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zram: introduce zram_entry to prepare dedup functionality
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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.

Change-Id: Ibf9912397c8c7dbcf1465550bc83a71f904e41c7
Reviewed-by: Sergey Senozhatsky <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Signed-off-by: Joonsoo Kim <[email protected]>
Link: https://lore.kernel.org/patchwork/patch/787161/
Patch-mainline: linux-kernel@ Thu, 11 May 2017 22:30:21
Signed-off-by: Charan Teja Reddy <[email protected]>
Signed-off-by: Park Ju Hyung <[email protected]>
Signed-off-by: Alexander Winkowski <[email protected]>
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@JoonsooKim @dereference23
JoonsooKim authored and dereference23 committed Aug 24, 2022
1 parent 94b7fcf commit 5b4b8a6
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Showing 2 changed files with 63 additions and 31 deletions.
88 changes: 58 additions & 30 deletions drivers/block/zram/zram_drv.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -85,14 +85,15 @@ 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 */
Expand Down Expand Up @@ -1171,6 +1172,32 @@ static DEVICE_ATTR_RO(bd_stat);
#endif
static DEVICE_ATTR_RO(debug_stat);

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;
Expand Down Expand Up @@ -1211,7 +1238,7 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
*/
static void zram_free_page(struct zram *zram, size_t index)
{
unsigned long handle;
struct zram_entry *entry;

#ifdef CONFIG_ZRAM_MEMORY_TRACKING
zram->table[index].ac_time = 0;
Expand Down Expand Up @@ -1240,17 +1267,17 @@ static void zram_free_page(struct zram *zram, size_t index)
goto out;
}

handle = zram_get_handle(zram, index);
if (!handle)
entry = zram_get_entry(zram, index);
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);
out:
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);
WARN_ON_ONCE(zram->table[index].flags &
~(1UL << ZRAM_LOCK | 1UL << ZRAM_UNDER_WB));
Expand All @@ -1260,7 +1287,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
struct bio *bio, bool partial_io)
{
struct zcomp_strm *zstrm;
unsigned long handle;
struct zram_entry *entry;
unsigned int size;
void *src, *dst;
int ret;
Expand All @@ -1279,12 +1306,12 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
bio, partial_io);
}

handle = zram_get_handle(zram, index);
if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
entry = zram_get_entry(zram, index);
if (!entry || zram_test_flag(zram, index, ZRAM_SAME)) {
unsigned long value;
void *mem;

value = handle ? zram_get_element(zram, index) : 0;
value = entry ? zram_get_element(zram, index) : 0;
mem = kmap_atomic(page);
zram_fill_page(mem, PAGE_SIZE, value);
kunmap_atomic(mem);
Expand All @@ -1297,7 +1324,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
if (size != PAGE_SIZE)
zstrm = zcomp_stream_get(zram->comp);

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);
Expand All @@ -1309,7 +1336,7 @@ static int __zram_bvec_read(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. */
Expand Down Expand Up @@ -1357,7 +1384,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
{
int ret = 0;
unsigned long alloced_pages;
unsigned long handle = 0;
struct zram_entry *entry = NULL;
unsigned int comp_len = 0;
void *src, *dst, *mem;
struct zcomp_strm *zstrm;
Expand All @@ -1384,38 +1411,39 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
if (unlikely(ret)) {
zcomp_stream_put(zram->comp);
pr_err("Compression failed! err=%d\n", ret);
zs_free(zram->mem_pool, handle);
if (entry)
zram_entry_free(zram, entry);
return ret;
}

if (comp_len >= huge_class_size)
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);
if (handle)
if (entry)
goto compress_again;
return -ENOMEM;
}
Expand All @@ -1425,11 +1453,11 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,

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

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)
Expand All @@ -1439,7 +1467,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
kunmap_atomic(src);

zcomp_stream_put(zram->comp);
zs_unmap_object(zram->mem_pool, handle);
zs_unmap_object(zram->mem_pool, entry->handle);
atomic64_add(comp_len, &zram->stats.compr_data_size);
out:
/*
Expand All @@ -1459,7 +1487,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
zram_set_flag(zram, index, flags);
zram_set_element(zram, index, element);
} else {
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);
Expand Down
6 changes: 5 additions & 1 deletion drivers/block/zram/zram_drv.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,14 @@ 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 flags;
Expand Down

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