Commit 43c9835b authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: don't allow enabling a cache on devices that don't support it 



Currently the write_cache attribute allows enabling the QUEUE_FLAG_WC
flag on devices that never claimed the capability.

Fix that by adding a QUEUE_FLAG_HW_WC flag that is set by
blk_queue_write_cache and guards re-enabling the cache through sysfs.

Note that any rescan that calls blk_queue_write_cache will still
re-enable the write cache as in the current code.

Fixes: 93e9d8e8 ("block: add ability to flag write back caching on a device")
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230707094239.107968-3-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c4e21bcd

block/blk-settings.c

+5 −2
Original line number Diff line number Diff line
@@ -830,10 +830,13 @@ EXPORT_SYMBOL(blk_set_queue_depth); 
 */

void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)

{

	if (wc)

	if (wc) {

		blk_queue_flag_set(QUEUE_FLAG_HW_WC, q);

		blk_queue_flag_set(QUEUE_FLAG_WC, q);

	else

	} else {

		blk_queue_flag_clear(QUEUE_FLAG_HW_WC, q);

		blk_queue_flag_clear(QUEUE_FLAG_WC, q);

	}

	if (fua)

		blk_queue_flag_set(QUEUE_FLAG_FUA, q);

	else

block/blk-sysfs.c

+7 −4
Original line number Diff line number Diff line
@@ -449,13 +449,16 @@ static ssize_t queue_wc_show(struct request_queue *q, char *page) 
static ssize_t queue_wc_store(struct request_queue *q, const char *page,

			      size_t count)

{

	if (!strncmp(page, "write back", 10))

	if (!strncmp(page, "write back", 10)) {

		if (!test_bit(QUEUE_FLAG_HW_WC, &q->queue_flags))

			return -EINVAL;

		blk_queue_flag_set(QUEUE_FLAG_WC, q);

	else if (!strncmp(page, "write through", 13) ||

		 !strncmp(page, "none", 4))

	} else if (!strncmp(page, "write through", 13) ||

		 !strncmp(page, "none", 4)) {

		blk_queue_flag_clear(QUEUE_FLAG_WC, q);

	else

	} else {

		return -EINVAL;

	}



	return count;

}

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -538,6 +538,7 @@ struct request_queue { 
#define QUEUE_FLAG_ADD_RANDOM	10	/* Contributes to random pool */

#define QUEUE_FLAG_SYNCHRONOUS	11	/* always completes in submit context */

#define QUEUE_FLAG_SAME_FORCE	12	/* force complete on same CPU */

#define QUEUE_FLAG_HW_WC	18	/* Write back caching supported */

#define QUEUE_FLAG_INIT_DONE	14	/* queue is initialized */

#define QUEUE_FLAG_STABLE_WRITES 15	/* don't modify blks until WB is done */

#define QUEUE_FLAG_POLL		16	/* IO polling enabled if set */