diff --git a/src/os/unix/ngx_files.c b/src/os/unix/ngx_files.c
index 1203989..98ed082 100644
--- a/src/os/unix/ngx_files.c
+++ b/src/os/unix/ngx_files.c
@@ -416,3 +416,50 @@
 }
 
 #endif
+
+
+#if (NGX_HAVE_STATFS)
+
+size_t
+ngx_fs_bsize(u_char *name)
+{
+    struct statfs  fs;
+
+    if (statfs((char *) name, &fs) == -1) {
+        return 512;
+    }
+
+    if ((fs.f_bsize % 512) != 0) {
+        return 512;
+    }
+
+    return (size_t) fs.f_bsize;
+}
+
+#elif (NGX_HAVE_STATVFS)
+
+size_t
+ngx_fs_bsize(u_char *name)
+{
+    struct statvfs  fs;
+
+    if (statvfs((char *) name, &fs) == -1) {
+        return 512;
+    }
+
+    if ((fs.f_frsize % 512) != 0) {
+        return 512;
+    }
+
+    return (size_t) fs.f_frsize;
+}
+
+#else
+
+size_t
+ngx_fs_bsize(u_char *name)
+{
+    return 512;
+}
+
+#endif
diff --git a/src/os/unix/ngx_files.h b/src/os/unix/ngx_files.h
index 21e5ff4..dcd14c3 100644
--- a/src/os/unix/ngx_files.h
+++ b/src/os/unix/ngx_files.h
@@ -274,4 +274,7 @@
 #endif
 
 
+size_t ngx_fs_bsize(u_char *name);
+
+
 #endif /* _NGX_FILES_H_INCLUDED_ */
diff --git a/src/os/unix/ngx_freebsd_config.h b/src/os/unix/ngx_freebsd_config.h
index 24dcdcb..3771486 100644
--- a/src/os/unix/ngx_freebsd_config.h
+++ b/src/os/unix/ngx_freebsd_config.h
@@ -22,6 +22,7 @@
 #include <grp.h>
 #include <dirent.h>
 #include <glob.h>
+#include <sys/mount.h>          /* statfs() */
 
 #include <sys/filio.h>          /* FIONBIO */
 #include <sys/uio.h>
diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index bf2eae8..abeda08 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -28,6 +28,7 @@
 #include <grp.h>
 #include <dirent.h>
 #include <glob.h>
+#include <sys/vfs.h>            /* statfs() */
 
 #include <sys/uio.h>
 #include <sys/stat.h>
diff --git a/src/os/unix/ngx_posix_config.h b/src/os/unix/ngx_posix_config.h
index ec7ee94..152e232 100644
--- a/src/os/unix/ngx_posix_config.h
+++ b/src/os/unix/ngx_posix_config.h
@@ -44,6 +44,12 @@
 #include <grp.h>
 #include <dirent.h>
 #include <glob.h>
+#if (NGX_HAVE_SYS_MOUNT_H)
+#include <sys/mount.h>          /* statfs() */
+#endif
+#if (NGX_HAVE_SYS_STATVFS_H)
+#include <sys/statvfs.h>        /* statvfs() */
+#endif
 
 #if (NGX_HAVE_SYS_FILIO_H)
 #include <sys/filio.h>          /* FIONBIO */
diff --git a/src/os/unix/ngx_solaris_config.h b/src/os/unix/ngx_solaris_config.h
index 989a30e..663f265 100644
--- a/src/os/unix/ngx_solaris_config.h
+++ b/src/os/unix/ngx_solaris_config.h
@@ -28,6 +28,7 @@
 #include <grp.h>
 #include <dirent.h>
 #include <glob.h>
+#include <sys/statvfs.h>        /* statvfs() */
 
 #include <sys/filio.h>          /* FIONBIO */
 #include <sys/uio.h>
diff --git a/src/os/win32/ngx_files.c b/src/os/win32/ngx_files.c
index eff843a..afe31b9 100644
--- a/src/os/win32/ngx_files.c
+++ b/src/os/win32/ngx_files.c
@@ -504,8 +504,28 @@
     return 0;
 }
 
+
 ngx_int_t
 ngx_directio_off(ngx_fd_t fd)
 {
     return 0;
 }
+
+
+size_t
+ngx_fs_bsize(u_char *name)
+{
+    u_char  root[4];
+    u_long  sc, bs, nfree, ncl;
+
+    if (name[2] == ':') {
+        ngx_cpystrn(root, name, 4);
+        name = root;
+    }
+
+    if (GetDiskFreeSpace((const char *) name, &sc, &bs, &nfree, &ncl) == 0) {
+        return 512;
+    }
+
+    return sc * bs;
+}
diff --git a/src/os/win32/ngx_files.h b/src/os/win32/ngx_files.h
index b848792..47a7661 100644
--- a/src/os/win32/ngx_files.h
+++ b/src/os/win32/ngx_files.h
@@ -243,5 +243,7 @@
 ngx_int_t ngx_directio_off(ngx_fd_t fd);
 #define ngx_directio_off_n          "ngx_directio_off_n"
 
+size_t ngx_fs_bsize(u_char *name);
+
 
 #endif /* _NGX_FILES_H_INCLUDED_ */