[v3,09/10] btrfs: enable RAID1 balancing configuration via modprobe parameter

Commit Message

Anand Jain Nov. 15, 2024, 2:54 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 192k:
  $ modprobe btrfs raid1-balancing=round-robin:196608

- Set the round-robin balancing method with the default
`min_contiguous_read` of 256k:
  $ 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   | 29 +++++++++++++++++++++++++++++
 fs/btrfs/sysfs.h   |  5 +++++
 fs/btrfs/volumes.c |  5 ++++-
 4 files changed, 43 insertions(+), 1 deletion(-)

Patch

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d52f7f6e2de7..ecadc8e0dcfb 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2552,6 +2552,11 @@  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 50b8b8847dd4..50bc4b6cb821 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1307,11 +1307,28 @@  BTRFS_ATTR(, temp_fsid, btrfs_temp_fsid_show);
 
 #ifdef CONFIG_BTRFS_EXPERIMENTAL
 static const char * const btrfs_read_policy_name[] = { "pid", "round-robin", "devid" };
+
+/* 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]]");
+
 #else
 static const char * const btrfs_read_policy_name[] = { "pid" };
 #endif
 
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+enum btrfs_read_policy btrfs_read_policy_to_enum(const char *str, s64 *value)
+#else
 static enum btrfs_read_policy btrfs_read_policy_to_enum(const char *str, s64 *value)
+#endif
 {
 #ifdef CONFIG_BTRFS_EXPERIMENTAL
 	char *value_str;
@@ -1354,6 +1371,18 @@  static enum btrfs_read_policy btrfs_read_policy_to_enum(const char *str, s64 *va
 	return -EINVAL;
 }
 
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+int __init btrfs_raid1_balancing_init(void)
+{
+	if (btrfs_read_policy_to_enum(raid1_balancing, NULL) == -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..f0fb0c0c2f7d 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);
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+enum btrfs_read_policy btrfs_read_policy_to_enum(const char *str, s64 *value);
+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 90d84fb664aa..2b31fdffea08 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1327,11 +1327,14 @@  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
 	/* Set min_contiguous_read to a default 256kib */
 	fs_devices->min_contiguous_read = 256 * 1024;
 	fs_devices->read_devid = latest_dev->devid;
+	fs_devices->read_policy =
+		btrfs_read_policy_to_enum(btrfs_get_raid1_balancing(), NULL);
+#else
+	fs_devices->read_policy = BTRFS_READ_POLICY_PID;
 #endif
 
 	return 0;