On 08/12/2010 05:41 AM, Tejun Heo wrote:
> Barrier is deemed too heavy and will soon be replaced by FLUSH/FUA
> requests. Deprecate barrier. All REQ_HARDBARRIERs are failed with
> -EOPNOTSUPP and blk_queue_ordered() is replaced with simpler
> blk_queue_flush().
>
> blk_queue_flush() takes combinations of REQ_FLUSH and FUA. If a
> device has write cache and can flush it, it should set REQ_FLUSH. If
> the device can handle FUA writes, it should also set REQ_FUA.
Christoph, do these two patches (parts 2 and 3) make xen-blkfront
correct WRT barriers/flushing as far as your concerned?
Thanks,
J
> All blk_queue_ordered() users are converted.
>
> * ORDERED_DRAIN is mapped to 0 which is the default value.
> * ORDERED_DRAIN_FLUSH is mapped to REQ_FLUSH.
> * ORDERED_DRAIN_FLUSH_FUA is mapped to REQ_FLUSH | REQ_FUA.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Nick Piggin <npiggin@xxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
> Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
> Cc: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
> Cc: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
> Cc: Geert Uytterhoeven <Geert.Uytterhoeven@xxxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Alasdair G Kergon <agk@xxxxxxxxxx>
> Cc: Pierre Ossman <drzeus@xxxxxxxxx>
> Cc: Stefan Weinhuber <wein@xxxxxxxxxx>
> ---
> block/blk-barrier.c | 29 ----------------------------
> block/blk-core.c | 6 +++-
> block/blk-settings.c | 20 +++++++++++++++++++
> drivers/block/brd.c | 1 -
> drivers/block/loop.c | 2 +-
> drivers/block/osdblk.c | 2 +-
> drivers/block/ps3disk.c | 2 +-
> drivers/block/virtio_blk.c | 25 ++++++++---------------
> drivers/block/xen-blkfront.c | 43 +++++++++++------------------------------
> drivers/ide/ide-disk.c | 13 +++++------
> drivers/md/dm.c | 2 +-
> drivers/mmc/card/queue.c | 1 -
> drivers/s390/block/dasd.c | 1 -
> drivers/scsi/sd.c | 16 +++++++-------
> include/linux/blkdev.h | 6 +++-
> 15 files changed, 67 insertions(+), 102 deletions(-)
>
> diff --git a/block/blk-barrier.c b/block/blk-barrier.c
> index c807e9c..ed0aba5 100644
> --- a/block/blk-barrier.c
> +++ b/block/blk-barrier.c
> @@ -9,35 +9,6 @@
>
> #include "blk.h"
>
> -/**
> - * blk_queue_ordered - does this queue support ordered writes
> - * @q: the request queue
> - * @ordered: one of QUEUE_ORDERED_*
> - *
> - * Description:
> - * For journalled file systems, doing ordered writes on a commit
> - * block instead of explicitly doing wait_on_buffer (which is bad
> - * for performance) can be a big win. Block drivers supporting this
> - * feature should call this function and indicate so.
> - *
> - **/
> -int blk_queue_ordered(struct request_queue *q, unsigned ordered)
> -{
> - if (ordered != QUEUE_ORDERED_NONE &&
> - ordered != QUEUE_ORDERED_DRAIN &&
> - ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
> - ordered != QUEUE_ORDERED_DRAIN_FUA) {
> - printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
> - return -EINVAL;
> - }
> -
> - q->ordered = ordered;
> - q->next_ordered = ordered;
> -
> - return 0;
> -}
> -EXPORT_SYMBOL(blk_queue_ordered);
> -
> /*
> * Cache flushing for ordered writes handling
> */
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 5ab3ac2..3f802dd 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1203,11 +1203,13 @@ static int __make_request(struct request_queue *q, struct bio *bio)
> const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK;
> int rw_flags;
>
> - if ((bio->bi_rw & REQ_HARDBARRIER) &&
> - (q->next_ordered == QUEUE_ORDERED_NONE)) {
> + /* REQ_HARDBARRIER is no more */
> + if (WARN_ONCE(bio->bi_rw & REQ_HARDBARRIER,
> + "block: HARDBARRIER is deprecated, use FLUSH/FUA instead\n")) {
> bio_endio(bio, -EOPNOTSUPP);
> return 0;
> }
> +
> /*
> * low level driver can indicate that it wants pages above a
> * certain limit bounced to low memory (ie for highmem, or even
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index a234f4b..9b18afc 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -794,6 +794,26 @@ void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
> }
> EXPORT_SYMBOL(blk_queue_update_dma_alignment);
>
> +/**
> + * blk_queue_flush - configure queue's cache flush capability
> + * @q: the request queue for the device
> + * @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
> + *
> + * Tell block layer cache flush capability of @q. If it supports
> + * flushing, REQ_FLUSH should be set. If it supports bypassing
> + * write cache for individual writes, REQ_FUA should be set.
> + */
> +void blk_queue_flush(struct request_queue *q, unsigned int flush)
> +{
> + WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
> +
> + if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
> + flush &= ~REQ_FUA;
> +
> + q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
> +}
> +EXPORT_SYMBOL_GPL(blk_queue_flush);
> +
> static int __init blk_settings_init(void)
> {
> blk_max_low_pfn = max_low_pfn - 1;
> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
> index 47a4127..fa33f97 100644
> --- a/drivers/block/brd.c
> +++ b/drivers/block/brd.c
> @@ -482,7 +482,6 @@ static struct brd_device *brd_alloc(int i)
> if (!brd->brd_queue)
> goto out_free_dev;
> blk_queue_make_request(brd->brd_queue, brd_make_request);
> - blk_queue_ordered(brd->brd_queue, QUEUE_ORDERED_DRAIN);
> blk_queue_max_hw_sectors(brd->brd_queue, 1024);
> blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index c3a4a2e..953d1e1 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -832,7 +832,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
> lo->lo_queue->unplug_fn = loop_unplug;
>
> if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
> - blk_queue_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN_FLUSH);
> + blk_queue_flush(lo->lo_queue, REQ_FLUSH);
>
> set_capacity(lo->lo_disk, size);
> bd_set_size(bdev, size << 9);
> diff --git a/drivers/block/osdblk.c b/drivers/block/osdblk.c
> index 2284b4f..72d6246 100644
> --- a/drivers/block/osdblk.c
> +++ b/drivers/block/osdblk.c
> @@ -439,7 +439,7 @@ static int osdblk_init_disk(struct osdblk_device *osdev)
> blk_queue_stack_limits(q, osd_request_queue(osdev->osd));
>
> blk_queue_prep_rq(q, blk_queue_start_tag);
> - blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH);
> + blk_queue_flush(q, REQ_FLUSH);
>
> disk->queue = q;
>
> diff --git a/drivers/block/ps3disk.c b/drivers/block/ps3disk.c
> index e9da874..4911f9e 100644
> --- a/drivers/block/ps3disk.c
> +++ b/drivers/block/ps3disk.c
> @@ -468,7 +468,7 @@ static int __devinit ps3disk_probe(struct ps3_system_bus_device *_dev)
> blk_queue_dma_alignment(queue, dev->blk_size-1);
> blk_queue_logical_block_size(queue, dev->blk_size);
>
> - blk_queue_ordered(queue, QUEUE_ORDERED_DRAIN_FLUSH);
> + blk_queue_flush(queue, REQ_FLUSH);
>
> blk_queue_max_segments(queue, -1);
> blk_queue_max_segment_size(queue, dev->bounce_size);
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 7965280..d10b635 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -388,22 +388,15 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
> vblk->disk->driverfs_dev = &vdev->dev;
> index++;
>
> - if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH)) {
> - /*
> - * If the FLUSH feature is supported we do have support for
> - * flushing a volatile write cache on the host. Use that
> - * to implement write barrier support.
> - */
> - blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH);
> - } else {
> - /*
> - * If the FLUSH feature is not supported we must assume that
> - * the host does not perform any kind of volatile write
> - * caching. We still need to drain the queue to provider
> - * proper barrier semantics.
> - */
> - blk_queue_ordered(q, QUEUE_ORDERED_DRAIN);
> - }
> + /*
> + * If the FLUSH feature is supported we do have support for
> + * flushing a volatile write cache on the host. Use that to
> + * implement write barrier support; otherwise, we must assume
> + * that the host does not perform any kind of volatile write
> + * caching.
> + */
> + if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
> + blk_queue_flush(q, REQ_FLUSH);
>
> /* If disk is read-only in the host, the guest should obey */
> if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 25ffbf9..1d48f3a 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -95,7 +95,7 @@ struct blkfront_info
> struct gnttab_free_callback callback;
> struct blk_shadow shadow[BLK_RING_SIZE];
> unsigned long shadow_free;
> - int feature_barrier;
> + unsigned int feature_flush;
> int is_ready;
> };
>
> @@ -418,25 +418,12 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
> }
>
>
> -static int xlvbd_barrier(struct blkfront_info *info)
> +static void xlvbd_flush(struct blkfront_info *info)
> {
> - int err;
> - const char *barrier;
> -
> - switch (info->feature_barrier) {
> - case QUEUE_ORDERED_DRAIN: barrier = "enabled"; break;
> - case QUEUE_ORDERED_NONE: barrier = "disabled"; break;
> - default: return -EINVAL;
> - }
> -
> - err = blk_queue_ordered(info->rq, info->feature_barrier);
> -
> - if (err)
> - return err;
> -
> + blk_queue_flush(info->rq, info->feature_flush);
> printk(KERN_INFO "blkfront: %s: barriers %s\n",
> - info->gd->disk_name, barrier);
> - return 0;
> + info->gd->disk_name,
> + info->feature_flush ? "enabled" : "disabled");
> }
>
>
> @@ -515,7 +502,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
> info->rq = gd->queue;
> info->gd = gd;
>
> - xlvbd_barrier(info);
> + xlvbd_flush(info);
>
> if (vdisk_info & VDISK_READONLY)
> set_disk_ro(gd, 1);
> @@ -661,8 +648,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
> printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",
> info->gd->disk_name);
> error = -EOPNOTSUPP;
> - info->feature_barrier = QUEUE_ORDERED_NONE;
> - xlvbd_barrier(info);
> + info->feature_flush = 0;
> + xlvbd_flush(info);
> }
> /* fall through */
> case BLKIF_OP_READ:
> @@ -1075,19 +1062,13 @@ static void blkfront_connect(struct blkfront_info *info)
> /*
> * If there's no "feature-barrier" defined, then it means
> * we're dealing with a very old backend which writes
> - * synchronously; draining will do what needs to get done.
> + * synchronously; nothing to do.
> *
> * If there are barriers, then we use flush.
> - *
> - * If barriers are not supported, then there's no much we can
> - * do, so just set ordering to NONE.
> */
> - if (err)
> - info->feature_barrier = QUEUE_ORDERED_DRAIN;
> - else if (barrier)
> - info->feature_barrier = QUEUE_ORDERED_DRAIN_FLUSH;
> - else
> - info->feature_barrier = QUEUE_ORDERED_NONE;
> + info->feature_flush = 0;
> + if (!err && barrier)
> + info->feature_flush = REQ_FLUSH;
>
> err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
> if (err) {
> diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
> index 7433e07..7c5b01c 100644
> --- a/drivers/ide/ide-disk.c
> +++ b/drivers/ide/ide-disk.c
> @@ -516,10 +516,10 @@ static int ide_do_setfeature(ide_drive_t *drive, u8 feature, u8 nsect)
> return ide_no_data_taskfile(drive, &cmd);
> }
>
> -static void update_ordered(ide_drive_t *drive)
> +static void update_flush(ide_drive_t *drive)
> {
> u16 *id = drive->id;
> - unsigned ordered = QUEUE_ORDERED_NONE;
> + unsigned flush = 0;
>
> if (drive->dev_flags & IDE_DFLAG_WCACHE) {
> unsigned long long capacity;
> @@ -543,13 +543,12 @@ static void update_ordered(ide_drive_t *drive)
> drive->name, barrier ? "" : "not ");
>
> if (barrier) {
> - ordered = QUEUE_ORDERED_DRAIN_FLUSH;
> + flush = REQ_FLUSH;
> blk_queue_prep_rq(drive->queue, idedisk_prep_fn);
> }
> - } else
> - ordered = QUEUE_ORDERED_DRAIN;
> + }
>
> - blk_queue_ordered(drive->queue, ordered);
> + blk_queue_flush(drive->queue, flush);
> }
>
> ide_devset_get_flag(wcache, IDE_DFLAG_WCACHE);
> @@ -572,7 +571,7 @@ static int set_wcache(ide_drive_t *drive, int arg)
> }
> }
>
> - update_ordered(drive);
> + update_flush(drive);
>
> return err;
> }
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index a3f21dc..b71cc9e 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1908,7 +1908,7 @@ static struct mapped_device *alloc_dev(int minor)
> blk_queue_softirq_done(md->queue, dm_softirq_done);
> blk_queue_prep_rq(md->queue, dm_prep_fn);
> blk_queue_lld_busy(md->queue, dm_lld_busy);
> - blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH);
> + blk_queue_flush(md->queue, REQ_FLUSH);
>
> md->disk = alloc_disk(1);
> if (!md->disk)
> diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
> index c77eb49..d791772 100644
> --- a/drivers/mmc/card/queue.c
> +++ b/drivers/mmc/card/queue.c
> @@ -128,7 +128,6 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
> mq->req = NULL;
>
> blk_queue_prep_rq(mq->queue, mmc_prep_request);
> - blk_queue_ordered(mq->queue, QUEUE_ORDERED_DRAIN);
> queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mq->queue);
>
> #ifdef CONFIG_MMC_BLOCK_BOUNCE
> diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
> index 1a84fae..29046b7 100644
> --- a/drivers/s390/block/dasd.c
> +++ b/drivers/s390/block/dasd.c
> @@ -2197,7 +2197,6 @@ static void dasd_setup_queue(struct dasd_block *block)
> */
> blk_queue_max_segment_size(block->request_queue, PAGE_SIZE);
> blk_queue_segment_boundary(block->request_queue, PAGE_SIZE - 1);
> - blk_queue_ordered(block->request_queue, QUEUE_ORDERED_DRAIN);
> }
>
> /*
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 05a15b0..7f6aca2 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2109,7 +2109,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
> struct scsi_disk *sdkp = scsi_disk(disk);
> struct scsi_device *sdp = sdkp->device;
> unsigned char *buffer;
> - unsigned ordered;
> + unsigned flush = 0;
>
> SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,
> "sd_revalidate_disk\n"));
> @@ -2151,15 +2151,15 @@ static int sd_revalidate_disk(struct gendisk *disk)
>
> /*
> * We now have all cache related info, determine how we deal
> - * with ordered requests.
> + * with flush requests.
> */
> - if (sdkp->WCE)
> - ordered = sdkp->DPOFUA
> - ? QUEUE_ORDERED_DRAIN_FUA : QUEUE_ORDERED_DRAIN_FLUSH;
> - else
> - ordered = QUEUE_ORDERED_DRAIN;
> + if (sdkp->WCE) {
> + flush |= REQ_FLUSH;
> + if (sdkp->DPOFUA)
> + flush |= REQ_FUA;
> + }
>
> - blk_queue_ordered(sdkp->disk->queue, ordered);
> + blk_queue_flush(sdkp->disk->queue, flush);
>
> set_capacity(disk, sdkp->capacity);
> kfree(buffer);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 96ef5f1..6003f7c 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -355,8 +355,10 @@ struct request_queue
> struct blk_trace *blk_trace;
> #endif
> /*
> - * reserved for flush operations
> + * for flush operations
> */
> + unsigned int flush_flags;
> +
> unsigned int ordered, next_ordered, ordseq;
> int orderr, ordcolor;
> struct request pre_flush_rq, bar_rq, post_flush_rq;
> @@ -863,8 +865,8 @@ extern void blk_queue_update_dma_alignment(struct request_queue *, int);
> extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
> 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 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
> -extern int blk_queue_ordered(struct request_queue *, unsigned);
> extern bool blk_do_ordered(struct request_queue *, struct request **);
> extern unsigned blk_ordered_cur_seq(struct request_queue *);
> extern unsigned blk_ordered_req_seq(struct request *);
> --
> 1.7.1
>
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