[v5,09/10] btrfs: enable RAID1 balancing configuration via modprobe parameter

Commit Message

Anand Jain Jan. 1, 2025, 6:06 p.m. UTC

This update allows configuring the `raid1-balancing` methods using a
modprobe parameter when experimental mode CONFIG_BTRFS_EXPERIMENTAL
is enabled.

Examples:

- Set the RAID1 balancing method to round-robin with a custom
`min_contiguous_read` of 4k:
  $ modprobe btrfs raid1-balancing=round-robin:4096

- Set the round-robin balancing method with the default
`min_contiguous_read`:
  $ modprobe btrfs raid1-balancing=round-robin

- Set the `devid` balancing method, defaulting to the latest
device:
  $ modprobe btrfs raid1-balancing=devid

Signed-off-by: Anand Jain <[e-mail]>
---
 fs/btrfs/super.c   |  5 +++++
 fs/btrfs/sysfs.c   | 30 +++++++++++++++++++++++++++++-
 fs/btrfs/sysfs.h   |  5 +++++
 fs/btrfs/volumes.c | 14 +++++++++++++-
 4 files changed, 52 insertions(+), 2 deletions(-)

Patch

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index fb6a009c72ae..58190989a29d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2538,6 +2538,11 @@  static const struct init_sequence mod_init_seq[] = {
 	}, {
 		.init_func = extent_map_init,
 		.exit_func = extent_map_exit,
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+	}, {
+		.init_func = btrfs_raid1_balancing_init,
+		.exit_func = NULL,
+#endif
 	}, {
 		.init_func = ordered_data_init,
 		.exit_func = ordered_data_exit,
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index eb23f29995e4..ac1a32af2442 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1313,7 +1313,21 @@  static const char *btrfs_read_policy_name[] = {
 #endif
 };
 
-static int btrfs_read_policy_to_enum(const char *str, s64 *value)
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+/* Global module configuration parameters */
+static char *raid1_balancing;
+char *btrfs_get_raid1_balancing(void)
+{
+	return raid1_balancing;
+}
+
+/* Set perm 0, disable sys/module/btrfs/parameter/raid1_balancing interface */
+module_param(raid1_balancing, charp, 0);
+MODULE_PARM_DESC(raid1_balancing,
+"Global read policy; pid (default), round-robin[:min_contiguous_read], devid[[:devid]|[:latest-gen]|[:oldest-gen]]");
+#endif
+
+int btrfs_read_policy_to_enum(const char *str, s64 *value)
 {
 	char param[32] = {'\0'};
 	char *__maybe_unused value_str;
@@ -1336,6 +1350,20 @@  static int btrfs_read_policy_to_enum(const char *str, s64 *value)
 	return sysfs_match_string(btrfs_read_policy_name, param);
 }
 
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+int __init btrfs_raid1_balancing_init(void)
+{
+	s64 value;
+
+	if (btrfs_read_policy_to_enum(raid1_balancing, &value) == -EINVAL) {
+		btrfs_err(NULL, "Invalid raid1_balancing %s", raid1_balancing);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#endif
+
 static ssize_t btrfs_read_policy_show(struct kobject *kobj,
 				      struct kobj_attribute *a, char *buf)
 {
diff --git a/fs/btrfs/sysfs.h b/fs/btrfs/sysfs.h
index e6a284c59809..e97d383b9ffc 100644
--- a/fs/btrfs/sysfs.h
+++ b/fs/btrfs/sysfs.h
@@ -47,5 +47,10 @@  void btrfs_sysfs_del_qgroups(struct btrfs_fs_info *fs_info);
 int btrfs_sysfs_add_qgroups(struct btrfs_fs_info *fs_info);
 void btrfs_sysfs_del_one_qgroup(struct btrfs_fs_info *fs_info,
 				struct btrfs_qgroup *qgroup);
+int btrfs_read_policy_to_enum(const char *str, s64 *value);
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+int __init btrfs_raid1_balancing_init(void);
+char *btrfs_get_raid1_balancing(void);
+#endif
 
 #endif
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e8cccfad6ad3..e5e9b33837b8 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1299,6 +1299,7 @@  static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 	struct btrfs_device *device;
 	struct btrfs_device *latest_dev = NULL;
 	struct btrfs_device *tmp_device;
+	s64 __maybe_unused value = 0;
 	int ret = 0;
 
 	/* Initialize the in-memory record of filesystem read count */
@@ -1333,10 +1334,21 @@  static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 	fs_devices->latest_dev = latest_dev;
 	fs_devices->total_rw_bytes = 0;
 	fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_REGULAR;
-	fs_devices->read_policy = BTRFS_READ_POLICY_PID;
 #ifdef CONFIG_BTRFS_EXPERIMENTAL
 	fs_devices->rr_min_contiguous_read = BTRFS_DEFAULT_RR_MIN_CONTIGUOUS_READ;
 	fs_devices->read_devid = latest_dev->devid;
+	fs_devices->read_policy =
+		btrfs_read_policy_to_enum(btrfs_get_raid1_balancing(), &value);
+	if (fs_devices->read_policy == BTRFS_READ_POLICY_RR)
+		fs_devices->fs_stats = true;
+	if (value) {
+		if (fs_devices->read_policy == BTRFS_READ_POLICY_RR)
+			fs_devices->rr_min_contiguous_read = value;
+		if (fs_devices->read_policy == BTRFS_READ_POLICY_DEVID)
+			fs_devices->read_devid = value;
+	}
+#else
+	fs_devices->read_policy = BTRFS_READ_POLICY_PID;
 #endif
 
 	return 0;