linux-kernel - Re: [PATCHv4 00/10] add on-demand device creation

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Date:	Thu, 7 May 2015 09:33:22 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 00/10] add on-demand device creation

On (05/06/15 17:20), Minchan Kim wrote:
> I'm fine, too.
> 
> > 
> > 
> > 
> > can you please test this patch?
> 
> I tested it and couldn't reproduce it during 5 minutes so it seems
> we are correct about culpit.
> However, it's trick and we should find a right way. :)
> 

well, I can't reproduce this race.

btw, just for info. your script does

zram_add
dd &
zram_remove

by the time dd starts writing zramX device may be gone, so along with
block devices we can see regular files in /dev/

[..]
brw-rw---- 1 root disk   254, 0 May  7 09:16 /dev/zram0
-rw-r--r-- 1 root root 10485760 May  7 09:17 /dev/zram1
-rw-r--r-- 1 root root 10485760 May  7 09:20 /dev/zram10
[..]


can you please test thit patch?

---

 drivers/block/zram/zram_drv.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index e6c4316..1e99d9f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1278,6 +1278,8 @@ out_free_dev:
 static int zram_remove(struct zram *zram)
 {
 	struct block_device *bdev;
+	struct request_queue *q;
+	int device_id;
 
 	bdev = bdget_disk(zram->disk, 0);
 	if (!bdev)
@@ -1306,14 +1308,18 @@ static int zram_remove(struct zram *zram)
 	/* Make sure all the pending I/O are finished */
 	fsync_bdev(bdev);
 	zram_reset_device(zram);
-	bdput(bdev);
+
+	q = zram->disk->queue;
+	device_id = zram->disk->first_minor;
 
 	pr_info("Removed device: %s\n", zram->disk->disk_name);
 
-	idr_remove(&zram_index_idr, zram->disk->first_minor);
-	blk_cleanup_queue(zram->disk->queue);
 	del_gendisk(zram->disk);
 	put_disk(zram->disk);
+	blk_cleanup_queue(q);
+	bdput(bdev);
+
+	idr_remove(&zram_index_idr, device_id);
 	kfree(zram);
 	return 0;
 }
--
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