diff mbox series

[v10,3/3] btrfs: create read policy sysfs attribute, pid

Message ID 6ce8b8a1d7b87c213f763fc59259eb08740a11f6.1603858308.git.anand.jain@oracle.com (mailing list archive)
State New, archived
Headers show
Series readmirror feature (read_policy sysfs and in-memory only approach) | expand

Commit Message

Anand Jain Oct. 28, 2020, 4:25 a.m. UTC 
Add

 /sys/fs/btrfs/UUID/read_policy

attribute so that the read policy for the raid1, raid1c34 and raid10 can
be tuned.

When this attribute is read, it shall show all available policies, with
active policy being with in [ ]. The read_policy attribute can be written
using one of the items listed in there.

For example:
  $cat /sys/fs/btrfs/UUID/read_policy
  [pid]
  $echo pid > /sys/fs/btrfs/UUID/read_policy

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
v10: use scnprintf instead of snprintf
v9: fix C coding style, static const char*
v5: 
  Title rename: old: btrfs: sysfs, add read_policy attribute
  Uses the btrfs_strmatch() helper (BTRFS_READ_POLICY_NAME_MAX dropped).
  Use the table for the policy names.
  Rename len to ret.
  Use a simple logic to prefix space in btrfs_read_policy_show()
  Reviewed-by: Josef Bacik <josef@toxicpanda.com> dropped.

v4:-
v3: rename [by_pid] to [pid]
v2: v2: check input len before strip and kstrdup

 fs/btrfs/sysfs.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
diff mbox series

Patch

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 2e114f5181e8..ef90b9cc1d5d 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -872,6 +872,54 @@  static bool btrfs_strmatch(const char *given, const char *golden)
 	return false;
 }
 
+static const char * const btrfs_read_policy_name[] = { "pid" };
+
+static ssize_t btrfs_read_policy_show(struct kobject *kobj,
+				      struct kobj_attribute *a, char *buf)
+{
+	int i;
+	ssize_t ret = 0;
+	struct btrfs_fs_devices *fs_devices = to_fs_devs(kobj);
+
+	for (i = 0; i < BTRFS_NR_READ_POLICY; i++) {
+		if (fs_devices->read_policy == i)
+			ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s[%s]",
+					 (ret == 0 ? "" : " "),
+					 btrfs_read_policy_name[i]);
+		else
+			ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
+					 (ret == 0 ? "" : " "),
+					 btrfs_read_policy_name[i]);
+	}
+
+	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+
+	return ret;
+}
+
+static ssize_t btrfs_read_policy_store(struct kobject *kobj,
+				       struct kobj_attribute *a,
+				       const char *buf, size_t len)
+{
+	int i;
+	struct btrfs_fs_devices *fs_devices = to_fs_devs(kobj);
+
+	for (i = 0; i < BTRFS_NR_READ_POLICY; i++) {
+		if (btrfs_strmatch(buf, btrfs_read_policy_name[i])) {
+			if (i != fs_devices->read_policy) {
+				fs_devices->read_policy = i;
+				btrfs_info(fs_devices->fs_info,
+					   "read policy set to '%s'",
+					   btrfs_read_policy_name[i]);
+			}
+			return len;
+		}
+	}
+
+	return -EINVAL;
+}
+BTRFS_ATTR_RW(, read_policy, btrfs_read_policy_show, btrfs_read_policy_store);
+
 static const struct attribute *btrfs_attrs[] = {
 	BTRFS_ATTR_PTR(, label),
 	BTRFS_ATTR_PTR(, nodesize),
@@ -881,6 +929,7 @@  static const struct attribute *btrfs_attrs[] = {
 	BTRFS_ATTR_PTR(, metadata_uuid),
 	BTRFS_ATTR_PTR(, checksum),
 	BTRFS_ATTR_PTR(, exclusive_operation),
+	BTRFS_ATTR_PTR(, read_policy),
 	NULL,
 };