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zram: remove second stage of handle allocation

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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>
This commit is contained in:
Sergey Senozhatsky 2025-03-03 11:03:14 +09:00 committed by Andrew Morton
parent 4127e13c93
commit 80af56cb29
1 changed files with 7 additions and 32 deletions
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39
drivers/block/zram/zram_drv.c
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@ -1723,11 +1723,11 @@ 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) */
@ -1741,7 +1741,6 @@ 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,
@ -1751,7 +1750,6 @@ 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;
}
@ -1760,35 +1758,12 @@ 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_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)) {