The patch titled
Subject: zram: remove two-staged handle allocation
has been added to the -mm mm-unstable branch. Its filename is
zram-remove-two-staged-handle-allocation.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-remove-two-staged-handle-allocation.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: remove two-staged handle allocation
Date: Mon, 27 Jan 2025 16:29:16 +0900
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) when the fast path
failed.
Since it's not atomic anymore we can permit direct reclaim during
allocation, and remove fast allocation path and, also, drop the
recompression path (which should reduce CPU/battery usage).
Link: https://lkml.kernel.org/r/20250127072932.1289973-6-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 41 ++++----------------------------
1 file changed, 6 insertions(+), 35 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-remove-two-staged-handle-allocation
+++ a/drivers/block/zram/zram_drv.c
@@ -1725,11 +1725,11 @@ static int write_incompressible_page(str
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) */
@@ -1743,7 +1743,6 @@ static int zram_write_page(struct zram *
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,
@@ -1752,8 +1751,6 @@ compress_again:
if (unlikely(ret)) {
zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP], zstrm);
- pr_err("Compression failed! err=%d\n", ret);
- zs_free(zram->mem_pool, handle);
return ret;
}
@@ -1762,36 +1759,10 @@ compress_again:
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.
- */
+ handle = zs_malloc(zram->mem_pool, comp_len,
+ GFP_NOIO | __GFP_HIGHMEM | __GFP_MOVABLE);
if (IS_ERR_VALUE(handle))
- handle = zs_malloc(zram->mem_pool, comp_len,
- __GFP_KSWAPD_RECLAIM |
- __GFP_NOWARN |
- __GFP_HIGHMEM |
- __GFP_MOVABLE);
- if (IS_ERR_VALUE(handle)) {
- zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP], 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)) {
zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP], zstrm);
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-switch-to-non-atomic-entry-locking.patch
zram-do-not-use-per-cpu-compression-streams.patch
zram-remove-crypto-include.patch
zram-remove-max_comp_streams-device-attr.patch
zram-remove-two-staged-handle-allocation.patch
zram-permit-reclaim-in-zstd-custom-allocator.patch
zram-permit-reclaim-in-recompression-handle-allocation.patch
zram-remove-writestall-zram_stats-member.patch
zram-unlock-slot-during-recompression.patch
