misc/Btrfs/Allocator Hints/btrfs_allocator_hints-5.15.patch

From 60b52539b055332086a7e7da9da9cc1f4909f55a Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:04 +0200
Subject: [PATCH 1/4] btrfs: add flags to give an hint to the chunk allocator

Add the following flags to give an hint about which chunk should be
allocated in which a disk.
The following flags are created:

- BTRFS_DEV_ALLOCATION_PREFERRED_DATA
  preferred data chunk, but metadata chunk allowed
- BTRFS_DEV_ALLOCATION_PREFERRED_METADATA
  preferred metadata chunk, but data chunk allowed
- BTRFS_DEV_ALLOCATION_METADATA_ONLY
  only metadata chunk allowed
- BTRFS_DEV_ALLOCATION_DATA_ONLY
  only data chunk allowed

Signed-off-by: Goffredo Baroncelli <kreijack@inwid.it>
---
 include/uapi/linux/btrfs_tree.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index e1c4c732aabac2..a8e32ff44ab8b3 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -384,6 +384,20 @@ struct btrfs_key {
 	__u64 offset;
 } __attribute__ ((__packed__));
 
+/* dev_item.type */
+
+/* btrfs chunk allocation hints */
+#define BTRFS_DEV_ALLOCATION_MASK_BIT_COUNT	3
+/* preferred data chunk, but metadata chunk allowed */
+#define BTRFS_DEV_ALLOCATION_PREFERRED_DATA	(0ULL)
+/* preferred metadata chunk, but data chunk allowed */
+#define BTRFS_DEV_ALLOCATION_PREFERRED_METADATA	(1ULL)
+/* only metadata chunk are allowed */
+#define BTRFS_DEV_ALLOCATION_METADATA_ONLY	(2ULL)
+/* only data chunk allowed */
+#define BTRFS_DEV_ALLOCATION_DATA_ONLY		(3ULL)
+/* 5..7 are unused values */
+
 struct btrfs_dev_item {
 	/* the internal btrfs device id */
 	__le64 devid;

From ea05f0db64e8713b509a3ba18a47842080a7ed6a Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:05 +0200
Subject: [PATCH 2/4] btrfs: export dev_item.type in
 /sys/fs/btrfs/<uuid>/devinfo/<devid>/type

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 fs/btrfs/sysfs.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 25a6f587852be2..207675930c1158 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1570,6 +1570,16 @@ static ssize_t btrfs_devinfo_error_stats_show(struct kobject *kobj,
 }
 BTRFS_ATTR(devid, error_stats, btrfs_devinfo_error_stats_show);
 
+static ssize_t btrfs_devinfo_type_show(struct kobject *kobj,
+					    struct kobj_attribute *a, char *buf)
+{
+	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
+						   devid_kobj);
+
+	return scnprintf(buf, PAGE_SIZE, "0x%08llx\n", device->type);
+}
+BTRFS_ATTR(devid, type, btrfs_devinfo_type_show);
+
 /*
  * Information about one device.
  *
@@ -1582,6 +1592,7 @@ static struct attribute *devid_attrs[] = {
 	BTRFS_ATTR_PTR(devid, replace_target),
 	BTRFS_ATTR_PTR(devid, scrub_speed_max),
 	BTRFS_ATTR_PTR(devid, writeable),
+	BTRFS_ATTR_PTR(devid, type),
 	NULL
 };
 ATTRIBUTE_GROUPS(devid);

From 5af82dfcafa8ed103e29315436adf1eb3fa6044f Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:06 +0200
Subject: [PATCH 3/4] btrfs: change the DEV_ITEM 'type' field via sysfs

Signed-off-by: Kai Krakow <kai@kaishome.de>
---
 fs/btrfs/sysfs.c   | 56 +++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/volumes.c |  2 +-
 fs/btrfs/volumes.h |  3 ++-
 3 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 207675930c1158..722bf99cb0236a 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1578,7 +1578,61 @@ static ssize_t btrfs_devinfo_type_show(struct kobject *kobj,
 
 	return scnprintf(buf, PAGE_SIZE, "0x%08llx\n", device->type);
 }
-BTRFS_ATTR(devid, type, btrfs_devinfo_type_show);
+
+static ssize_t btrfs_devinfo_type_store(struct kobject *kobj,
+				 struct kobj_attribute *a,
+				 const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_root *root;
+	struct btrfs_device *device;
+	int ret;
+	struct btrfs_trans_handle *trans;
+
+	u64 type, prev_type;
+
+	device = container_of(kobj, struct btrfs_device, devid_kobj);
+	fs_info = device->fs_info;
+	if (!fs_info)
+		return -EPERM;
+
+	root = fs_info->chunk_root;
+	if (sb_rdonly(fs_info->sb))
+		return -EROFS;
+
+	ret = kstrtou64(buf, 0, &type);
+	if (ret < 0)
+		return -EINVAL;
+
+	/* for now, allow to touch only the 'allocation hint' bits */
+	if (type & ~((1 << BTRFS_DEV_ALLOCATION_MASK_BIT_COUNT) - 1))
+		return -EINVAL;
+
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	prev_type = device->type;
+	device->type = type;
+
+	ret = btrfs_update_device(trans, device);
+
+	if (ret < 0) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto abort;
+	}
+
+	ret = btrfs_commit_transaction(trans);
+	if (ret < 0)
+		goto abort;
+
+	return len;
+abort:
+	device->type = prev_type;
+	return  ret;
+}
+BTRFS_ATTR_RW(devid, type, btrfs_devinfo_type_show, btrfs_devinfo_type_store);
 
 /*
  * Information about one device.
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2ec3b8ac8fa357..f00cdedbbd11d8 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2773,7 +2773,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	return ret;
 }
 
-static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
+noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
 					struct btrfs_device *device)
 {
 	int ret;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2183361db614da..5b6861ae468900 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -581,5 +581,6 @@ int btrfs_bg_type_to_factor(u64 flags);
 const char *btrfs_bg_type_to_raid_name(u64 flags);
 int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info);
 int btrfs_repair_one_zone(struct btrfs_fs_info *fs_info, u64 logical);
-
+int btrfs_update_device(struct btrfs_trans_handle *trans,
+                                       struct btrfs_device *device);
 #endif

From 14a694d039fd11e59dd90aa7cbca4af1df54c146 Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:07 +0200
Subject: [PATCH 4/4] btrfs: add allocator_hint mode

When this mode is enabled, the chunk allocation policy is modified as
follow.

Each disk may have a different tag:
- BTRFS_DEV_ALLOCATION_PREFERRED_METADATA
- BTRFS_DEV_ALLOCATION_METADATA_ONLY
- BTRFS_DEV_ALLOCATION_DATA_ONLY
- BTRFS_DEV_ALLOCATION_PREFERRED_DATA (default)

Where:
- ALLOCATION_PREFERRED_X means that it is preferred to use this disk for
the X chunk type (the other type may be allowed when the space is low)
- ALLOCATION_X_ONLY means that it is used *only* for the X chunk type.
This means also that it is a preferred choice.

Each time the allocator allocates a chunk of type X , first it takes the
disks tagged as ALLOCATION_X_ONLY or ALLOCATION_PREFERRED_X; if the space
is not enough, it uses also the disks tagged as ALLOCATION_METADATA_ONLY;
if the space is not enough, it uses also the other disks, with the
exception of the one marked as ALLOCATION_PREFERRED_Y, where Y the other
type of chunk (i.e. not X).

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 fs/btrfs/volumes.c | 97 +++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/volumes.h |  1 +
 2 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f00cdedbbd11d8..e74f2126cdf992 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -179,6 +179,19 @@ enum btrfs_raid_types __attribute_const__ btrfs_bg_flags_to_raid_index(u64 flags
 	return BTRFS_RAID_SINGLE; /* BTRFS_BLOCK_GROUP_SINGLE */
 }
 
+#define BTRFS_DEV_ALLOCATION_MASK ((1ULL << \
+		BTRFS_DEV_ALLOCATION_MASK_BIT_COUNT) - 1)
+#define BTRFS_DEV_ALLOCATION_MASK_COUNT (1ULL << \
+		BTRFS_DEV_ALLOCATION_MASK_BIT_COUNT)
+
+static const char alloc_hint_map[BTRFS_DEV_ALLOCATION_MASK_COUNT] = {
+	[BTRFS_DEV_ALLOCATION_DATA_ONLY] = -1,
+	[BTRFS_DEV_ALLOCATION_PREFERRED_DATA] = 0,
+	[BTRFS_DEV_ALLOCATION_PREFERRED_METADATA] = 1,
+	[BTRFS_DEV_ALLOCATION_METADATA_ONLY] = 2,
+	/* the other values are set to 0 */
+};
+
 const char *btrfs_bg_type_to_raid_name(u64 flags)
 {
 	const int index = btrfs_bg_flags_to_raid_index(flags);
@@ -4938,13 +4951,18 @@ static int btrfs_add_system_chunk(struct btrfs_fs_info *fs_info,
 }
 
 /*
- * sort the devices in descending order by max_avail, total_avail
+ * sort the devices in descending order by alloc_hint,
+ * max_avail, total_avail
  */
 static int btrfs_cmp_device_info(const void *a, const void *b)
 {
 	const struct btrfs_device_info *di_a = a;
 	const struct btrfs_device_info *di_b = b;
 
+	if (di_a->alloc_hint > di_b->alloc_hint)
+		return -1;
+	if (di_a->alloc_hint < di_b->alloc_hint)
+		return 1;
 	if (di_a->max_avail > di_b->max_avail)
 		return -1;
 	if (di_a->max_avail < di_b->max_avail)
@@ -5107,6 +5125,8 @@ static int gather_device_info(struct btrfs_fs_devices *fs_devices,
 	int ndevs = 0;
 	u64 max_avail;
 	u64 dev_offset;
+	int hint;
+	int i;
 
 	/*
 	 * in the first pass through the devices list, we gather information
@@ -5159,16 +5179,91 @@ static int gather_device_info(struct btrfs_fs_devices *fs_devices,
 		devices_info[ndevs].max_avail = max_avail;
 		devices_info[ndevs].total_avail = total_avail;
 		devices_info[ndevs].dev = device;
+
+		if ((ctl->type & BTRFS_BLOCK_GROUP_DATA) &&
+		     (ctl->type & BTRFS_BLOCK_GROUP_METADATA)) {
+			/*
+			 * if mixed bg set all the alloc_hint
+			 * fields to the same value, so the sorting
+			 * is not affected
+			 */
+			devices_info[ndevs].alloc_hint = 0;
+		} else if (ctl->type & BTRFS_BLOCK_GROUP_DATA) {
+			hint = device->type & BTRFS_DEV_ALLOCATION_MASK;
+
+			/*
+			 * skip BTRFS_DEV_METADATA_ONLY disks
+			 */
+			if (hint == BTRFS_DEV_ALLOCATION_METADATA_ONLY)
+				continue;
+			/*
+			 * if a data chunk must be allocated,
+			 * sort also by hint (data disk
+			 * higher priority)
+			 */
+			devices_info[ndevs].alloc_hint = -alloc_hint_map[hint];
+		} else { /* BTRFS_BLOCK_GROUP_METADATA */
+			hint = device->type & BTRFS_DEV_ALLOCATION_MASK;
+
+			/*
+			 * skip BTRFS_DEV_DATA_ONLY disks
+			 */
+			if (hint == BTRFS_DEV_ALLOCATION_DATA_ONLY)
+				continue;
+			/*
+			 * if a data chunk must be allocated,
+			 * sort also by hint (metadata hint
+			 * higher priority)
+			 */
+			devices_info[ndevs].alloc_hint = alloc_hint_map[hint];
+		}
+
 		++ndevs;
 	}
 	ctl->ndevs = ndevs;
 
+	/*
+	 * no devices available
+	 */
+	if (!ndevs)
+		return 0;
+
 	/*
 	 * now sort the devices by hole size / available space
 	 */
 	sort(devices_info, ndevs, sizeof(struct btrfs_device_info),
 	     btrfs_cmp_device_info, NULL);
 
+	/*
+	 * select the minimum set of disks grouped by hint that
+	 * can host the chunk
+	 */
+	ndevs = 0;
+	while (ndevs < ctl->ndevs) {
+		hint = devices_info[ndevs++].alloc_hint;
+		while (ndevs < ctl->ndevs &&
+		       devices_info[ndevs].alloc_hint == hint)
+				ndevs++;
+		if (ndevs >= ctl->devs_min)
+			break;
+	}
+
+	BUG_ON(ndevs > ctl->ndevs);
+	ctl->ndevs = ndevs;
+
+	/*
+	 * the next layers require the devices_info ordered by
+	 * max_avail. If we are returing two (or more) different
+	 * group of alloc_hint, this is not always true. So sort
+	 * these gain.
+	 */
+
+	for (i = 0 ; i < ndevs ; i++)
+		devices_info[i].alloc_hint = 0;
+
+	sort(devices_info, ndevs, sizeof(struct btrfs_device_info),
+	     btrfs_cmp_device_info, NULL);
+
 	return 0;
 }
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 5b6861ae468900..1644d7c428a215 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -369,6 +369,7 @@ struct btrfs_device_info {
 	u64 dev_offset;
 	u64 max_avail;
 	u64 total_avail;
+	int alloc_hint;
 };
 
 struct btrfs_raid_attr {