linux-kernel - [PATCH 1/5] zram: move index preparation to a separate function in writeback

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230911133430.1824564-2-kernel@pankajraghav.com>
Date:   Mon, 11 Sep 2023 15:34:26 +0200
From:   Pankaj Raghav <kernel@...kajraghav.com>
To:     minchan@...nel.org, senozhatsky@...omium.org
Cc:     linux-kernel@...r.kernel.org, axboe@...nel.dk,
        p.raghav@...sung.com, linux-block@...r.kernel.org,
        kernel@...kajraghav.com, gost.dev@...sung.com
Subject: [PATCH 1/5] zram: move index preparation to a separate function in writeback_store

From: Pankaj Raghav <p.raghav@...sung.com>

Add a new function writeback_prep_or_skip_index() that does the check
and set the approapriate flags before writeback starts. The function
returns false if the index can be skipped.

Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
---
 drivers/block/zram/zram_drv.c | 68 +++++++++++++++++++++--------------
 1 file changed, 42 insertions(+), 26 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 06673c6ca255..eaf9e227778e 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -595,6 +595,46 @@ static void read_from_bdev_async(struct zram *zram, struct page *page,
 #define IDLE_WRITEBACK			(1<<1)
 #define INCOMPRESSIBLE_WRITEBACK	(1<<2)
 
+/*
+ * Returns: true if the index was prepared for further processing
+ *          false if the index can be skipped
+ */
+static bool writeback_prep_or_skip_index(struct zram *zram, int mode,
+					 unsigned long index)
+{
+	bool ret = false;
+
+	zram_slot_lock(zram, index);
+	if (!zram_allocated(zram, index))
+		goto skip;
+
+	if (zram_test_flag(zram, index, ZRAM_WB) ||
+	    zram_test_flag(zram, index, ZRAM_SAME) ||
+	    zram_test_flag(zram, index, ZRAM_UNDER_WB))
+		goto skip;
+
+	if (mode & IDLE_WRITEBACK && !zram_test_flag(zram, index, ZRAM_IDLE))
+		goto skip;
+	if (mode & HUGE_WRITEBACK && !zram_test_flag(zram, index, ZRAM_HUGE))
+		goto skip;
+	if (mode & INCOMPRESSIBLE_WRITEBACK &&
+	    !zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
+		goto skip;
+
+	/*
+	 * Clearing ZRAM_UNDER_WB is duty of caller.
+	 * IOW, zram_free_page never clear it.
+	 */
+	zram_set_flag(zram, index, ZRAM_UNDER_WB);
+	/* Need for hugepage writeback racing */
+	zram_set_flag(zram, index, ZRAM_IDLE);
+
+	ret = true;
+skip:
+	zram_slot_unlock(zram, index);
+	return ret;
+}
+
 static ssize_t writeback_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -662,33 +702,9 @@ static ssize_t writeback_store(struct device *dev,
 			}
 		}
 
-		zram_slot_lock(zram, index);
-		if (!zram_allocated(zram, index))
-			goto next;
+		if (!writeback_prep_or_skip_index(zram, mode, index))
+			continue;
 
-		if (zram_test_flag(zram, index, ZRAM_WB) ||
-				zram_test_flag(zram, index, ZRAM_SAME) ||
-				zram_test_flag(zram, index, ZRAM_UNDER_WB))
-			goto next;
-
-		if (mode & IDLE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_IDLE))
-			goto next;
-		if (mode & HUGE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_HUGE))
-			goto next;
-		if (mode & INCOMPRESSIBLE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
-			goto next;
-
-		/*
-		 * Clearing ZRAM_UNDER_WB is duty of caller.
-		 * IOW, zram_free_page never clear it.
-		 */
-		zram_set_flag(zram, index, ZRAM_UNDER_WB);
-		/* Need for hugepage writeback racing */
-		zram_set_flag(zram, index, ZRAM_IDLE);
-		zram_slot_unlock(zram, index);
 		if (zram_read_page(zram, page, index, NULL)) {
 			zram_slot_lock(zram, index);
 			zram_clear_flag(zram, index, ZRAM_UNDER_WB);
-- 
2.40.1