| Message ID | 1459350477-16404-6-git-send-email-axboe@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Mar 30, 2016 at 09:07:53AM -0600, Jens Axboe wrote: > Add an internal helper and flag for setting whether a queue has > write back caching, or write through (or none). Add a sysfs file > to show this as well, and make it changeable from user space. As per previous discussion: I don't really care about the way how we tell the block layer we have a writeback cache, but a NAK to having each driver call two interfaces to convey the same information. Please just look at q->flush_flag & REQ_FLUSH for now, and then improvem the interface if you don't like it (I don't particularly like it, but not to the point that I'm motivated enough to fix it :)) -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 03/30/2016 09:42 AM, Christoph Hellwig wrote: > On Wed, Mar 30, 2016 at 09:07:53AM -0600, Jens Axboe wrote: >> Add an internal helper and flag for setting whether a queue has >> write back caching, or write through (or none). Add a sysfs file >> to show this as well, and make it changeable from user space. > > As per previous discussion: I don't really care about the way how we > tell the block layer we have a writeback cache, but a NAK to having > each driver call two interfaces to convey the same information. > > Please just look at q->flush_flag & REQ_FLUSH for now, and then > improvem the interface if you don't like it (I don't particularly like > it, but not to the point that I'm motivated enough to fix it :)) That's fine, I don't mind making that change, just didn't do it for this version. I prefer if we change the cache flagging to be the primary way to signal it, it's more intuitive than REQ_FLUSH. It'll be in the next version.
On 03/30/2016 09:46 AM, Jens Axboe wrote: > On 03/30/2016 09:42 AM, Christoph Hellwig wrote: >> On Wed, Mar 30, 2016 at 09:07:53AM -0600, Jens Axboe wrote: >>> Add an internal helper and flag for setting whether a queue has >>> write back caching, or write through (or none). Add a sysfs file >>> to show this as well, and make it changeable from user space. >> >> As per previous discussion: I don't really care about the way how we >> tell the block layer we have a writeback cache, but a NAK to having >> each driver call two interfaces to convey the same information. >> >> Please just look at q->flush_flag & REQ_FLUSH for now, and then >> improvem the interface if you don't like it (I don't particularly like >> it, but not to the point that I'm motivated enough to fix it :)) > > That's fine, I don't mind making that change, just didn't do it for this > version. I prefer if we change the cache flagging to be the primary way > to signal it, it's more intuitive than REQ_FLUSH. > > It'll be in the next version. Conversion series in here now: http://git.kernel.dk/cgit/linux-block/log/?h=wb-buf-throttle
On Wed, Mar 30, 2016 at 10:23:50AM -0600, Jens Axboe wrote: > Conversion series in here now: > > http://git.kernel.dk/cgit/linux-block/log/?h=wb-buf-throttle The new API looks reasonable to me. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/block/blk-settings.c b/block/blk-settings.c index c7bb666aafd1..4dbd511a9889 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -846,6 +846,17 @@ void blk_queue_flush_queueable(struct request_queue *q, bool queueable) } EXPORT_SYMBOL_GPL(blk_queue_flush_queueable); +void blk_queue_write_cache(struct request_queue *q, bool enabled) +{ + spin_lock_irq(q->queue_lock); + if (enabled) + queue_flag_set(QUEUE_FLAG_WC, q); + else + queue_flag_clear(QUEUE_FLAG_WC, q); + spin_unlock_irq(q->queue_lock); +} +EXPORT_SYMBOL_GPL(blk_queue_write_cache); + static int __init blk_settings_init(void) { blk_max_low_pfn = max_low_pfn - 1; diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index dd93763057ce..954e510452d7 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -347,6 +347,38 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page, return ret; } +static ssize_t queue_wc_show(struct request_queue *q, char *page) +{ + if (test_bit(QUEUE_FLAG_WC, &q->queue_flags)) + return sprintf(page, "write back\n"); + + return sprintf(page, "write through\n"); +} + +static ssize_t queue_wc_store(struct request_queue *q, const char *page, + size_t count) +{ + int set = -1; + + if (!strncmp(page, "write back", 10)) + set = 1; + else if (!strncmp(page, "write through", 13) || + !strncmp(page, "none", 4)) + set = 0; + + if (set == -1) + return -EINVAL; + + spin_lock_irq(q->queue_lock); + if (set) + queue_flag_set(QUEUE_FLAG_WC, q); + else + queue_flag_clear(QUEUE_FLAG_WC, q); + spin_unlock_irq(q->queue_lock); + + return count; +} + static struct queue_sysfs_entry queue_requests_entry = { .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR }, .show = queue_requests_show, @@ -478,6 +510,12 @@ static struct queue_sysfs_entry queue_poll_entry = { .store = queue_poll_store, }; +static struct queue_sysfs_entry queue_wc_entry = { + .attr = {.name = "write_cache", .mode = S_IRUGO | S_IWUSR }, + .show = queue_wc_show, + .store = queue_wc_store, +}; + static struct attribute *default_attrs[] = { &queue_requests_entry.attr, &queue_ra_entry.attr, @@ -503,6 +541,7 @@ static struct attribute *default_attrs[] = { &queue_iostats_entry.attr, &queue_random_entry.attr, &queue_poll_entry.attr, + &queue_wc_entry.attr, NULL, }; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 7e5d7e018bea..76e875159e52 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -491,15 +491,18 @@ struct request_queue { #define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */ #define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/ #define QUEUE_FLAG_POLL 22 /* IO polling enabled if set */ +#define QUEUE_FLAG_WC 23 /* Write back caching */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ (1 << QUEUE_FLAG_SAME_COMP) | \ + (1 << QUEUE_FLAG_WC) | \ (1 << QUEUE_FLAG_ADD_RANDOM)) #define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ (1 << QUEUE_FLAG_SAME_COMP) | \ + (1 << QUEUE_FLAG_WC) | \ (1 << QUEUE_FLAG_POLL)) static inline void queue_lockdep_assert_held(struct request_queue *q) @@ -1009,6 +1012,7 @@ extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *); extern void blk_queue_rq_timeout(struct request_queue *, unsigned int); extern void blk_queue_flush(struct request_queue *q, unsigned int flush); extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable); +extern void blk_queue_write_cache(struct request_queue *q, bool enabled); extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev); extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
Add an internal helper and flag for setting whether a queue has write back caching, or write through (or none). Add a sysfs file to show this as well, and make it changeable from user space. Signed-off-by: Jens Axboe <axboe@fb.com> --- block/blk-settings.c | 11 +++++++++++ block/blk-sysfs.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/blkdev.h | 4 ++++ 3 files changed, 54 insertions(+)