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Commit b4c5c609 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
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zram: avoid lockdep splat by revalidate_disk 

Sasha reported lockdep warning [1] introduced by [2].

It could be fixed by doing disk revalidation out of the init_lock.  It's
okay because disk capacity change is protected by init_lock so that
revalidate_disk always sees up-to-date value so there is no race.

[1] https://lkml.org/lkml/2014/7/3/735


[2] zram: revalidate disk after capacity change

Fixes 2e32baea ("zram: revalidate disk after capacity change").

Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Reported-by: default avatarSasha Levin <sasha.levin@oracle.com>
Cc: "Alexander E. Patrakov" <patrakov@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
CC: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a0f7a756

drivers/block/zram/zram_drv.c

+18 −4
Original line number Diff line number Diff line
@@ -622,11 +622,18 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity) 
	memset(&zram->stats, 0, sizeof(zram->stats));



	zram->disksize = 0;

	if (reset_capacity) {

	if (reset_capacity)

		set_capacity(zram->disk, 0);

		revalidate_disk(zram->disk);

	}



	up_write(&zram->init_lock);



	/*

	 * Revalidate disk out of the init_lock to avoid lockdep splat.

	 * It's okay because disk's capacity is protected by init_lock

	 * so that revalidate_disk always sees up-to-date capacity.

	 */

	if (reset_capacity)

		revalidate_disk(zram->disk);

}



static ssize_t disksize_store(struct device *dev,
@@ -666,8 +673,15 @@ static ssize_t disksize_store(struct device *dev, 
	zram->comp = comp;

	zram->disksize = disksize;

	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);

	revalidate_disk(zram->disk);

	up_write(&zram->init_lock);



	/*

	 * Revalidate disk out of the init_lock to avoid lockdep splat.

	 * It's okay because disk's capacity is protected by init_lock

	 * so that revalidate_disk always sees up-to-date capacity.

	 */

	revalidate_disk(zram->disk);



	return len;



out_destroy_comp: