6.4-stable review patch. If anyone has any objections, please let me know.
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From: Christoph Hellwig hch@lst.de
[ Upstream commit 43c9835b144c7ce29efe142d662529662a9eb376 ]
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: 93e9d8e836cb ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-settings.c | 7 +++++-- block/blk-sysfs.c | 11 +++++++---- include/linux/blkdev.h | 1 + 3 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/block/blk-settings.c b/block/blk-settings.c index 4dd59059b788e..0046b447268f9 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -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 diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 50a0094300f2d..b7fc4cf3f992c 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -517,13 +517,16 @@ 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; } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 67e942d776bd8..2e2cd4b824e7f 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -546,6 +546,7 @@ 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 */