linux-kernel - [PATCH RFC md-6.16 v3 08/19] md/md-bitmap: add a new helper blocks_synced() in bitmap

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Message-Id: <20250512011927.2809400-9-yukuai1@huaweicloud.com>
Date: Mon, 12 May 2025 09:19:16 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: hch@....de,
	xni@...hat.com,
	colyli@...nel.org,
	agk@...hat.com,
	snitzer@...nel.org,
	mpatocka@...hat.com,
	song@...nel.org,
	yukuai3@...wei.com
Cc: linux-kernel@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	linux-raid@...r.kernel.org,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH RFC md-6.16 v3 08/19] md/md-bitmap: add a new helper blocks_synced() in bitmap_operations

From: Yu Kuai <yukuai3@...wei.com>

Currently, raid456 must perform a whole array initial recovery to build
initail xor data, then IO to the array won't have to read all the blocks
in underlying disks.

This behavior will affect IO performance a lot, and nowadays there are
huge disks and the initial recovery can take a long time. Hence llbitmap
will support lazy initial recovery in following patches. This helper is
used to check if data blocks is synced or not, if not then IO will still
have to read all blocks.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/md/md-bitmap.h | 1 +
 drivers/md/raid5.c     | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
index 13be2a10801a..4e27f5f793b7 100644
--- a/drivers/md/md-bitmap.h
+++ b/drivers/md/md-bitmap.h
@@ -99,6 +99,7 @@ struct bitmap_operations {
 	void (*end_discard)(struct mddev *mddev, sector_t offset,
 			    unsigned long sectors);
 
+	bool (*blocks_synced)(struct mddev *mddev, sector_t offset);
 	sector_t (*skip_sync_blocks)(struct mddev *mddev, sector_t offset);
 	bool (*start_sync)(struct mddev *mddev, sector_t offset,
 			   sector_t *blocks, bool degraded);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 7e66a99f29af..e5d3d8facb4b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3748,6 +3748,7 @@ static int want_replace(struct stripe_head *sh, int disk_idx)
 static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
 			   int disk_idx, int disks)
 {
+	struct mddev *mddev = sh->raid_conf->mddev;
 	struct r5dev *dev = &sh->dev[disk_idx];
 	struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
 				  &sh->dev[s->failed_num[1]] };
@@ -3762,6 +3763,11 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
 		 */
 		return 0;
 
+	/* The initial recover is not done, must read everything */
+	if (mddev->bitmap_ops && mddev->bitmap_ops->blocks_synced &&
+	    !mddev->bitmap_ops->blocks_synced(mddev, sh->sector))
+		return 1;
+
 	if (dev->toread ||
 	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)))
 		/* We need this block to directly satisfy a request */
-- 
2.39.2