Add
/sys/fs/btrfs/UUID/read_policy
attribute so that the read policy for the raid1 and raid10 chunks can be
tuned.
When this attribute is read, it shall show all available policies, and
the active policy is with in [ ], read_policy attribute can be written
using one of the items showed in the read.
For example:
cat /sys/fs/btrfs/UUID/read_policy
[by_pid]
echo by_pid > /sys/fs/btrfs/UUID/read_policy
echo -n by_pid > /sys/fs/btrfs/UUID/read_policy
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
v2: check input len before strip and kstrdup.
fs/btrfs/sysfs.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/volumes.h | 1 +
2 files changed, 67 insertions(+)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 18dac99188ce..5092a0a26241 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -642,6 +642,71 @@ static ssize_t btrfs_checksum_show(struct kobject *kobj,
BTRFS_ATTR(, checksum, btrfs_checksum_show);
+static const inline char *btrfs_read_policy_name(enum btrfs_read_policy_type type)
+{
+ switch (type) {
+ case BTRFS_READ_BY_PID:
+ return "by_pid";
+ default:
+ return "null";
+ }
+}
+
+static ssize_t btrfs_read_policy_show(struct kobject *kobj,
+ struct kobj_attribute *a, char *buf)
+{
+ int i;
+ ssize_t len = 0;
+ struct btrfs_fs_devices *fs_devices = to_fs_devs(kobj);
+
+ for (i = 0; i < BTRFS_NR_READ_POLICY_TYPE; i++) {
+ if (len)
+ len += snprintf(buf + len, PAGE_SIZE, " ");
+ if (fs_devices->read_policy == i)
+ len += snprintf(buf + len, PAGE_SIZE, "[%s]",
+ btrfs_read_policy_name(i));
+ else
+ len += snprintf(buf + len, PAGE_SIZE, "%s",
+ btrfs_read_policy_name(i));
+ }
+
+ len += snprintf(buf + len, PAGE_SIZE, "\n");
+
+ return len;
+}
+
+static ssize_t btrfs_read_policy_store(struct kobject *kobj,
+ struct kobj_attribute *a,
+ const char *buf, size_t len)
+{
+ int i;
+ char *stripped;
+ char *policy_name;
+ struct btrfs_fs_devices *fs_devices = to_fs_devs(kobj);
+
+ if (len > BTRFS_READ_POLICY_NAME_MAX)
+ return -EINVAL;
+
+ policy_name = kstrdup(buf, GFP_KERNEL);
+ if (!policy_name)
+ return -ENOMEM;
+
+ stripped = strstrip(policy_name);
+
+ for (i = 0; i < BTRFS_NR_READ_POLICY_TYPE; i++) {
+ if (strncmp(stripped, btrfs_read_policy_name(i),
+ strlen(stripped)) == 0) {
+ fs_devices->read_policy = i;
+ kfree(policy_name);
+ return len;
+ }
+ }
+
+ kfree(policy_name);
+ 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),
@@ -650,6 +715,7 @@ static ssize_t btrfs_checksum_show(struct kobject *kobj,
BTRFS_ATTR_PTR(, quota_override),
BTRFS_ATTR_PTR(, metadata_uuid),
BTRFS_ATTR_PTR(, checksum),
+ BTRFS_ATTR_PTR(, read_policy),
NULL,
};
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 401dc32e0caa..022271898e0f 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -211,6 +211,7 @@ struct btrfs_device {
BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
/* read_policy types */
+#define BTRFS_READ_POLICY_NAME_MAX 12
#define BTRFS_READ_POLICY_DEFAULT BTRFS_READ_BY_PID
enum btrfs_read_policy_type {
BTRFS_READ_BY_PID,
--
1.8.3.1
