64_inc(&zram->stats.zero_pages);
+ atomic64_inc(&zram->stats.same_pages);
ret = 0;
goto out;
}
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 2692554b7737..caeff51f1571 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -61,7 +61,7 @@ static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
/* Flags for zram pages (table[page_no].value) */
enum zram_pageflags {
/* Page consists entirely of zeros */
- ZRAM_ZERO = ZRAM_FLAG_SHIFT,
+ ZRAM_SAME = ZRAM_FLAG_SHIFT,
ZRAM_ACCESS, /* page is now accessed */
__NR_ZRAM_PAGEFLAGS,
@@ -71,7 +71,10 @@ enum zram_pageflags {
/* Allocated for each disk page */
struct zram_table_entry {
- unsigned long handle;
+ union {
+ unsigned long handle;
+ unsigned long element;
+ };
unsigned long value;
};
@@ -83,7 +86,7 @@ struct zram_stats {
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 */
- atomic64_t zero_pages; /* no. of zero filled pages */
+ atomic64_t same_pages; /* no. of same element filled pages */
atomic64_t pages_stored; /* no. of pages currently stored */
atomic_long_t max_used_pages; /* no. of maximum pages stored */
atomic64_t writestall; /* no. of write slow paths */