Commit a934a00a authored by Martin K. Petersen's avatar Martin K. Petersen Committed by Jens Axboe
Browse files

block: Fix discard topology stacking and reporting 



In some cases we would end up stacking discard_zeroes_data incorrectly.
Fix this by enabling the feature by default for stacking drivers and
clearing it for low-level drivers. Incorporating a device that does not
support dzd will then cause the feature to be disabled in the stacking
driver.

Also ensure that the maximum discard value does not overflow when
exported in sysfs and return 0 in the alignment and dzd fields for
devices that don't support discard.

Reported-by: default avatarLukas Czerner <lczerner@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent bbdd304c

block/blk-settings.c

+2 −1
Original line number Diff line number Diff line
@@ -120,7 +120,7 @@ void blk_set_default_limits(struct queue_limits *lim) 
	lim->discard_granularity = 0;

	lim->discard_alignment = 0;

	lim->discard_misaligned = 0;

	lim->discard_zeroes_data = -1;

	lim->discard_zeroes_data = 1;

	lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;

	lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);

	lim->alignment_offset = 0;
@@ -166,6 +166,7 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 


	blk_set_default_limits(&q->limits);

	blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);

	q->limits.discard_zeroes_data = 0;



	/*

	 * by default assume old behaviour and bounce for any highmem page

block/blk-sysfs.c

+2 −1
Original line number Diff line number Diff line
@@ -152,7 +152,8 @@ static ssize_t queue_discard_granularity_show(struct request_queue *q, char *pag 


static ssize_t queue_discard_max_show(struct request_queue *q, char *page)

{

	return queue_var_show(q->limits.max_discard_sectors << 9, page);

	return sprintf(page, "%llu\n",

		       (unsigned long long)q->limits.max_discard_sectors << 9);

}



static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)

include/linux/blkdev.h

+5 −2
Original line number Diff line number Diff line
@@ -257,7 +257,7 @@ struct queue_limits { 
	unsigned char		misaligned;

	unsigned char		discard_misaligned;

	unsigned char		cluster;

	signed char		discard_zeroes_data;

	unsigned char		discard_zeroes_data;

};



struct request_queue
@@ -1069,13 +1069,16 @@ static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector 
{

	unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);



	if (!lim->max_discard_sectors)

		return 0;



	return (lim->discard_granularity + lim->discard_alignment - alignment)

		& (lim->discard_granularity - 1);

}



static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)

{

	if (q->limits.discard_zeroes_data == 1)

	if (q->limits.max_discard_sectors && q->limits.discard_zeroes_data == 1)

		return 1;



	return 0;

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