[PATCH 1/3] hostmem: Detect and cache fs type for file hostmem

[Peter Xu <peterx@redhat.com>]

Detect the file system for a memory-backend-file object and cache it within
the object if possible when CONFIG_LINUX (using statfs).

Only support the two important types of memory (tmpfs, hugetlbfs) and keep
the rest as "unknown" for now.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 backends/hostmem-file.c  | 37 ++++++++++++++++++++++++++++++++++++-
 include/sysemu/hostmem.h |  1 +
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 25141283c4..2484e45a11 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -18,13 +18,17 @@
 #include "sysemu/hostmem.h"
 #include "qom/object_interfaces.h"
 #include "qom/object.h"
+#ifdef CONFIG_LINUX
+#include <sys/vfs.h>
+#include <linux/magic.h>
+#endif
 
 OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendFile, MEMORY_BACKEND_FILE)
 
 
 struct HostMemoryBackendFile {
     HostMemoryBackend parent_obj;
-
+    __fsword_t fs_type;
     char *mem_path;
     uint64_t align;
     bool discard_data;
@@ -52,6 +56,15 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         return;
     }
 
+#ifdef CONFIG_LINUX
+    struct statfs fs;
+    if (!statfs(fb->mem_path, &fs)) {
+        fb->fs_type = fs.f_type;
+    } else {
+        fb->fs_type = 0;
+    }
+#endif
+
     name = host_memory_backend_get_name(backend);
     ram_flags = backend->share ? RAM_SHARED : 0;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
@@ -181,6 +194,28 @@ static void file_backend_unparent(Object *obj)
     }
 }
 
+const char *file_memory_backend_get_fs_type(Object *obj)
+{
+#ifdef CONFIG_LINUX
+    HostMemoryBackendFile *fb = (HostMemoryBackendFile *)
+        object_dynamic_cast(obj, TYPE_MEMORY_BACKEND_FILE);
+
+    if (!fb) {
+        goto out;
+    }
+
+    switch (fb->fs_type) {
+    case TMPFS_MAGIC:
+        return "tmpfs";
+    case HUGETLBFS_MAGIC:
+        return "hugetlbfs";
+    }
+
+out:
+#endif
+    return "unknown";
+}
+
 static void
 file_backend_class_init(ObjectClass *oc, void *data)
 {
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 39326f1d4f..0354cffa6b 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -81,5 +81,6 @@ void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped);
 bool host_memory_backend_is_mapped(HostMemoryBackend *backend);
 size_t host_memory_backend_pagesize(HostMemoryBackend *memdev);
 char *host_memory_backend_get_name(HostMemoryBackend *backend);
+const char *file_memory_backend_get_fs_type(Object *obj);
 
 #endif
-- 
2.39.1