Re: [PATCH v9 04/41] btrfs: Get zone information of zoned block devices

[Naohiro Aota <naohiro.aota@wdc.com>]

On Mon, Nov 02, 2020 at 11:53:35AM -0500, Josef Bacik wrote:
>On 10/30/20 9:51 AM, Naohiro Aota wrote:
>>If a zoned block device is found, get its zone information (number of zones
>>and zone size) using the new helper function btrfs_get_dev_zone_info().  To
>>avoid costly run-time zone report commands to test the device zones type
>>during block allocation, attach the seq_zones bitmap to the device
>>structure to indicate if a zone is sequential or accept random writes. Also
>>it attaches the empty_zones bitmap to indicate if a zone is empty or not.
>>
>>This patch also introduces the helper function btrfs_dev_is_sequential() to
>>test if the zone storing a block is a sequential write required zone and
>>btrfs_dev_is_empty_zone() to test if the zone is a empty zone.
>>
>>Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>>Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
>>Reviewed-by: Josef Bacik <josef@toxicpanda.com>
>>---
>>  fs/btrfs/Makefile      |   1 +
>>  fs/btrfs/dev-replace.c |   5 ++
>>  fs/btrfs/super.c       |   5 ++
>>  fs/btrfs/volumes.c     |  19 ++++-
>>  fs/btrfs/volumes.h     |   4 +
>>  fs/btrfs/zoned.c       | 176 +++++++++++++++++++++++++++++++++++++++++
>>  fs/btrfs/zoned.h       |  86 ++++++++++++++++++++
>>  7 files changed, 294 insertions(+), 2 deletions(-)
>>  create mode 100644 fs/btrfs/zoned.c
>>  create mode 100644 fs/btrfs/zoned.h
>>
>>diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
>>index e738f6206ea5..0497fdc37f90 100644
>>--- a/fs/btrfs/Makefile
>>+++ b/fs/btrfs/Makefile
>>@@ -16,6 +16,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
>>  btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
>>  btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
>>  btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) += ref-verify.o
>>+btrfs-$(CONFIG_BLK_DEV_ZONED) += zoned.o
>>  btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \
>>  	tests/extent-buffer-tests.o tests/btrfs-tests.o \
>>diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
>>index 20ce1970015f..6f6d77224c2b 100644
>>--- a/fs/btrfs/dev-replace.c
>>+++ b/fs/btrfs/dev-replace.c
>>@@ -21,6 +21,7 @@
>>  #include "rcu-string.h"
>>  #include "dev-replace.h"
>>  #include "sysfs.h"
>>+#include "zoned.h"
>>  /*
>>   * Device replace overview
>>@@ -291,6 +292,10 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
>>  	set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
>>  	device->fs_devices = fs_info->fs_devices;
>>+	ret = btrfs_get_dev_zone_info(device);
>>+	if (ret)
>>+		goto error;
>>+
>>  	mutex_lock(&fs_info->fs_devices->device_list_mutex);
>>  	list_add(&device->dev_list, &fs_info->fs_devices->devices);
>>  	fs_info->fs_devices->num_devices++;
>>diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>>index 8840a4fa81eb..ed55014fd1bd 100644
>>--- a/fs/btrfs/super.c
>>+++ b/fs/btrfs/super.c
>>@@ -2462,6 +2462,11 @@ static void __init btrfs_print_mod_info(void)
>>  #endif
>>  #ifdef CONFIG_BTRFS_FS_REF_VERIFY
>>  			", ref-verify=on"
>>+#endif
>>+#ifdef CONFIG_BLK_DEV_ZONED
>>+			", zoned=yes"
>>+#else
>>+			", zoned=no"
>>  #endif
>>  			;
>>  	pr_info("Btrfs loaded, crc32c=%s%s\n", crc32c_impl(), options);
>>diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>index 58b9c419a2b6..e787bf89f761 100644
>>--- a/fs/btrfs/volumes.c
>>+++ b/fs/btrfs/volumes.c
>>@@ -31,6 +31,7 @@
>>  #include "space-info.h"
>>  #include "block-group.h"
>>  #include "discard.h"
>>+#include "zoned.h"
>>  const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
>>  	[BTRFS_RAID_RAID10] = {
>>@@ -374,6 +375,7 @@ void btrfs_free_device(struct btrfs_device *device)
>>  	rcu_string_free(device->name);
>>  	extent_io_tree_release(&device->alloc_state);
>>  	bio_put(device->flush_bio);
>>+	btrfs_destroy_dev_zone_info(device);
>>  	kfree(device);
>>  }
>>@@ -667,6 +669,11 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
>>  	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
>>  	device->mode = flags;
>>+	/* Get zone type information of zoned block devices */
>>+	ret = btrfs_get_dev_zone_info(device);
>>+	if (ret != 0)
>>+		goto error_free_page;
>>+
>>  	fs_devices->open_devices++;
>>  	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
>>  	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
>>@@ -1143,6 +1150,7 @@ static void btrfs_close_one_device(struct btrfs_device *device)
>>  		device->bdev = NULL;
>>  	}
>>  	clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
>>+	btrfs_destroy_dev_zone_info(device);
>>  	device->fs_info = NULL;
>>  	atomic_set(&device->dev_stats_ccnt, 0);
>>@@ -2543,6 +2551,14 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>  	}
>>  	rcu_assign_pointer(device->name, name);
>>+	device->fs_info = fs_info;
>>+	device->bdev = bdev;
>>+
>>+	/* Get zone type information of zoned block devices */
>>+	ret = btrfs_get_dev_zone_info(device);
>>+	if (ret)
>>+		goto error_free_device;
>>+
>>  	trans = btrfs_start_transaction(root, 0);
>>  	if (IS_ERR(trans)) {
>>  		ret = PTR_ERR(trans);
>>@@ -2559,8 +2575,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>  					 fs_info->sectorsize);
>>  	device->disk_total_bytes = device->total_bytes;
>>  	device->commit_total_bytes = device->total_bytes;
>>-	device->fs_info = fs_info;
>>-	device->bdev = bdev;
>>  	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
>>  	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
>>  	device->mode = FMODE_EXCL;
>>@@ -2707,6 +2721,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>  		sb->s_flags |= SB_RDONLY;
>>  	if (trans)
>>  		btrfs_end_transaction(trans);
>>+	btrfs_destroy_dev_zone_info(device);
>>  error_free_device:
>>  	btrfs_free_device(device);
>>  error:
>>diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>>index bf27ac07d315..9c07b97a2260 100644
>>--- a/fs/btrfs/volumes.h
>>+++ b/fs/btrfs/volumes.h
>>@@ -51,6 +51,8 @@ struct btrfs_io_geometry {
>>  #define BTRFS_DEV_STATE_REPLACE_TGT	(3)
>>  #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
>>+struct btrfs_zoned_device_info;
>>+
>>  struct btrfs_device {
>>  	struct list_head dev_list; /* device_list_mutex */
>>  	struct list_head dev_alloc_list; /* chunk mutex */
>>@@ -64,6 +66,8 @@ struct btrfs_device {
>>  	struct block_device *bdev;
>>+	struct btrfs_zoned_device_info *zone_info;
>>+
>>  	/* the mode sent to blkdev_get */
>>  	fmode_t mode;
>>diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
>>new file mode 100644
>>index 000000000000..5657d654bc44
>>--- /dev/null
>>+++ b/fs/btrfs/zoned.c
>>@@ -0,0 +1,176 @@
>>+// SPDX-License-Identifier: GPL-2.0
>>+
>>+#include <linux/slab.h>
>>+#include <linux/blkdev.h>
>>+#include "ctree.h"
>>+#include "volumes.h"
>>+#include "zoned.h"
>>+#include "rcu-string.h"
>>+
>>+/* Maximum number of zones to report per blkdev_report_zones() call */
>>+#define BTRFS_REPORT_NR_ZONES   4096
>>+
>>+static int copy_zone_info_cb(struct blk_zone *zone, unsigned int idx,
>>+			     void *data)
>>+{
>>+	struct blk_zone *zones = data;
>>+
>>+	memcpy(&zones[idx], zone, sizeof(*zone));
>>+
>>+	return 0;
>>+}
>>+
>>+static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
>>+			       struct blk_zone *zones, unsigned int *nr_zones)
>>+{
>>+	int ret;
>>+
>>+	if (!*nr_zones)
>>+		return 0;
>>+
>>+	ret = blkdev_report_zones(device->bdev, pos >> SECTOR_SHIFT, *nr_zones,
>>+				  copy_zone_info_cb, zones);
>>+	if (ret < 0) {
>>+		btrfs_err_in_rcu(device->fs_info,
>>+				 "get zone at %llu on %s failed %d", pos,
>>+				 rcu_str_deref(device->name), ret);
>>+		return ret;
>>+	}
>>+	*nr_zones = ret;
>>+	if (!ret)
>>+		return -EIO;
>>+
>>+	return 0;
>>+}
>>+
>>+int btrfs_get_dev_zone_info(struct btrfs_device *device)
>>+{
>>+	struct btrfs_zoned_device_info *zone_info = NULL;
>>+	struct block_device *bdev = device->bdev;
>>+	sector_t nr_sectors = bdev->bd_part->nr_sects;
>>+	sector_t sector = 0;
>>+	struct blk_zone *zones = NULL;
>>+	unsigned int i, nreported = 0, nr_zones;
>>+	unsigned int zone_sectors;
>>+	int ret;
>>+	char devstr[sizeof(device->fs_info->sb->s_id) +
>>+		    sizeof(" (device )") - 1];
>>+
>>+	if (!bdev_is_zoned(bdev))
>>+		return 0;
>>+
>>+	if (device->zone_info)
>>+		return 0;
>>+
>>+	zone_info = kzalloc(sizeof(*zone_info), GFP_KERNEL);
>>+	if (!zone_info)
>>+		return -ENOMEM;
>>+
>>+	zone_sectors = bdev_zone_sectors(bdev);
>>+	ASSERT(is_power_of_2(zone_sectors));
>>+	zone_info->zone_size = (u64)zone_sectors << SECTOR_SHIFT;
>>+	zone_info->zone_size_shift = ilog2(zone_info->zone_size);
>>+	zone_info->nr_zones = nr_sectors >> ilog2(bdev_zone_sectors(bdev));
>>+	if (!IS_ALIGNED(nr_sectors, zone_sectors))
>>+		zone_info->nr_zones++;
>>+
>>+	zone_info->seq_zones = bitmap_zalloc(zone_info->nr_zones, GFP_KERNEL);
>>+	if (!zone_info->seq_zones) {
>>+		ret = -ENOMEM;
>>+		goto out;
>>+	}
>>+
>>+	zone_info->empty_zones = bitmap_zalloc(zone_info->nr_zones, GFP_KERNEL);
>>+	if (!zone_info->empty_zones) {
>>+		ret = -ENOMEM;
>>+		goto out;
>>+	}
>>+
>>+	zones = kcalloc(BTRFS_REPORT_NR_ZONES,
>>+			sizeof(struct blk_zone), GFP_KERNEL);
>>+	if (!zones) {
>>+		ret = -ENOMEM;
>>+		goto out;
>>+	}
>>+
>>+	/* Get zones type */
>>+	while (sector < nr_sectors) {
>>+		nr_zones = BTRFS_REPORT_NR_ZONES;
>>+		ret = btrfs_get_dev_zones(device, sector << SECTOR_SHIFT, zones,
>>+					  &nr_zones);
>>+		if (ret)
>>+			goto out;
>>+
>>+		for (i = 0; i < nr_zones; i++) {
>>+			if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ)
>>+				set_bit(nreported, zone_info->seq_zones);
>>+			if (zones[i].cond == BLK_ZONE_COND_EMPTY)
>>+				set_bit(nreported, zone_info->empty_zones);
>>+			nreported++;
>>+		}
>>+		sector = zones[nr_zones - 1].start + zones[nr_zones - 1].len;
>>+	}
>>+
>>+	if (nreported != zone_info->nr_zones) {
>>+		btrfs_err_in_rcu(device->fs_info,
>>+				 "inconsistent number of zones on %s (%u / %u)",
>>+				 rcu_str_deref(device->name), nreported,
>>+				 zone_info->nr_zones);
>>+		ret = -EIO;
>>+		goto out;
>>+	}
>>+
>>+	kfree(zones);
>>+
>>+	device->zone_info = zone_info;
>>+
>>+	devstr[0] = 0;
>>+	if (device->fs_info)
>>+		snprintf(devstr, sizeof(devstr), " (device %s)",
>>+			 device->fs_info->sb->s_id);
>>+
>>+	rcu_read_lock();
>>+	pr_info(
>
>Why isn't this btrfs_info() ?  Thanks,

Because, we might not have device->fs_info set at this point. At the mount
time, this function is called under btrfs_open_devices() in
btrfs_mount_root(). OTOH, device->fs_info is set under open_ctree() which
is called later than btrfs_open_devices().

Using btrfs_info() here results in printing "BTRFS info (device <unknown>):
..." at the mount time, which is an annoying look in my opinion. So, I
followed the "scanned by ..." message style in device_list_add().

I'll add a description comment here.