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From: Anand Jain <anand.jain@oracle.com>
To: linux-btrfs@vger.kernel.org
Cc: josef@toxicpanda.com, btrfs-list@steev.me.uk
Subject: [PATCH 2/2] btrfs: sysfs, add read_policy attribute
Date: Sun,  5 Jan 2020 23:14:02 +0800	[thread overview]
Message-ID: <20200105151402.1440-3-anand.jain@oracle.com> (raw)
In-Reply-To: <20200105151402.1440-1-anand.jain@oracle.com>

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@oracle.com>
---
 fs/btrfs/sysfs.c   | 67 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h |  1 +
 2 files changed, 68 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index d414b98fb27f..ae2935184d75 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -642,6 +642,72 @@ 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);
+
+	policy_name = kstrdup(buf, GFP_KERNEL);
+	if (!policy_name)
+		return -ENOMEM;
+
+	stripped = strstrip(policy_name);
+	if (strlen(stripped) > BTRFS_READ_POLICY_NAME_MAX) {
+		kfree(policy_name);
+		return -EINVAL;
+	}
+
+	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 +716,7 @@ static const struct attribute *btrfs_attrs[] = {
 	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 3bbf0e51433f..dd8a8d2fbbe1 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -210,6 +210,7 @@ BTRFS_DEVICE_GETSET_FUNCS(disk_total_bytes);
 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,
-- 
2.23.0


  parent reply	other threads:[~2020-01-05 15:17 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-05 15:14 [PATCH v4 0/2] readmirror feature (sysfs and in-memory only approach) Anand Jain
2020-01-05 15:14 ` [PATCH 1/2] btrfs: add read_policy framework Anand Jain
2020-01-06 16:22   ` Josef Bacik
2020-01-29 18:26   ` David Sterba
2020-02-11  8:31     ` Anand Jain
2020-01-05 15:14 ` Anand Jain [this message]
2020-01-06 16:21   ` [PATCH 2/2] btrfs: sysfs, add read_policy attribute Josef Bacik
2020-01-07  4:52     ` [PATCH v2 " Anand Jain
2020-01-07 15:03       ` Josef Bacik
2020-01-07 15:25       ` Holger Hoffstätte
2020-01-08  4:16         ` [PATCH v3 " Anand Jain
2020-01-29 18:49           ` David Sterba
2020-02-12 14:24             ` Anand Jain
2020-01-29 18:07 ` [PATCH v4 0/2] readmirror feature (sysfs and in-memory only approach) David Sterba

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