linux-kernel - Re: [PATCH -next RFC 3/3] block: fix scan partition for exclusively open device again

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Date:   Thu, 16 Feb 2023 14:19:34 +0100
From:   Jan Kara <jack@...e.cz>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     hch@...radead.org, jack@...e.cz, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next RFC 3/3] block: fix scan partition for exclusively
 open device again

On Sun 12-02-23 17:26:41, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> As explained in commit 36369f46e917 ("block: Do not reread partition table
> on exclusively open device"), reread partition on the device that is
> exclusively opened by someone else is problematic.
> 
> This patch will make sure partition scan will only be proceed if current
> thread open the device exclusively, or the device is not opened
> exclusively, and in the later case, other scanners and exclusive openers
> will be blocked temporarily until partition scan is done.
> 
> Fixes: 10c70d95c0f2 ("block: remove the bd_openers checks in blk_drop_partitions")
> Cc: <stable@...r.kernel.org>
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Just one nit below.

> diff --git a/block/genhd.c b/block/genhd.c
> index c0d1220bd798..6ec10ffeb9cc 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -359,6 +359,7 @@ EXPORT_SYMBOL_GPL(disk_uevent);
>  int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
>  {
>  	struct block_device *bdev;
> +	int ret = 0;
>  
>  	if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
>  		return -EINVAL;
> @@ -367,11 +368,29 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
>  	if (disk->open_partitions)
>  		return -EBUSY;
>  
> -	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
> -	if (IS_ERR(bdev))
> -		return PTR_ERR(bdev);
> +	/*
> +	 * If the device is opened exclusively by current thread already, it's
> +	 * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
> +	 * synchronize with other exclusivet openers and other partition
				  ^^^ typo here

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR