linux-kernel - [PATCH -next] md: don't wait for MD_RECOVERY_NEEDED for HOT_REMOVE

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Message-Id: <20240627112321.3044744-1-yukuai1@huaweicloud.com>
Date: Thu, 27 Jun 2024 19:23:21 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: song@...nel.org,
	mateusz.kusiak@...ux.intel.com,
	mariusz.tkaczyk@...ux.intel.com,
	nfbrown@...e.de,
	hare@...e.de
Cc: linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH -next] md: don't wait for MD_RECOVERY_NEEDED for HOT_REMOVE_DISK ioctl

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

Commit 90f5f7ad4f38 ("md: Wait for md_check_recovery before attempting
device removal.") explained in the commit message that failed device
must be reomoved from the personality first by md_check_recovery(),
before it can be removed from the array. That's the reason the commit
add the code to wait for MD_RECOVERY_NEEDED.

However, this is not the case now, because remove_and_add_spares() is
called directly from hot_remove_disk() from ioctl path, hence failed
device(marked faulty) can be removed from the personality by ioctl.

On the other hand, the commit introduced a performance problem that
if MD_RECOVERY_NEEDED is set and the array is not running, ioctl will
wait for 5s before it can return failure to user.

Since the waiting is not needed now, fix the problem by removing the
waiting.

Fixes: 90f5f7ad4f38 ("md: Wait for md_check_recovery before attempting device removal.")
Reported-by: Mateusz Kusiak <mateusz.kusiak@...ux.intel.com>
Closes: https://lore.kernel.org/all/814ff6ee-47a2-4ba0-963e-cf256ee4ecfa@linux.intel.com/
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/md/md.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c0426a6d2fd1..da3065a3c2fb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7827,12 +7827,6 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
 		return get_bitmap_file(mddev, argp);
 	}

-	if (cmd == HOT_REMOVE_DISK)
-		/* need to ensure recovery thread has run */
-		wait_event_interruptible_timeout(mddev->sb_wait,
-						 !test_bit(MD_RECOVERY_NEEDED,
-							   &mddev->recovery),
-						 msecs_to_jiffies(5000));
 	if (cmd == STOP_ARRAY || cmd == STOP_ARRAY_RO) {
 		/* Need to flush page cache, and ensure no-one else opens
 		 * and writes
-- 
2.39.2