On Wed, 2010-11-10 at 16:02 -0500, Christoph Hellwig wrote:
> Since 2.6.37-rc barriers have been replaced with the REQ_FLUSH and
> REQ_FUA flags. Both flags work on all devices without a need to check
> for barrier functionality.
>
> Use this fact to simplify the iblock code. Use the REQ_FUA flag when
> we report a write cache or if the target set the FUA bit, and remove
> all the barrier detection code.
>
> Btw, I think iblock would benefit from sharing a common option with
> the file backend for enabling or disabling the option to provide
> a voltile write cache to the initiator or not.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Everything looks good, thanks for the cleanup Christoph! Committed as
67f4b72.
Also just FYI, the modepage caching bit (WCE=1) and EVPD 0x86 volatile
cache supported bit (V_SUP=1) can be explictly disabled by backends
reporting support for write caching emulation
(se_subsystem_api->write_cache_emulated() == 1) with:
echo 0 > /sys/kernel/config/target/core/$HBA/$DEV/attrib/emulate_write_cache
Note the currently available backend overrides for various control bits
look like:
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_dpo
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_fua_read
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_fua_write
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_tas
-rw-r--r-- 1 root root 4096 2010-11-10 23:39 emulate_tpu
-rw-r--r-- 1 root root 4096 2010-11-10 23:39 emulate_tpws
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_ua_intlck_ctrl
-rw-r--r-- 1 root root 4096 2010-11-09 01:18 emulate_write_cache
>
> Index: lio-core-2.6/drivers/target/target_core_iblock.c
> ===================================================================
> --- lio-core-2.6.orig/drivers/target/target_core_iblock.c 2010-11-09 11:23:20.921529680 +0100
> +++ lio-core-2.6/drivers/target/target_core_iblock.c 2010-11-09 12:16:20.918196346 +0100
> @@ -130,8 +130,6 @@ static void *iblock_allocate_virtdevice(
> return ib_dev;
> }
>
> -static int __iblock_do_sync_cache(struct se_device *);
> -
> static struct se_device *iblock_create_virtdevice(
> struct se_hba *hba,
> struct se_subsystem_dev *se_dev,
> @@ -194,14 +192,7 @@ static struct se_device *iblock_create_v
> goto failed;
>
> ib_dev->ibd_depth = dev->queue_depth;
> - /*
> - * Check if the underlying struct block_device supports the
> - * block/blk-barrier.c:blkdev_issue_flush() call, depending upon
> - * which the SCSI mode page bits for WriteCache=1 and DPOFUA=1
> - * will be enabled by TCM Core.
> - */
> - if (__iblock_do_sync_cache(dev) == 0)
> - ib_dev->ibd_flags |= IBDF_BDEV_ISSUE_FLUSH;
> +
> /*
> * Check if the underlying struct block_device request_queue supports
> * the QUEUE_FLAG_DISCARD bit for UNMAP/WRITE_SAME in SCSI + TRIM
> @@ -352,51 +343,37 @@ static unsigned long long iblock_emulate
> return blocks_long;
> }
>
> -static int __iblock_do_sync_cache(struct se_device *dev)
> -{
> - struct iblock_dev *ib_dev = (struct iblock_dev *)dev->dev_ptr;
> - sector_t error_sector;
> - int ret;
> -
> - ret = blkdev_issue_flush(ib_dev->ibd_bd, GFP_KERNEL, &error_sector);
> - if (ret != 0) {
> - printk(KERN_ERR "IBLOCK: block_issue_flush() failed: %d "
> - " error_sector: %llu\n", ret,
> - (unsigned long long)error_sector);
> - return -1;
> - }
> - DEBUG_IBLOCK("IBLOCK: Called block_issue_flush()\n");
> - return 0;
> -}
> -
> /*
> - * Called by target_core_transport():transport_emulate_control_cdb()
> - * to emulate SYCHRONIZE_CACHE_*
> + * Emulate SYCHRONIZE_CACHE_*
> */
> -void iblock_emulate_sync_cache(struct se_task *task)
> +static void iblock_emulate_sync_cache(struct se_task *task)
> {
> struct se_cmd *cmd = TASK_CMD(task);
> - int ret, immed = (T_TASK(cmd)->t_task_cdb[1] & 0x2);
> + struct iblock_dev *ib_dev = cmd->se_dev->dev_ptr;
> + int immed = (T_TASK(cmd)->t_task_cdb[1] & 0x2);
> + sector_t error_sector;
> + int ret;
> +
> /*
> * If the Immediate bit is set, queue up the GOOD response
> * for this SYNCHRONIZE_CACHE op
> */
> if (immed)
> transport_complete_sync_cache(cmd, 1);
> +
> /*
> - * block/blk-barrier.c:block_issue_flush() does not support a
> - * LBA + Range synchronization method, so for this case we
> - * have to flush the entire cache.
> + * blkdev_issue_flush() does not support a specifying a range, so
> + * we have to flush the entire cache.
> */
> - ret = __iblock_do_sync_cache(cmd->se_dev);
> - if (ret < 0) {
> - if (!(immed))
> - transport_complete_sync_cache(cmd, 0);
> - return;
> + ret = blkdev_issue_flush(ib_dev->ibd_bd, GFP_KERNEL, &error_sector);
> + if (ret != 0) {
> + printk(KERN_ERR "IBLOCK: block_issue_flush() failed: %d "
> + " error_sector: %llu\n", ret,
> + (unsigned long long)error_sector);
> }
>
> - if (!(immed))
> - transport_complete_sync_cache(cmd, 1);
> + if (!immed)
> + transport_complete_sync_cache(cmd, ret == 0);
> }
>
> /*
> @@ -405,11 +382,7 @@ void iblock_emulate_sync_cache(struct se
> */
> int iblock_emulated_write_cache(struct se_device *dev)
> {
> - struct iblock_dev *ib_dev = (struct iblock_dev *)dev->dev_ptr;
> - /*
> - * Only return WCE if ISSUE_FLUSH is supported
> - */
> - return (ib_dev->ibd_flags & IBDF_BDEV_ISSUE_FLUSH) ? 1 : 0;
> + return 1;
> }
>
> int iblock_emulated_dpo(struct se_device *dev)
> @@ -423,11 +396,7 @@ int iblock_emulated_dpo(struct se_device
> */
> int iblock_emulated_fua_write(struct se_device *dev)
> {
> - struct iblock_dev *ib_dev = (struct iblock_dev *)dev->dev_ptr;
> - /*
> - * Only return FUA WRITE if ISSUE_FLUSH is supported
> - */
> - return (ib_dev->ibd_flags & IBDF_BDEV_ISSUE_FLUSH) ? 1 : 0;
> + return 1;
> }
>
> int iblock_emulated_fua_read(struct se_device *dev)
> @@ -442,8 +411,22 @@ static int iblock_do_task(struct se_task
> struct iblock_dev *ibd = (struct iblock_dev *)req->ib_dev;
> struct request_queue *q = bdev_get_queue(ibd->ibd_bd);
> struct bio *bio = req->ib_bio, *nbio = NULL;
> - int write = (TASK_CMD(task)->data_direction == DMA_TO_DEVICE);
> - int ret;
> + int rw;
> +
> + if (TASK_CMD(task)->data_direction == DMA_TO_DEVICE) {
> + /*
> + * Force data to disk if we pretend to not have a volatile
> + * write cache, or the initiator set the Force Unit Access bit.
> + */
> + if (DEV_ATTRIB(dev)->emulate_write_cache == 0 ||
> + (DEV_ATTRIB(dev)->emulate_fua_write > 0 &&
> + T_TASK(task->task_se_cmd)->t_tasks_fua))
> + rw = WRITE_FUA;
> + else
> + rw = WRITE;
> + } else {
> + rw = READ;
> + }
>
> while (bio) {
> nbio = bio->bi_next;
> @@ -451,30 +434,12 @@ static int iblock_do_task(struct se_task
> DEBUG_IBLOCK("Calling submit_bio() task: %p bio: %p"
> " bio->bi_sector: %llu\n", task, bio, bio->bi_sector);
>
> - submit_bio(write, bio);
> + submit_bio(rw, bio);
> bio = nbio;
> }
>
> if (q->unplug_fn)
> q->unplug_fn(q);
> - /*
> - * Check for Forced Unit Access WRITE emulation
> - */
> - if ((DEV_ATTRIB(dev)->emulate_write_cache > 0) &&
> - (DEV_ATTRIB(dev)->emulate_fua_write > 0) &&
> - write && T_TASK(task->task_se_cmd)->t_tasks_fua) {
> - /*
> - * We might need to be a bit smarter here
> - * and return some sense data to let the initiator
> - * know the FUA WRITE cache sync failed..?
> - */
> - ret = __iblock_do_sync_cache(dev);
> - if (ret < 0) {
> - printk(KERN_ERR "__iblock_do_sync_cache()"
> - " failed for FUA Write\n");
> - }
> - }
> -
> return PYX_TRANSPORT_SENT_TO_TRANSPORT;
> }
>
> Index: lio-core-2.6/drivers/target/target_core_iblock.h
> ===================================================================
> --- lio-core-2.6.orig/drivers/target/target_core_iblock.h 2010-11-09 11:23:25.454863013 +0100
> +++ lio-core-2.6/drivers/target/target_core_iblock.h 2010-11-09 11:23:35.334863016 +0100
> @@ -23,7 +23,6 @@ struct iblock_req {
>
> #define IBDF_HAS_UDEV_PATH 0x01
> #define IBDF_HAS_FORCE 0x02
> -#define IBDF_BDEV_ISSUE_FLUSH 0x04
>
> struct iblock_dev {
> unsigned char ibd_udev_path[SE_UDEV_PATH_LEN];
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