[Qemu-devel] [PATCH 2/4] raw: Recognize zoned backing devices

[Dmitry Fomichev <dmitry.fomichev@wdc.com>]

The purpose of this patch is to recognize a zoned block device (ZBD)
when it is opened as a raw file. The new code initializes the zoned
model propery introduced by the previous commit.

This commit is Linux-specific and in essence it checks the Zoned
Block Device Model (None/Host-managed/Host-aware) value in sysfs on
the host.

In order to avoid code duplication in file-posix.c, a common helper
function is added to read value of a sysfs entry under
/sys/block/<dev>/queue. Now, the existing function that reads the
"max_segments" value and the the new function that reads "zoned"
value share the same helper code.

Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
---
 block/file-posix.c | 69 ++++++++++++++++++++++++++++++++++++++--------
 block/raw-format.c |  8 ++++++
 2 files changed, 66 insertions(+), 11 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index ab05b51a66..dd81dc3301 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1055,33 +1055,53 @@ static int hdev_get_max_transfer_length(BlockDriverState *bs, int fd)
 #endif
 }
 
-static int hdev_get_max_segments(const struct stat *st)
+static int hdev_read_blk_queue_entry(const struct stat *st, const char *key,
+    char *buf, int buf_len)
 {
 #ifdef CONFIG_LINUX
-    char buf[32];
-    const char *end;
     char *sysfspath;
     int ret;
     int fd = -1;
-    long max_segments;
 
-    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments",
-                                major(st->st_rdev), minor(st->st_rdev));
+    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/%s",
+                                major(st->st_rdev), minor(st->st_rdev), key);
     fd = open(sysfspath, O_RDONLY);
     if (fd == -1) {
         ret = -errno;
         goto out;
     }
     do {
-        ret = read(fd, buf, sizeof(buf) - 1);
+        ret = read(fd, buf, buf_len - 1);
     } while (ret == -1 && errno == EINTR);
     if (ret < 0) {
         ret = -errno;
-        goto out;
     } else if (ret == 0) {
         ret = -EIO;
+    }
+out:
+    if (fd != -1) {
+        close(fd);
+    }
+    g_free(sysfspath);
+    return ret;
+#else
+    return -ENOTSUP;
+#endif
+}
+
+static int hdev_get_max_segments(const struct stat *st)
+{
+#ifdef CONFIG_LINUX
+    char buf[32];
+    const char *end;
+    int ret;
+    long max_segments;
+
+    ret = hdev_read_blk_queue_entry(st, "max_segments", buf, sizeof(buf));
+    if (ret < 0) {
         goto out;
     }
+
     buf[ret] = 0;
     /* The file is ended with '\n', pass 'end' to accept that. */
     ret = qemu_strtol(buf, &end, 10, &max_segments);
@@ -1090,10 +1110,33 @@ static int hdev_get_max_segments(const struct stat *st)
     }
 
 out:
-    if (fd != -1) {
-        close(fd);
+    return ret;
+#else
+    return -ENOTSUP;
+#endif
+}
+
+static int hdev_get_zoned_model(const struct stat *st)
+{
+#ifdef CONFIG_LINUX
+    char buf[32];
+    int ret;
+
+    ret = hdev_read_blk_queue_entry(st, "zoned", buf, sizeof(buf));
+    if (ret < 0) {
+        ret = BLK_ZONED_NONE;
+        goto out;
     }
-    g_free(sysfspath);
+
+    buf[ret - 1] = 0;
+    ret = BLK_ZONED_NONE;
+    if (strcmp(buf, "host-managed") == 0) {
+        ret = BLK_ZONED_HM;
+    } else if (strcmp(buf, "host-aware") == 0) {
+        ret = BLK_ZONED_HA;
+    }
+
+out:
     return ret;
 #else
     return -ENOTSUP;
@@ -1116,6 +1159,10 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
                 bs->bl.max_transfer = MIN(bs->bl.max_transfer,
                                           ret * getpagesize());
             }
+            ret = hdev_get_zoned_model(&st);
+            if (ret >= 0) {
+                bs->bl.zoned_model = ret;
+            }
         }
     }
 
diff --git a/block/raw-format.c b/block/raw-format.c
index bffd424dd0..12c2a3f95d 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -369,6 +369,13 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
     }
 }
 
+static void raw_get_zoned_info(BlockDriverState *bs)
+{
+    if (!bs->probed) {
+        bs->bl.zoned_model = bs->file->bs->bl.zoned_model;
+    }
+}
+
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         PreallocMode prealloc, Error **errp)
 {
@@ -572,6 +579,7 @@ BlockDriver bdrv_raw = {
     .bdrv_co_ioctl        = &raw_co_ioctl,
     .create_opts          = &raw_create_opts,
     .bdrv_has_zero_init   = &raw_has_zero_init,
+    .bdrv_get_zoned_info  = &raw_get_zoned_info,
     .strong_runtime_opts  = raw_strong_runtime_opts,
     .mutable_opts         = mutable_opts,
 };
-- 
2.21.0