exofs: Multi-device mirror support

This patch changes on-disk format, it is accompanied with a parallel
patch to mkfs.exofs that enables multi-device capabilities.

After this patch, old exofs will refuse to mount a new formatted FS and
new exofs will refuse an old format. This is done by moving the magic
field offset inside the FSCB. A new FSCB *version* field was added. In
the future, exofs will refuse to mount unmatched FSCB version. To
up-grade or down-grade an exofs one must use mkfs.exofs --upgrade option
before mounting.

Introduced, a new object that contains a *device-table*. This object
contains the default *data-map* and a linear array of devices
information, which identifies the devices used in the filesystem. This
object is only written to offline by mkfs.exofs. This is why it is kept
separate from the FSCB, since the later is written to while mounted.

Same partition number, same object number is used on all devices only
the device varies.

* define the new format, then load the device table on mount time make
  sure every thing is supported.

* Change I/O engine to now support Mirror IO, .i.e write same data
  to multiple devices, read from a random device to spread the
  read-load from multiple clients (TODO: stripe read)

Implementation notes:
 A few points introduced in previous patch should be mentioned here:

* Special care was made so absolutlly all operation that have any chance
  of failing are done before any osd-request is executed. This is to
  minimize the need for a data consistency recovery, to only real IO
  errors.

* Each IO state has a kref. It starts at 1, any osd-request executed
  will increment the kref, finally when all are executed the first ref
  is dropped. At IO-done, each request completion decrements the kref,
  the last one to return executes the internal _last_io() routine.
  _last_io() will call the registered io_state_done. On sync mode a
  caller does not supply a done method, indicating a synchronous
  request, the caller is put to sleep and a special io_state_done is
  registered that will awaken the caller. Though also in sync mode all
  operations are executed in parallel.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 212 insertions, 8 deletions

diff --git a/fs/exofs/super.c b/fs/exofs/super.c
index 4cd97f5..a1d1e77 100644
--- a/fs/exofs/super.c
+++ b/fs/exofs/super.c
@@ -214,12 +214,17 @@ int exofs_sync_fs(struct super_block *sb, int wait)
 	if (ret)
 		goto out;
 
-	ios->length = sizeof(*fscb);
+	/* Note: We only write the changing part of the fscb. .i.e upto the
+	 *       the fscb->s_dev_table_oid member. There is no read-modify-write
+	 *       here.
+	 */
+	ios->length = offsetof(struct exofs_fscb, s_dev_table_oid);
 	memset(fscb, 0, ios->length);
 	fscb->s_nextid = cpu_to_le64(sbi->s_nextid);
 	fscb->s_numfiles = cpu_to_le32(sbi->s_numfiles);
 	fscb->s_magic = cpu_to_le16(sb->s_magic);
 	fscb->s_newfs = 0;
+	fscb->s_version = EXOFS_FSCB_VER;
 
 	ios->obj.id = EXOFS_SUPER_ID;
 	ios->offset = 0;
@@ -257,6 +262,20 @@ static void _exofs_print_device(const char *msg, const char *dev_path,
 		msg, dev_path ?: "", odi->osdname, _LLU(pid));
 }
 
+void exofs_free_sbi(struct exofs_sb_info *sbi)
+{
+	while (sbi->s_numdevs) {
+		int i = --sbi->s_numdevs;
+		struct osd_dev *od = sbi->s_ods[i];
+
+		if (od) {
+			sbi->s_ods[i] = NULL;
+			osduld_put_device(od);
+		}
+	}
+	kfree(sbi);
+}
+
 /*
  * This function is called when the vfs is freeing the superblock.  We just
  * need to free our own part.
@@ -279,12 +298,182 @@ static void exofs_put_super(struct super_block *sb)
 				  msecs_to_jiffies(100));
 	}
 
-	_exofs_print_device("Unmounting", NULL, sbi->s_dev, sbi->s_pid);
-	osduld_put_device(sbi->s_dev);
-	kfree(sb->s_fs_info);
+	_exofs_print_device("Unmounting", NULL, sbi->s_ods[0], sbi->s_pid);
+
+	exofs_free_sbi(sbi);
 	sb->s_fs_info = NULL;
 }
 
+static int _read_and_match_data_map(struct exofs_sb_info *sbi, unsigned numdevs,
+				    struct exofs_device_table *dt)
+{
+	sbi->data_map.odm_num_comps   =
+				le32_to_cpu(dt->dt_data_map.cb_num_comps);
+	sbi->data_map.odm_stripe_unit =
+				le64_to_cpu(dt->dt_data_map.cb_stripe_unit);
+	sbi->data_map.odm_group_width =
+				le32_to_cpu(dt->dt_data_map.cb_group_width);
+	sbi->data_map.odm_group_depth =
+				le32_to_cpu(dt->dt_data_map.cb_group_depth);
+	sbi->data_map.odm_mirror_cnt  =
+				le32_to_cpu(dt->dt_data_map.cb_mirror_cnt);
+	sbi->data_map.odm_raid_algorithm  =
+				le32_to_cpu(dt->dt_data_map.cb_raid_algorithm);
+
+/* FIXME: Hard coded mirror only for now. if not so do not mount */
+	if ((sbi->data_map.odm_num_comps != numdevs) ||
+	    (sbi->data_map.odm_stripe_unit != EXOFS_BLKSIZE) ||
+	    (sbi->data_map.odm_raid_algorithm != PNFS_OSD_RAID_0) ||
+	    (sbi->data_map.odm_mirror_cnt != (numdevs - 1)))
+		return -EINVAL;
+	else
+		return 0;
+}
+
+/* @odi is valid only as long as @fscb_dev is valid */
+static int exofs_devs_2_odi(struct exofs_dt_device_info *dt_dev,
+			     struct osd_dev_info *odi)
+{
+	odi->systemid_len = le32_to_cpu(dt_dev->systemid_len);
+	memcpy(odi->systemid, dt_dev->systemid, odi->systemid_len);
+
+	odi->osdname_len = le32_to_cpu(dt_dev->osdname_len);
+	odi->osdname = dt_dev->osdname;
+
+	/* FIXME support long names. Will need a _put function */
+	if (dt_dev->long_name_offset)
+		return -EINVAL;
+
+	/* Make sure osdname is printable!
+	 * mkexofs should give us space for a null-terminator else the
+	 * device-table is invalid.
+	 */
+	if (unlikely(odi->osdname_len >= sizeof(dt_dev->osdname)))
+		odi->osdname_len = sizeof(dt_dev->osdname) - 1;
+	dt_dev->osdname[odi->osdname_len] = 0;
+
+	/* If it's all zeros something is bad we read past end-of-obj */
+	return !(odi->systemid_len || odi->osdname_len);
+}
+
+static int exofs_read_lookup_dev_table(struct exofs_sb_info **psbi,
+				       unsigned table_count)
+{
+	struct exofs_sb_info *sbi = *psbi;
+	struct osd_dev *fscb_od;
+	struct osd_obj_id obj = {.partition = sbi->s_pid,
+				 .id = EXOFS_DEVTABLE_ID};
+	struct exofs_device_table *dt;
+	unsigned table_bytes = table_count * sizeof(dt->dt_dev_table[0]) +
+					     sizeof(*dt);
+	unsigned numdevs, i;
+	int ret;
+
+	dt = kmalloc(table_bytes, GFP_KERNEL);
+	if (unlikely(!dt)) {
+		EXOFS_ERR("ERROR: allocating %x bytes for device table\n",
+			  table_bytes);
+		return -ENOMEM;
+	}
+
+	fscb_od = sbi->s_ods[0];
+	sbi->s_ods[0] = NULL;
+	sbi->s_numdevs = 0;
+	ret = exofs_read_kern(fscb_od, sbi->s_cred, &obj, 0, dt, table_bytes);
+	if (unlikely(ret)) {
+		EXOFS_ERR("ERROR: reading device table\n");
+		goto out;
+	}
+
+	numdevs = le64_to_cpu(dt->dt_num_devices);
+	if (unlikely(!numdevs)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	WARN_ON(table_count != numdevs);
+
+	ret = _read_and_match_data_map(sbi, numdevs, dt);
+	if (unlikely(ret))
+		goto out;
+
+	if (likely(numdevs > 1)) {
+		unsigned size = numdevs * sizeof(sbi->s_ods[0]);
+
+		sbi = krealloc(sbi, sizeof(*sbi) + size, GFP_KERNEL);
+		if (unlikely(!sbi)) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		memset(&sbi->s_ods[1], 0, size - sizeof(sbi->s_ods[0]));
+		*psbi = sbi;
+	}
+
+	for (i = 0; i < numdevs; i++) {
+		struct exofs_fscb fscb;
+		struct osd_dev_info odi;
+		struct osd_dev *od;
+
+		if (exofs_devs_2_odi(&dt->dt_dev_table[i], &odi)) {
+			EXOFS_ERR("ERROR: Read all-zeros device entry\n");
+			ret = -EINVAL;
+			goto out;
+		}
+
+		printk(KERN_NOTICE "Add device[%d]: osd_name-%s\n",
+		       i, odi.osdname);
+
+		/* On all devices the device table is identical. The user can
+		 * specify any one of the participating devices on the command
+		 * line. We always keep them in device-table order.
+		 */
+		if (fscb_od && osduld_device_same(fscb_od, &odi)) {
+			sbi->s_ods[i] = fscb_od;
+			++sbi->s_numdevs;
+			fscb_od = NULL;
+			continue;
+		}
+
+		od = osduld_info_lookup(&odi);
+		if (unlikely(IS_ERR(od))) {
+			ret = PTR_ERR(od);
+			EXOFS_ERR("ERROR: device requested is not found "
+				  "osd_name-%s =>%d\n", odi.osdname, ret);
+			goto out;
+		}
+
+		sbi->s_ods[i] = od;
+		++sbi->s_numdevs;
+
+		/* Read the fscb of the other devices to make sure the FS
+		 * partition is there.
+		 */
+		ret = exofs_read_kern(od, sbi->s_cred, &obj, 0, &fscb,
+				      sizeof(fscb));
+		if (unlikely(ret)) {
+			EXOFS_ERR("ERROR: Malformed participating device "
+				  "error reading fscb osd_name-%s\n",
+				  odi.osdname);
+			goto out;
+		}
+
+		/* TODO: verify other information is correct and FS-uuid
+		 *	 matches. Benny what did you say about device table
+		 *	 generation and old devices?
+		 */
+	}
+
+out:
+	kfree(dt);
+	if (unlikely(!ret && fscb_od)) {
+		EXOFS_ERR(
+		      "ERROR: Bad device-table container device not present\n");
+		osduld_put_device(fscb_od);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
 /*
  * Read the superblock from the OSD and fill in the fields
  */
@@ -296,6 +485,7 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
 	struct osd_dev *od;		/* Master device                 */
 	struct exofs_fscb fscb;		/*on-disk superblock info        */
 	struct osd_obj_id obj;
+	unsigned table_count;
 	int ret;
 
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
@@ -309,7 +499,8 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
 		goto free_sbi;
 	}
 
-	sbi->s_dev = od;
+	sbi->s_ods[0] = od;
+	sbi->s_numdevs = 1;
 	sbi->s_pid = opts->pid;
 	sbi->s_timeout = opts->timeout;
 
@@ -342,11 +533,24 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
 		ret = -EINVAL;
 		goto free_sbi;
 	}
+	if (le32_to_cpu(fscb.s_version) != EXOFS_FSCB_VER) {
+		EXOFS_ERR("ERROR: Bad FSCB version expected-%d got-%d\n",
+			  EXOFS_FSCB_VER, le32_to_cpu(fscb.s_version));
+		ret = -EINVAL;
+		goto free_sbi;
+	}
 
 	/* start generation numbers from a random point */
 	get_random_bytes(&sbi->s_next_generation, sizeof(u32));
 	spin_lock_init(&sbi->s_next_gen_lock);
 
+	table_count = le64_to_cpu(fscb.s_dev_table_count);
+	if (table_count) {
+		ret = exofs_read_lookup_dev_table(&sbi, table_count);
+		if (unlikely(ret))
+			goto free_sbi;
+	}
+
 	/* set up operation vectors */
 	sb->s_fs_info = sbi;
 	sb->s_op = &exofs_sops;
@@ -374,14 +578,14 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
 		goto free_sbi;
 	}
 
-	_exofs_print_device("Mounting", opts->dev_name, sbi->s_dev, sbi->s_pid);
+	_exofs_print_device("Mounting", opts->dev_name, sbi->s_ods[0],
+			    sbi->s_pid);
 	return 0;
 
 free_sbi:
 	EXOFS_ERR("Unable to mount exofs on %s pid=0x%llx err=%d\n",
 		  opts->dev_name, sbi->s_pid, ret);
-	osduld_put_device(sbi->s_dev); /* NULL safe */
-	kfree(sbi);
+	exofs_free_sbi(sbi);
 	return ret;
 }