We waste sizeof(swp_entry_t) for zswap header when using zsmalloc
as zpool driver because zsmalloc doesn't support eviction.
Add zpool_evictable() to detect if zpool is potentially evictable,
and use it in zswap to avoid waste memory for zswap header.
Signed-off-by: Yu Zhao <yuz...@google.com>
---
include/linux/zpool.h | 2 ++
mm/zpool.c | 26 ++++++++++++++++++++++++--
mm/zsmalloc.c | 7 -------
mm/zswap.c | 20 ++++++++++----------
4 files changed, 36 insertions(+), 19 deletions(-)
diff --git a/include/linux/zpool.h b/include/linux/zpool.h
index 004ba807df96..7238865e75b0 100644
--- a/include/linux/zpool.h
+++ b/include/linux/zpool.h
@@ -108,4 +108,6 @@ void zpool_register_driver(struct zpool_driver *driver);
int zpool_unregister_driver(struct zpool_driver *driver);
+bool zpool_evictable(struct zpool *pool);
+
#endif
diff --git a/mm/zpool.c b/mm/zpool.c
index fd3ff719c32c..ec63ef32d73d 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -21,6 +21,7 @@ struct zpool {
struct zpool_driver *driver;
void *pool;
const struct zpool_ops *ops;
+ bool evictable;
struct list_head list;
};
@@ -142,7 +143,7 @@ EXPORT_SYMBOL(zpool_has_pool);
*
* This creates a new zpool of the specified type. The gfp flags will be
* used when allocating memory, if the implementation supports it. If the
- * ops param is NULL, then the created zpool will not be shrinkable.
+ * ops param is NULL, then the created zpool will not be evictable.
*
* Implementations must guarantee this to be thread-safe.
*
@@ -180,6 +181,8 @@ struct zpool *zpool_create_pool(const char *type, const
char *name, gfp_t gfp,
zpool->driver = driver;
zpool->pool = driver->create(name, gfp, ops, zpool);
zpool->ops = ops;
+ zpool->evictable = zpool->driver->shrink &&
+ zpool->ops && zpool->ops->evict;
if (!zpool->pool) {
pr_err("couldn't create %s pool\n", type);
@@ -296,7 +299,8 @@ void zpool_free(struct zpool *zpool, unsigned long handle)
int zpool_shrink(struct zpool *zpool, unsigned int pages,
unsigned int *reclaimed)
{
- return zpool->driver->shrink(zpool->pool, pages, reclaimed);
+ return zpool->driver->shrink ?
+ zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
}
/**
@@ -355,6 +359,24 @@ u64 zpool_get_total_size(struct zpool *zpool)
return zpool->driver->total_size(zpool->pool);
}
+/**
+ * zpool_evictable() - Test if zpool is potentially evictable
+ * @pool The zpool to test
+ *
+ * Zpool is only potentially evictable when it's created with struct
+ * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
+ *
+ * However, it doesn't necessarily mean driver will use zpool_ops.evict
+ * in its implementation of zpool_driver.shrink. It could do internal
+ * defragmentation instead.
+ *
+ * Returns: true if potentially evictable; false otherwise.
+ */
+bool zpool_evictable(struct zpool *zpool)
+{
+ return zpool->evictable;
+}
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dan Streetman <ddstr...@ieee.org>");
MODULE_DESCRIPTION("Common API for compressed memory storage");
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 683c0651098c..9cc741bcdb32 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -407,12 +407,6 @@ static void zs_zpool_free(void *pool, unsigned long handle)
zs_free(pool, handle);
}
-static int zs_zpool_shrink(void *pool, unsigned int pages,
- unsigned int *reclaimed)
-{
- return -EINVAL;
-}
-
static void *zs_zpool_map(void *pool, unsigned long handle,
enum zpool_mapmode mm)
{
@@ -450,7 +444,6 @@ static struct zpool_driver zs_zpool_driver = {
.destroy = zs_zpool_destroy,
.malloc = zs_zpool_malloc,
.free = zs_zpool_free,
- .shrink = zs_zpool_shrink,
.map = zs_zpool_map,
.unmap = zs_zpool_unmap,
.total_size = zs_zpool_total_size,
diff --git a/mm/zswap.c b/mm/zswap.c
index d39581a076c3..52a9ab519ab2 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -964,11 +964,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t
offset,
struct zswap_entry *entry, *dupentry;
struct crypto_comp *tfm;
int ret;
- unsigned int dlen = PAGE_SIZE, len;
+ unsigned int hlen, dlen = PAGE_SIZE;
unsigned long handle;
char *buf;
u8 *src, *dst;
- struct zswap_header *zhdr;
+ struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
if (!zswap_enabled || !tree) {
ret = -ENODEV;
@@ -1013,8 +1013,8 @@ static int zswap_frontswap_store(unsigned type, pgoff_t
offset,
}
/* store */
- len = dlen + sizeof(struct zswap_header);
- ret = zpool_malloc(entry->pool->zpool, len,
+ hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
+ ret = zpool_malloc(entry->pool->zpool, hlen + dlen,
__GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
&handle);
if (ret == -ENOSPC) {
@@ -1025,10 +1025,9 @@ static int zswap_frontswap_store(unsigned type, pgoff_t
offset,
zswap_reject_alloc_fail++;
goto put_dstmem;
}
- zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
- zhdr->swpentry = swp_entry(type, offset);
- buf = (u8 *)(zhdr + 1);
- memcpy(buf, dst, dlen);
+ buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
+ memcpy(buf, &zhdr, hlen);
+ memcpy(buf + hlen, dst, dlen);
zpool_unmap_handle(entry->pool->zpool, handle);
put_cpu_var(zswap_dstmem);
@@ -1091,8 +1090,9 @@ static int zswap_frontswap_load(unsigned type, pgoff_t
offset,
/* decompress */
dlen = PAGE_SIZE;
- src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
- ZPOOL_MM_RO) + sizeof(struct zswap_header);
+ src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
+ if (zpool_evictable(entry->pool->zpool))
+ src += sizeof(struct zswap_header);
dst = kmap_atomic(page);
tfm = *get_cpu_ptr(entry->pool->tfm);
ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
--
2.16.0.rc1.238.g530d649a79-goog
