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Subject[PATCH v3 1/4] zram: introduce zram_entry to prepare dedup functionality
Date
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Following patch will implement deduplication functionality
in the zram and it requires an indirection layer to manage
the life cycle of zsmalloc handle. To prepare that, this patch
introduces zram_entry which can be used to manage the life-cycle
of zsmalloc handle. Many lines are changed due to rename but
core change is just simple introduction about newly data structure.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
drivers/block/zram/zram_drv.c | 95 +++++++++++++++++++++++++++----------------
drivers/block/zram/zram_drv.h | 6 ++-
2 files changed, 66 insertions(+), 35 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index debee95..26dc4e5 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -57,14 +57,15 @@ static inline struct zram *dev_to_zram(struct device *dev)
return (struct zram *)dev_to_disk(dev)->private_data;
}

-static unsigned long zram_get_handle(struct zram *zram, u32 index)
+static struct zram_entry *zram_get_entry(struct zram *zram, u32 index)
{
- return zram->table[index].handle;
+ return zram->table[index].entry;
}

-static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
+static void zram_set_entry(struct zram *zram, u32 index,
+ struct zram_entry *entry)
{
- zram->table[index].handle = handle;
+ zram->table[index].entry = entry;
}

/* flag operations require table entry bit_spin_lock() being held */
@@ -437,7 +438,7 @@ static bool zram_same_page_read(struct zram *zram, u32 index,
unsigned int offset, unsigned int len)
{
zram_slot_lock(zram, index);
- if (unlikely(!zram_get_handle(zram, index) ||
+ if (unlikely(!zram_get_entry(zram, index) ||
zram_test_flag(zram, index, ZRAM_SAME))) {
void *mem;

@@ -476,6 +477,32 @@ static bool zram_same_page_write(struct zram *zram, u32 index,
return false;
}

+static struct zram_entry *zram_entry_alloc(struct zram *zram,
+ unsigned int len, gfp_t flags)
+{
+ struct zram_entry *entry;
+
+ entry = kzalloc(sizeof(*entry),
+ flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
+ if (!entry)
+ return NULL;
+
+ entry->handle = zs_malloc(zram->mem_pool, len, flags);
+ if (!entry->handle) {
+ kfree(entry);
+ return NULL;
+ }
+
+ return entry;
+}
+
+static inline void zram_entry_free(struct zram *zram,
+ struct zram_entry *entry)
+{
+ zs_free(zram->mem_pool, entry->handle);
+ kfree(entry);
+}
+
static void zram_meta_free(struct zram *zram, u64 disksize)
{
size_t num_pages = disksize >> PAGE_SHIFT;
@@ -514,7 +541,7 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
*/
static void zram_free_page(struct zram *zram, size_t index)
{
- unsigned long handle = zram_get_handle(zram, index);
+ struct zram_entry *entry = zram_get_entry(zram, index);

/*
* No memory is allocated for same element filled pages.
@@ -527,23 +554,23 @@ static void zram_free_page(struct zram *zram, size_t index)
return;
}

- if (!handle)
+ if (!entry)
return;

- zs_free(zram->mem_pool, handle);
+ zram_entry_free(zram, entry);

atomic64_sub(zram_get_obj_size(zram, index),
&zram->stats.compr_data_size);
atomic64_dec(&zram->stats.pages_stored);

- zram_set_handle(zram, index, 0);
+ zram_set_entry(zram, index, NULL);
zram_set_obj_size(zram, index, 0);
}

static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
{
int ret;
- unsigned long handle;
+ struct zram_entry *entry;
unsigned int size;
void *src, *dst;

@@ -551,10 +578,10 @@ static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
return 0;

zram_slot_lock(zram, index);
- handle = zram_get_handle(zram, index);
+ entry = zram_get_entry(zram, index);
size = zram_get_obj_size(zram, index);

- src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
+ src = zs_map_object(zram->mem_pool, entry->handle, ZS_MM_RO);
if (size == PAGE_SIZE) {
dst = kmap_atomic(page);
memcpy(dst, src, PAGE_SIZE);
@@ -568,7 +595,7 @@ static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
kunmap_atomic(dst);
zcomp_stream_put(zram->comp);
}
- zs_unmap_object(zram->mem_pool, handle);
+ zs_unmap_object(zram->mem_pool, entry->handle);
zram_slot_unlock(zram, index);

/* Should NEVER happen. Return bio error if it does. */
@@ -612,14 +639,14 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
}

static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
- struct page *page,
- unsigned long *out_handle, unsigned int *out_comp_len)
+ struct page *page, struct zram_entry **out_entry,
+ unsigned int *out_comp_len)
{
int ret;
unsigned int comp_len;
void *src;
unsigned long alloced_pages;
- unsigned long handle = 0;
+ struct zram_entry *entry = NULL;

compress_again:
src = kmap_atomic(page);
@@ -628,8 +655,8 @@ static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,

if (unlikely(ret)) {
pr_err("Compression failed! err=%d\n", ret);
- if (handle)
- zs_free(zram->mem_pool, handle);
+ if (entry)
+ zram_entry_free(zram, entry);
return ret;
}

@@ -637,32 +664,32 @@ static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
comp_len = PAGE_SIZE;

/*
- * handle allocation has 2 paths:
+ * entry allocation has 2 paths:
* a) fast path is executed with preemption disabled (for
* per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
* since we can't sleep;
* b) slow path enables preemption and attempts to allocate
* the page with __GFP_DIRECT_RECLAIM bit set. we have to
* put per-cpu compression stream and, thus, to re-do
- * the compression once handle is allocated.
+ * the compression once entry is allocated.
*
- * if we have a 'non-null' handle here then we are coming
- * from the slow path and handle has already been allocated.
+ * if we have a 'non-null' entry here then we are coming
+ * from the slow path and entry has already been allocated.
*/
- if (!handle)
- handle = zs_malloc(zram->mem_pool, comp_len,
+ if (!entry)
+ entry = zram_entry_alloc(zram, comp_len,
__GFP_KSWAPD_RECLAIM |
__GFP_NOWARN |
__GFP_HIGHMEM |
__GFP_MOVABLE);
- if (!handle) {
+ if (!entry) {
zcomp_stream_put(zram->comp);
atomic64_inc(&zram->stats.writestall);
- handle = zs_malloc(zram->mem_pool, comp_len,
+ entry = zram_entry_alloc(zram, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
__GFP_MOVABLE);
*zstrm = zcomp_stream_get(zram->comp);
- if (handle)
+ if (entry)
goto compress_again;
return -ENOMEM;
}
@@ -671,11 +698,11 @@ static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
update_used_max(zram, alloced_pages);

if (zram->limit_pages && alloced_pages > zram->limit_pages) {
- zs_free(zram->mem_pool, handle);
+ zram_entry_free(zram, entry);
return -ENOMEM;
}

- *out_handle = handle;
+ *out_entry = entry;
*out_comp_len = comp_len;
return 0;
}
@@ -683,7 +710,7 @@ static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
{
int ret;
- unsigned long handle;
+ struct zram_entry *entry;
unsigned int comp_len;
void *src, *dst;
struct zcomp_strm *zstrm;
@@ -693,13 +720,13 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
return 0;

zstrm = zcomp_stream_get(zram->comp);
- ret = zram_compress(zram, &zstrm, page, &handle, &comp_len);
+ ret = zram_compress(zram, &zstrm, page, &entry, &comp_len);
if (ret) {
zcomp_stream_put(zram->comp);
return ret;
}

- dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
+ dst = zs_map_object(zram->mem_pool, entry->handle, ZS_MM_WO);

src = zstrm->buffer;
if (comp_len == PAGE_SIZE)
@@ -709,7 +736,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
kunmap_atomic(src);

zcomp_stream_put(zram->comp);
- zs_unmap_object(zram->mem_pool, handle);
+ zs_unmap_object(zram->mem_pool, entry->handle);

/*
* Free memory associated with this sector
@@ -717,7 +744,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
*/
zram_slot_lock(zram, index);
zram_free_page(zram, index);
- zram_set_handle(zram, index, handle);
+ zram_set_entry(zram, index, entry);
zram_set_obj_size(zram, index, comp_len);
zram_slot_unlock(zram, index);

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index e34e44d..fe3d216 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -69,10 +69,14 @@ enum zram_pageflags {

/*-- Data structures */

+struct zram_entry {
+ unsigned long handle;
+};
+
/* Allocated for each disk page */
struct zram_table_entry {
union {
- unsigned long handle;
+ struct zram_entry *entry;
unsigned long element;
};
unsigned long value;
--
2.7.4
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