+ zram-use-zram_read_from_zspool-in-writeback.patch added to mm-unstable branch

+ zram-use-zram_read_from_zspool-in-writeback.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: zram: use zram_read_from_zspool() in writeback
has been added to the -mm mm-unstable branch.  Its filename is
     zram-use-zram_read_from_zspool-in-writeback.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-use-zram_read_from_zspool-in-writeback.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@chromium.org>
Subject: zram: use zram_read_from_zspool() in writeback
Date: Wed, 18 Dec 2024 15:34:23 +0900

We only can read pages from zspool in writeback, zram_read_page() is not
really right in that context not only because it's a more generic function
that handles ZRAM_WB pages, but also because it requires us to unlock slot
between slot flag check and actual page read.  Use zram_read_from_zspool()
instead and do slot flags check and page read under the same slot lock.

Link: https://lkml.kernel.org/r/20241218063513.297475-7-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-use-zram_read_from_zspool-in-writeback
+++ a/drivers/block/zram/zram_drv.c
@@ -55,8 +55,8 @@ static size_t huge_class_size;
 static const struct block_device_operations zram_devops;
 
 static void zram_free_page(struct zram *zram, size_t index);
-static int zram_read_page(struct zram *zram, struct page *page, u32 index,
-			  struct bio *parent);
+static int zram_read_from_zspool(struct zram *zram, struct page *page,
+				 u32 index);
 
 static int zram_slot_trylock(struct zram *zram, u32 index)
 {
@@ -831,13 +831,10 @@ static ssize_t writeback_store(struct de
 		 */
 		if (!zram_test_flag(zram, index, ZRAM_PP_SLOT))
 			goto next;
+		if (zram_read_from_zspool(zram, page, index))
+			goto next;
 		zram_slot_unlock(zram, index);
 
-		if (zram_read_page(zram, page, index, NULL)) {
-			release_pp_slot(zram, pps);
-			continue;
-		}
-
 		bio_init(&bio, zram->bdev, &bio_vec, 1,
 			 REQ_OP_WRITE | REQ_SYNC);
 		bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
_

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

zram-free-slot-memory-early-during-write.patch
zram-remove-entry-element-member.patch
zram-factor-out-zram_same-write.patch
zram-factor-out-zram_huge-write.patch
zram-factor-out-different-page-types-read.patch
zram-use-zram_read_from_zspool-in-writeback.patch
zram-cond_resched-in-writeback-loop.patch