Skip to content

Commit

Permalink
zram: introduce zram_entry to prepare dedup functionality
Browse files Browse the repository at this point in the history 
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]>
[dereference23: remove __GFP_CMA]
Signed-off-by: Alexander Winkowski <[email protected]>
  • Loading branch information
@JoonsooKim @dereference23
JoonsooKim authored and dereference23 committed Feb 10, 2022
1 parent 4438239 commit c675182
Show file tree
Hide file tree
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 @@ -1169,6 +1170,32 @@ 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 @@ -1209,7 +1236,7 @@ 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 @@ -1238,17 +1265,17 @@ 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 @@ -1258,7 +1285,7 @@ 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 @@ -1277,12 +1304,12 @@ 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 @@ -1295,7 +1322,7 @@ 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 @@ -1307,7 +1334,7 @@ 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 @@ -1355,7 +1382,7 @@ 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 @@ -1382,38 +1409,39 @@ 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 @@ -1423,11 +1451,11 @@ 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 @@ -1437,7 +1465,7 @@ 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 @@ -1457,7 +1485,7 @@ 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

0 comments on commit c675182

Please sign in to comment.