[PATCH RFC 2/2] btrfs-progs: add readmirror policy

[Anand Jain <anand.jain@oracle.com>]

This sets the readmirror=<parm> as a btrfs.<attr> extentded attribute.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 props.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/props.c b/props.c
index 3a498bd9e904..1d1a2c7f9d14 100644
--- a/props.c
+++ b/props.c
@@ -178,6 +178,53 @@ out:
 	return ret;
 }
 
+static int prop_readmirror(enum prop_object_type type, const char *object,
+			   const char *name, const char *value)
+{
+	int fd;
+	int ret;
+	char buf[256] = {0};
+	char *xattr_name;
+	DIR *dirstream = NULL;
+
+	fd = open_file_or_dir3(object, &dirstream, value ? O_RDWR : O_RDONLY);
+	if (fd < 0) {
+		ret = -errno;
+		error("failed to open %s: %m", object);
+		return ret;
+	}
+
+	xattr_name = alloc_xattr_name(name);
+	if (IS_ERR(xattr_name)) {
+		error("failed to alloc xattr_name %s: %m", object);
+		return PTR_ERR(xattr_name);
+	}
+
+	ret = 0;
+	if (value) {
+		if (fsetxattr(fd, xattr_name, value, strlen(value), 0) < 0) {
+			ret = -errno;
+			error("failed to set readmirror for %s: %m", object);
+		}
+	} else {
+		if (fgetxattr(fd, xattr_name, buf, 256) < 0) {
+			if (errno != ENOATTR) {
+				ret = -errno;
+				error("failed to get readmirror for %s: %m",
+				      object);
+			}
+		} else {
+			fprintf(stdout, "readmirror=%.*s\n", (int) strlen(buf),
+				buf);
+		}
+	}
+
+	free(xattr_name);
+	close_file_or_dir(fd, dirstream);
+
+	return ret;
+}
+
 const struct prop_handler prop_handlers[] = {
 	{"ro", "Set/get read-only flag of subvolume.", 0, prop_object_subvol,
 	 prop_read_only},
@@ -185,5 +232,7 @@ const struct prop_handler prop_handlers[] = {
 	 prop_object_dev | prop_object_root, prop_label},
 	{"compression", "Set/get compression for a file or directory", 0,
 	 prop_object_inode, prop_compression},
+	{"readmirror", "set/get readmirror policy for filesystem", 0,
+	 prop_object_root, prop_readmirror},
 	{NULL, NULL, 0, 0, NULL}
 };
-- 
1.8.3.1