[PATCH v6 3/8] file-posix: introduce get_sysfs_str_val for device zoned model

[Sam Li]

Use sysfs attribute files to get the string value of device
zoned model. Then get_sysfs_zoned_model can convert it to
BlockZoneModel type in QEMU.

Signed-off-by: Sam Li <faithilikerun@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 block/file-posix.c               | 70 ++++++++++++++++++++++++++++++++
 include/block/block_int-common.h |  3 ++
 2 files changed, 73 insertions(+)

diff --git a/block/file-posix.c b/block/file-posix.c
index a40eab64a2..4785203eea 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1264,6 +1264,68 @@ out:
 #endif
 }
 
+/*
+ * Convert the zoned attribute file in sysfs to internal value.
+ */
+static int get_sysfs_str_val(int fd, struct stat *st,
+                              const char *attribute,
+                              char **val) {
+#ifdef CONFIG_LINUX
+    char *buf = NULL;
+    g_autofree char *sysfspath = NULL;
+    int ret;
+    size_t len;
+
+    if (!S_ISBLK(st->st_mode)) {
+        return -ENOTSUP;
+    }
+
+    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/%s",
+                                major(st->st_rdev), minor(st->st_rdev),
+                                attribute);
+    ret = g_file_get_contents(sysfspath, &buf, &len, NULL);
+    if (ret == -1) {
+        ret = -errno;
+        return ret;
+    }
+
+    /* The file is ended with '\n' */
+    if (buf[len - 1] == '\n') {
+        buf[len - 1] = '\0';
+    }
+
+    if (!strncpy(*val, buf, len)) {
+        ret = -errno;
+        return ret;
+    }
+    g_free(buf);
+    return 0;
+#else
+    return -ENOTSUP;
+#endif
+}
+
+static int get_sysfs_zoned_model(int fd, struct stat *st,
+                                 BlockZoneModel *zoned) {
+    g_autofree char *val = NULL;
+    val = g_malloc(32);
+    get_sysfs_str_val(fd, st, "zoned", &val);
+    if (!val) {
+        return -ENOTSUP;
+    }
+
+    if (strcmp(val, "host-managed") == 0) {
+        *zoned = BLK_Z_HM;
+    } else if (strcmp(val, "host-aware") == 0) {
+        *zoned = BLK_Z_HA;
+    } else if (strcmp(val, "none") == 0) {
+        *zoned = BLK_Z_NONE;
+    } else {
+        return -ENOTSUP;
+    }
+    return 0;
+}
+
 static int hdev_get_max_segments(int fd, struct stat *st) {
     int ret;
     if (S_ISCHR(st->st_mode)) {
@@ -1279,6 +1341,8 @@ static void raw_refresh_limits(BlockDriverState *bs, 
Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     struct stat st;
+    int ret;
+    BlockZoneModel zoned;
 
     s->needs_alignment = raw_needs_alignment(bs);
     raw_probe_alignment(bs, s->fd, errp);
@@ -1316,6 +1380,12 @@ static void raw_refresh_limits(BlockDriverState *bs, 
Error **errp)
             bs->bl.max_hw_iov = ret;
         }
     }
+
+    ret = get_sysfs_zoned_model(s->fd, &st, &zoned);
+    if (ret < 0) {
+        zoned = BLK_Z_NONE;
+    }
+    bs->bl.zoned = zoned;
 }
 
 static int check_for_dasd(int fd)
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 8947abab76..7f7863cc9e 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -825,6 +825,9 @@ typedef struct BlockLimits {
 
     /* maximum number of iovec elements */
     int max_iov;
+
+    /* device zone model */
+    BlockZoneModel zoned;
 } BlockLimits;
 
 typedef struct BdrvOpBlocker BdrvOpBlocker;
-- 
2.37.1