Previously zram write() was atomic which required us to pass
__GFP_KSWAPD_RECLAIM to zsmalloc handle allocation on a fast
path and attempt a slow path allocation (with recompression)
if the fast path failed.
Since we are not in atomic context anymore we can permit
direct reclaim during handle allocation, and hence can have
a single allocation path. There is no slow path anymore so
we don't unlock per-CPU stream (and don't lose compressed
data) which means that there is no need to do recompression
now (which should reduce CPU and battery usage).
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 38 ++++++-----------------------------
1 file changed, 6 insertions(+), 32 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index c7bc0c9f3f2f..4ccc1a1a8f20 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1729,11 +1729,11 @@ static int write_incompressible_page(struct zram *zram, struct page *page,
static int zram_write_page(struct zram *zram, struct page *page, u32 index)
{
int ret = 0;
- unsigned long handle = -ENOMEM;
- unsigned int comp_len = 0;
+ unsigned long handle;
+ unsigned int comp_len;
void *dst, *mem;
struct zcomp_strm *zstrm;
- unsigned long element = 0;
+ unsigned long element;
bool same_filled;
/* First, free memory allocated to this slot (if any) */
@@ -1747,7 +1747,6 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
if (same_filled)
return write_same_filled_page(zram, element, index);
-compress_again:
zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
mem = kmap_local_page(page);
ret = zcomp_compress(zram->comps[ZRAM_PRIMARY_COMP], zstrm,
@@ -1757,7 +1756,6 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
if (unlikely(ret)) {
zcomp_stream_put(zstrm);
pr_err("Compression failed! err=%d\n", ret);
- zs_free(zram->mem_pool, handle);
return ret;
}
@@ -1766,35 +1764,11 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
return write_incompressible_page(zram, page, index);
}
- /*
- * handle 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.
- *
- * if we have a 'non-null' handle here then we are coming
- * from the slow path and handle has already been allocated.
- */
- if (IS_ERR_VALUE(handle))
- handle = zs_malloc(zram->mem_pool, comp_len,
- __GFP_KSWAPD_RECLAIM |
- __GFP_NOWARN |
- __GFP_HIGHMEM |
- __GFP_MOVABLE);
+ handle = zs_malloc(zram->mem_pool, comp_len,
+ GFP_NOIO | __GFP_HIGHMEM | __GFP_MOVABLE);
if (IS_ERR_VALUE(handle)) {
zcomp_stream_put(zstrm);
- atomic64_inc(&zram->stats.writestall);
- handle = zs_malloc(zram->mem_pool, comp_len,
- GFP_NOIO | __GFP_HIGHMEM |
- __GFP_MOVABLE);
- if (IS_ERR_VALUE(handle))
- return PTR_ERR((void *)handle);
-
- goto compress_again;
+ return PTR_ERR((void *)handle);
}
if (!zram_can_store_page(zram)) {
--
2.48.1.601.g30ceb7b040-goog
