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Message-Id: <20250524061320.370630-7-yukuai1@huaweicloud.com>
Date: Sat, 24 May 2025 14:13:03 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: hch@....de,
	xni@...hat.com,
	colyli@...nel.org,
	song@...nel.org,
	yukuai3@...wei.com
Cc: linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH 06/23] md/md-bitmap: add a new sysfs api bitmap_type

From: Yu Kuai <yukuai3@...wei.com>

The api will be used by mdadm to set bitmap_ops while creating new array
or assemble array, prepare to add a new bitmap.

Currently available options are:

cat /sys/block/md0/md/bitmap_type
none [bitmap]

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 Documentation/admin-guide/md.rst | 73 ++++++++++++++----------
 drivers/md/md.c                  | 96 ++++++++++++++++++++++++++++++--
 drivers/md/md.h                  |  2 +
 3 files changed, 135 insertions(+), 36 deletions(-)

diff --git a/Documentation/admin-guide/md.rst b/Documentation/admin-guide/md.rst
index 4ff2cc291d18..356d2a344f08 100644
--- a/Documentation/admin-guide/md.rst
+++ b/Documentation/admin-guide/md.rst
@@ -347,6 +347,49 @@ All md devices contain:
      active-idle
          like active, but no writes have been seen for a while (safe_mode_delay).
 
+  consistency_policy
+     This indicates how the array maintains consistency in case of unexpected
+     shutdown. It can be:
+
+     none
+       Array has no redundancy information, e.g. raid0, linear.
+
+     resync
+       Full resync is performed and all redundancy is regenerated when the
+       array is started after unclean shutdown.
+
+     bitmap
+       Resync assisted by a write-intent bitmap.
+
+     journal
+       For raid4/5/6, journal device is used to log transactions and replay
+       after unclean shutdown.
+
+     ppl
+       For raid5 only, Partial Parity Log is used to close the write hole and
+       eliminate resync.
+
+     The accepted values when writing to this file are ``ppl`` and ``resync``,
+     used to enable and disable PPL.
+
+  uuid
+     This indicates the UUID of the array in the following format:
+     xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+
+  bitmap_type
+     [RW] When read, this file will display the current and available
+     bitmap for this array. The currently active bitmap will be enclosed
+     in [] brackets. Writing an bitmap name or ID to this file will switch
+     control of this array to that new bitmap. Note that writing a new
+     bitmap for created array is forbidden.
+
+     none
+         No bitmap
+     bitmap
+         The default internal bitmap
+
+If bitmap_type is bitmap, then the md device will also contain:
+
   bitmap/location
      This indicates where the write-intent bitmap for the array is
      stored.
@@ -401,36 +444,6 @@ All md devices contain:
      once the array becomes non-degraded, and this fact has been
      recorded in the metadata.
 
-  consistency_policy
-     This indicates how the array maintains consistency in case of unexpected
-     shutdown. It can be:
-
-     none
-       Array has no redundancy information, e.g. raid0, linear.
-
-     resync
-       Full resync is performed and all redundancy is regenerated when the
-       array is started after unclean shutdown.
-
-     bitmap
-       Resync assisted by a write-intent bitmap.
-
-     journal
-       For raid4/5/6, journal device is used to log transactions and replay
-       after unclean shutdown.
-
-     ppl
-       For raid5 only, Partial Parity Log is used to close the write hole and
-       eliminate resync.
-
-     The accepted values when writing to this file are ``ppl`` and ``resync``,
-     used to enable and disable PPL.
-
-  uuid
-     This indicates the UUID of the array in the following format:
-     xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
-
-
 As component devices are added to an md array, they appear in the ``md``
 directory as new directories named::
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 311e52d5173d..4eb0c6effd5b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -672,13 +672,18 @@ static void active_io_release(struct percpu_ref *ref)
 
 static void no_op(struct percpu_ref *r) {}
 
-static void mddev_set_bitmap_ops(struct mddev *mddev, enum md_submodule_id id)
+static bool mddev_set_bitmap_ops(struct mddev *mddev)
 {
 	xa_lock(&md_submodule);
-	mddev->bitmap_ops = xa_load(&md_submodule, id);
+	mddev->bitmap_ops = xa_load(&md_submodule, mddev->bitmap_id);
 	xa_unlock(&md_submodule);
-	if (!mddev->bitmap_ops)
-		pr_warn_once("md: can't find bitmap id %d\n", id);
+
+	if (!mddev->bitmap_ops) {
+		pr_warn_once("md: can't find bitmap id %d\n", mddev->bitmap_id);
+		return false;
+	}
+
+	return true;
 }
 
 static void mddev_clear_bitmap_ops(struct mddev *mddev)
@@ -688,8 +693,10 @@ static void mddev_clear_bitmap_ops(struct mddev *mddev)
 
 int mddev_init(struct mddev *mddev)
 {
-	/* TODO: support more versions */
-	mddev_set_bitmap_ops(mddev, ID_BITMAP);
+	mddev->bitmap_id = ID_BITMAP;
+
+	if (!mddev_set_bitmap_ops(mddev))
+		return -EINVAL;
 
 	if (percpu_ref_init(&mddev->active_io, active_io_release,
 			    PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
@@ -4155,6 +4162,82 @@ new_level_store(struct mddev *mddev, const char *buf, size_t len)
 static struct md_sysfs_entry md_new_level =
 __ATTR(new_level, 0664, new_level_show, new_level_store);
 
+static ssize_t
+bitmap_type_show(struct mddev *mddev, char *page)
+{
+	struct md_submodule_head *head;
+	unsigned long i;
+	ssize_t len = 0;
+
+	if (mddev->bitmap_id == ID_BITMAP_NONE)
+		len += sprintf(page + len, "[none] ");
+	else
+		len += sprintf(page + len, "none ");
+
+	xa_lock(&md_submodule);
+	xa_for_each(&md_submodule, i, head) {
+		if (head->type != MD_BITMAP)
+			continue;
+
+		if (mddev->bitmap_id == head->id)
+			len += sprintf(page + len, "[%s] ", head->name);
+		else
+			len += sprintf(page + len, "%s ", head->name);
+	}
+	xa_unlock(&md_submodule);
+
+	len += sprintf(page + len, "\n");
+	return len;
+}
+
+static ssize_t
+bitmap_type_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	struct md_submodule_head *head;
+	enum md_submodule_id id;
+	unsigned long i;
+	int err;
+
+	if (mddev->bitmap_ops)
+		return -EBUSY;
+
+	err = kstrtoint(buf, 10, &id);
+	if (!err) {
+		if (id == ID_BITMAP_NONE) {
+			mddev->bitmap_id = id;
+			return len;
+		}
+
+		xa_lock(&md_submodule);
+		head = xa_load(&md_submodule, id);
+		xa_unlock(&md_submodule);
+
+		if (head && head->type == MD_BITMAP) {
+			mddev->bitmap_id = id;
+			return len;
+		}
+	}
+
+	if (cmd_match(buf, "none")) {
+		mddev->bitmap_id = ID_BITMAP_NONE;
+		return len;
+	}
+
+	xa_lock(&md_submodule);
+	xa_for_each(&md_submodule, i, head) {
+		if (head->type == MD_BITMAP && cmd_match(buf, head->name)) {
+			mddev->bitmap_id = head->id;
+			xa_unlock(&md_submodule);
+			return len;
+		}
+	}
+	xa_unlock(&md_submodule);
+	return -ENOENT;
+}
+
+static struct md_sysfs_entry md_bitmap_type =
+__ATTR(bitmap_type, 0664, bitmap_type_show, bitmap_type_store);
+
 static ssize_t
 layout_show(struct mddev *mddev, char *page)
 {
@@ -5719,6 +5802,7 @@ __ATTR(serialize_policy, S_IRUGO | S_IWUSR, serialize_policy_show,
 static struct attribute *md_default_attrs[] = {
 	&md_level.attr,
 	&md_new_level.attr,
+	&md_bitmap_type.attr,
 	&md_layout.attr,
 	&md_raid_disks.attr,
 	&md_uuid.attr,
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 13e3f9ce1b79..bf34c0a36551 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -40,6 +40,7 @@ enum md_submodule_id {
 	ID_CLUSTER,
 	ID_BITMAP,
 	ID_LLBITMAP,	/* TODO */
+	ID_BITMAP_NONE,
 };
 
 struct md_submodule_head {
@@ -565,6 +566,7 @@ struct mddev {
 	struct percpu_ref		writes_pending;
 	int				sync_checkers;	/* # of threads checking writes_pending */
 
+	enum md_submodule_id		bitmap_id;
 	void				*bitmap; /* the bitmap for the device */
 	struct bitmap_operations	*bitmap_ops;
 	struct {
-- 
2.39.2


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