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

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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: 93e9d8e836 ("block: add ability to flag write back caching on a device")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230707094239.107968-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2023-07-07 11:42:39 +02:00 committed by Jens Axboe
parent c4e21bcd0f
commit 43c9835b14
3 changed files with 13 additions and 6 deletions
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7
block/blk-settings.c
View File

@ -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

11
block/blk-sysfs.c
View File

@ -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;
}

1
include/linux/blkdev.h
View File

@ -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 */