[merged mm-stable] zram-remove-second-stage-of-handle-allocation.patch removed from -mm tree

[merged mm-stable] zram-remove-second-stage-of-handle-allocation.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: zram: remove second stage of handle allocation
has been removed from the -mm tree.  Its filename was
     zram-remove-second-stage-of-handle-allocation.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: remove second stage of handle allocation
Date: Mon, 3 Mar 2025 11:03:14 +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) 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).

Link: https://lkml.kernel.org/r/20250303022425.285971-6-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |   39 +++++---------------------------
 1 file changed, 7 insertions(+), 32 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-remove-second-stage-of-handle-allocation
+++ a/drivers/block/zram/zram_drv.c
@@ -1723,11 +1723,11 @@ 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) */
@@ -1741,7 +1741,6 @@ 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,
@@ -1751,7 +1750,6 @@ compress_again:
 	if (unlikely(ret)) {
 		zcomp_stream_put(zstrm);
 		pr_err("Compression failed! err=%d\n", ret);
-		zs_free(zram->mem_pool, handle);
 		return ret;
 	}
 
@@ -1760,35 +1758,12 @@ 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.
-	 */
-	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_NOWARN |
+			   __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)) {
_

Patches currently in -mm which might be from senozhatsky@chromium.org are