Make BLOCKIO honor SYNCHRONIZE_CACHE commands

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@1738 d57e44dd-8a1f-0410-8b47-8ef2f437770f

iscsi-scst/README

@@ -404,6 +404,7 @@ both iSCSI-SCST targets will look like:
 |   |   |   `-- export0 -> ../../../targets/iscsi/iqn.2006-10.net.vlnb:tgt1/ini_groups/special_ini/luns/0
 |   |   |-- filename
 |   |   |-- handler -> ../../handlers/vdisk_blockio
+|   |   |-- nv_cache
 |   |   |-- read_only
 |   |   |-- removable
 |   |   |-- resync_size

iscsi-scst/README_in-tree

@@ -301,6 +301,7 @@ both iSCSI-SCST targets will look like:
 |   |   |   `-- export0 -> ../../../targets/iscsi/iqn.2006-10.net.vlnb:tgt1/ini_groups/special_ini/luns/0
 |   |   |-- filename
 |   |   |-- handler -> ../../handlers/vdisk_blockio
+|   |   |-- nv_cache
 |   |   |-- read_only
 |   |   |-- removable
 |   |   |-- resync_size

qla2x00t/qla2x00-target/README

@@ -292,6 +292,7 @@ The resulting overall SCST sysfs hierarchy with initiator
 |   |   |   `-- export0 -> ../../../targets/qla2x00t/25:00:00:f0:98:87:92:f3/luns/0
 |   |   |-- filename
 |   |   |-- handler -> ../../handlers/vdisk_blockio
+|   |   |-- nv_cache
 |   |   |-- read_only
 |   |   |-- removable
 |   |   |-- resync_size

scst/README

@@ -1131,8 +1131,8 @@ between application and disk or need the large block throughput. See
 below for more info.
 
 The following parameters possible for vdisk_blockio: filename,
-blocksize, read_only, removable. See vdisk_fileio above for description
-of those parameters.
+blocksize, nv_cache, read_only, removable. See vdisk_fileio above for
+description of those parameters.
 
 Handler vdisk_nullio provides NULLIO mode to create virtual devices. In
 this mode no real I/O is done, but success returned to initiators.
@@ -1213,7 +1213,7 @@ For example:
 `-- write_through
 
 Each vdisk_blockio's device has the following attributes in
-/sys/kernel/scst_tgt/devices/device_name: blocksize, filename,
+/sys/kernel/scst_tgt/devices/device_name: blocksize, filename, nv_cache,
 read_only, removable, resync_size, size_mb, t10_dev_id, threads_num,
 threads_pool_type, type, usn. See above description of those parameters.
 
@@ -1421,6 +1421,19 @@ IMPORTANT: Since data in BLOCKIO and FILEIO modes are not consistent between
 	   simultaneously, you will almost instantly corrupt your data
 	   on that device.
 
+IMPORTANT: If SCST 1.x BLOCKIO worked by default in NV_CACHE mode, when
+=========  each device reported to remote initiators as having write through
+           caching. But if your backend block device has internal write
+	   back caching it might create a possibility for data loss of
+	   the cached in the internal cache data in case of a power
+	   failure. Starting from SCST 2.0 BLOCKIO works by default in
+	   non-NV_CACHE mode, when each device reported to remote
+	   initiators as having write back caching, and synchronizes the
+	   internal device's cache on each SYNCHRONIZE_CACHE command
+	   from the initiators. It might lead to some PERFORMANCE LOSS,
+	   so if you are are sure in your power supply and want to
+	   restore 1.x behavior, your should recreate your BLOCKIO
+	   devices in NV_CACHE mode.
 
 Pass-through mode
 -----------------

scst/README_in-tree

@@ -714,8 +714,8 @@ between application and disk or need the large block throughput. See
 below for more info.
 
 The following parameters possible for vdisk_blockio: filename,
-blocksize, read_only, removable. See vdisk_fileio above for description
-of those parameters.
+blocksize, nv_cache, read_only, removable. See vdisk_fileio above for
+description of those parameters.
 
 Handler vdisk_nullio provides NULLIO mode to create virtual devices. In
 this mode no real I/O is done, but success returned to initiators.
@@ -796,7 +796,7 @@ For example:
 `-- write_through
 
 Each vdisk_blockio's device has the following attributes in
-/sys/kernel/scst_tgt/devices/device_name: blocksize, filename,
+/sys/kernel/scst_tgt/devices/device_name: blocksize, filename, nv_cache,
 read_only, removable, resync_size, size_mb, t10_dev_id, threads_num,
 threads_pool_type, type, usn. See above description of those parameters.
 
@@ -1004,6 +1004,19 @@ IMPORTANT: Since data in BLOCKIO and FILEIO modes are not consistent between
 	   simultaneously, you will almost instantly corrupt your data
 	   on that device.
 
+IMPORTANT: If SCST 1.x BLOCKIO worked by default in NV_CACHE mode, when
+=========  each device reported to remote initiators as having write through
+           caching. But if your backend block device has internal write
+	   back caching it might create a possibility for data loss of
+	   the cached in the internal cache data in case of a power
+	   failure. Starting from SCST 2.0 BLOCKIO works by default in
+	   non-NV_CACHE mode, when each device reported to remote
+	   initiators as having write back caching, and synchronizes the
+	   internal device's cache on each SYNCHRONIZE_CACHE command
+	   from the initiators. It might lead to some PERFORMANCE LOSS,
+	   so if you are are sure in your power supply and want to
+	   restore 1.x behavior, your should recreate your BLOCKIO
+	   devices in NV_CACHE mode.
 
 Pass-through mode
 -----------------

scst/src/dev_handlers/scst_vdisk.c

@@ -41,6 +41,7 @@
 #include <asm/div64.h>
 #include <asm/unaligned.h>
 #include <linux/slab.h>
+#include <linux/bio.h>
 
 #define LOG_PREFIX			"dev_vdisk"
 
@@ -259,6 +260,7 @@ static void vdisk_exec_write(struct scst_cmd *cmd,
 	struct scst_vdisk_thr *thr, loff_t loff);
 static void blockio_exec_rw(struct scst_cmd *cmd, struct scst_vdisk_thr *thr,
 	u64 lba_start, int write);
+static int blockio_flush(struct block_device *bdev);
 static void vdisk_exec_verify(struct scst_cmd *cmd,
 	struct scst_vdisk_thr *thr, loff_t loff);
 static void vdisk_exec_read_capacity(struct scst_cmd *cmd);
@@ -372,6 +374,7 @@ static const struct attribute *vdisk_blockio_attrs[] = {
 	&vdev_size_attr.attr,
 	&vdisk_blocksize_attr.attr,
 	&vdisk_rd_only_attr.attr,
+	&vdisk_nv_cache_attr.attr,
 	&vdisk_removable_attr.attr,
 	&vdisk_filename_attr.attr,
 	&vdisk_resync_size_attr.attr,
@@ -602,6 +605,44 @@ static struct file *vdev_open_fd(const struct scst_vdisk_dev *virt_dev)
 	return fd;
 }
 
+static void vdisk_blockio_check_flush_support(struct scst_vdisk_dev *virt_dev)
+{
+	struct inode *inode;
+	struct file *fd;
+
+	TRACE_ENTRY();
+
+	if (!virt_dev->blockio || virt_dev->rd_only || virt_dev->nv_cache)
+		goto out;
+
+	fd = filp_open(virt_dev->filename, O_LARGEFILE, 0600);
+	if (IS_ERR(fd)) {
+		PRINT_ERROR("filp_open(%s) returned error %ld",
+			virt_dev->filename, PTR_ERR(fd));
+		goto out;
+	}
+
+	inode = fd->f_dentry->d_inode;
+
+	if (!S_ISBLK(inode->i_mode)) {
+		PRINT_ERROR("%s is NOT a block device", virt_dev->filename);
+		goto out_close;
+	}
+
+	if (blockio_flush(inode->i_bdev) != 0) {
+		PRINT_WARNING("Device %s doesn't support barriers, switching "
+			"to NV_CACHE mode", virt_dev->filename);
+		virt_dev->nv_cache = 1;
+	}
+
+out_close:
+	filp_close(fd, NULL);
+
+out:
+	TRACE_EXIT();
+	return;
+}
+
 /* Returns 0 on success and file size in *file_size, error code otherwise */
 static int vdisk_get_file_size(const char *filename, bool blockio,
 	loff_t *file_size)
@@ -695,7 +736,10 @@ static int vdisk_attach(struct scst_device *dev)
 				goto out;
 		}
 		virt_dev->file_size = err;
+
 		TRACE_DBG("size of file: %lld", (long long unsigned int)err);
+
+		vdisk_blockio_check_flush_support(virt_dev);
 	} else
 		virt_dev->file_size = 0;
 
@@ -1612,8 +1656,11 @@ static void vdisk_exec_mode_sense(struct scst_cmd *cmd)
 	pcode = cmd->cdb[2] & 0x3f;
 	subpcode = cmd->cdb[3];
 	msense_6 = (MODE_SENSE == cmd->cdb[0]);
-	dev_spec = ((virt_dev->dev->rd_only ||
-		     cmd->tgt_dev->acg_dev->rd_only) ? WP : 0) | DPOFUA;
+	dev_spec = (virt_dev->dev->rd_only ||
+		     cmd->tgt_dev->acg_dev->rd_only) ? WP : 0;
+
+	if (!virt_dev->blockio)
+		dev_spec |= DPOFUA;
 
 	length = scst_get_buf_first(cmd, &address);
 	if (unlikely(length <= 0)) {
@@ -2152,15 +2199,22 @@ static int vdisk_fsync(struct scst_vdisk_thr *thr, loff_t loff,
 	int res = 0;
 	struct scst_vdisk_dev *virt_dev =
 		(struct scst_vdisk_dev *)dev->dh_priv;
-	struct file *file = thr->fd;
+	struct file *file;
 
 	TRACE_ENTRY();
 
 	/* Hopefully, the compiler will generate the single comparison */
-	if (virt_dev->nv_cache || virt_dev->blockio || virt_dev->wt_flag ||
+	if (virt_dev->nv_cache || virt_dev->wt_flag ||
 	    virt_dev->o_direct_flag || virt_dev->nullio)
 		goto out;
 
+	if (virt_dev->blockio) {
+		res = blockio_flush(thr->bdev);
+		goto out;
+	}
+
+	file = thr->fd;
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 32)
 	res = sync_page_range(file->f_dentry->d_inode, file->f_mapping,
 		loff, len);
@@ -2179,8 +2233,6 @@ static int vdisk_fsync(struct scst_vdisk_thr *thr, loff_t loff,
 		}
 	}
 
-	/* ToDo: flush the device cache, if needed */
-
 out:
 	TRACE_EXIT_RES(res);
 	return res;
@@ -2500,7 +2552,7 @@ static void blockio_endio(struct bio *bio, int error)
 		return 1;
 #endif
 
-	if (unlikely(!test_bit(BIO_UPTODATE, &bio->bi_flags))) {
+	if (unlikely(!bio_flagged(bio, BIO_UPTODATE))) {
 		if (error == 0) {
 			PRINT_ERROR("Not up to date bio with error 0 for "
 				"cmd %p, returning -EIO", blockio_work->cmd);
@@ -2606,6 +2658,17 @@ static void blockio_exec_rw(struct scst_cmd *cmd, struct scst_vdisk_thr *thr,
 					(virt_dev->block_shift - 9);
 				bio->bi_bdev = bdev;
 				bio->bi_private = blockio_work;
+				/*
+				 * Better to fail fast w/o any local recovery
+				 * and retries.
+				 */
+#ifdef BIO_RW_FAILFAST
+				bio->bi_rw |= (1 << BIO_RW_FAILFAST);
+#else
+				bio->bi_rw |= (1 << BIO_RW_FAILFAST_DEV) |
+					      (1 << BIO_RW_FAILFAST_TRANSPORT) |
+					      (1 << BIO_RW_FAILFAST_DRIVER);
+#endif
 #if 0 /* It could be win, but could be not, so a performance study is needed */
 				bio->bi_rw |= 1 << BIO_RW_SYNC;
 #endif
@@ -2670,6 +2733,20 @@ out_no_mem:
 	goto out;
 }
 
+static int blockio_flush(struct block_device *bdev)
+{
+	int res = 0;
+
+	TRACE_ENTRY();
+
+	res = blkdev_issue_flush(bdev, NULL);
+	if (res != 0)
+		PRINT_ERROR("blkdev_issue_flush() failed: %d", res);
+
+	TRACE_EXIT_RES(res);
+	return res;
+}
+
 static void vdisk_exec_verify(struct scst_cmd *cmd,
 	struct scst_vdisk_thr *thr, loff_t loff)
 {
@@ -3196,7 +3273,7 @@ static int vdev_blockio_add_device(const char *device_name, char *params)
 {
 	int res = 0;
 	const char *allowed_params[] = { "filename", "read_only", "removable",
-					 "blocksize", NULL };
+					 "blocksize", "nv_cache", NULL };
 	struct scst_vdisk_dev *virt_dev;
 
 	TRACE_ENTRY();