The patch titled
Subject: zswap: only save zswap header if zpool is shrinkable
has been added to the -mm tree. Its filename is
zswap-only-save-zswap-header-if-zpool-is-shrinkable.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zswap-only-save-zswap-header-if-zpool-is-shrinkable.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zswap-only-save-zswap-header-if-zpool-is-shrinkable.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
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------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: zswap: only save zswap header if zpool is shrinkable
We waste sizeof(swp_entry_t) for zswap header when using zsmalloc
as zpool driver because zsmalloc doesn't support eviction.
Add zpool_shrinkable() to detect if zpool is shrinkable, and use
it in zswap to avoid waste memory for zswap header.
Link: http://lkml.kernel.org/r/20180108225101.15790-1-yuzhao@xxxxxxxxxx
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/zpool.h | 2 ++
mm/zpool.c | 17 ++++++++++++++++-
mm/zsmalloc.c | 7 -------
mm/zswap.c | 16 ++++++++--------
4 files changed, 26 insertions(+), 16 deletions(-)
diff -puN include/linux/zpool.h~zswap-only-save-zswap-header-if-zpool-is-shrinkable include/linux/zpool.h
--- a/include/linux/zpool.h~zswap-only-save-zswap-header-if-zpool-is-shrinkable
+++ a/include/linux/zpool.h
@@ -108,4 +108,6 @@ void zpool_register_driver(struct zpool_
int zpool_unregister_driver(struct zpool_driver *driver);
+bool zpool_shrinkable(struct zpool *pool);
+
#endif
diff -puN mm/zpool.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable mm/zpool.c
--- a/mm/zpool.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable
+++ a/mm/zpool.c
@@ -296,7 +296,8 @@ void zpool_free(struct zpool *zpool, uns
int zpool_shrink(struct zpool *zpool, unsigned int pages,
unsigned int *reclaimed)
{
- return zpool->driver->shrink(zpool->pool, pages, reclaimed);
+ return zpool_shrinkable(zpool) ?
+ zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
}
/**
@@ -355,6 +356,20 @@ u64 zpool_get_total_size(struct zpool *z
return zpool->driver->total_size(zpool->pool);
}
+/**
+ * zpool_shrinkable() - Test if zpool is shrinkable
+ * @pool The zpool to test
+ *
+ * Zpool is only shrinkable when it's created with struct
+ * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
+ *
+ * Returns: true if shrinkable; false otherwise.
+ */
+bool zpool_shrinkable(struct zpool *zpool)
+{
+ return zpool->ops && zpool->ops->evict && zpool->driver->shrink;
+}
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dan Streetman <ddstreet@xxxxxxxx>");
MODULE_DESCRIPTION("Common API for compressed memory storage");
diff -puN mm/zsmalloc.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable mm/zsmalloc.c
--- a/mm/zsmalloc.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable
+++ a/mm/zsmalloc.c
@@ -404,12 +404,6 @@ static void zs_zpool_free(void *pool, un
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)
{
@@ -447,7 +441,6 @@ static struct zpool_driver zs_zpool_driv
.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 -puN mm/zswap.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable mm/zswap.c
--- a/mm/zswap.c~zswap-only-save-zswap-header-if-zpool-is-shrinkable
+++ a/mm/zswap.c
@@ -1063,8 +1063,8 @@ static int zswap_frontswap_store(unsigne
}
/* store */
- len = dlen + sizeof(struct zswap_header);
- ret = zpool_malloc(entry->pool->zpool, len,
+ hlen = zpool_shrinkable(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) {
@@ -1075,10 +1075,9 @@ static int zswap_frontswap_store(unsigne
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);
@@ -1149,8 +1148,9 @@ static int zswap_frontswap_load(unsigned
/* 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_shrinkable(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);
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-dont-expose-page-to-fast-gup-before-its-ready.patch
zswap-only-save-zswap-header-if-zpool-is-shrinkable.patch
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