Use more precise stat.st_blocks to account cache size on Unix
instead of file length rounded to a file system block size.
There is no similar way on Windows, so rounding to a cache->bsize is kept.

src/core/ngx_open_file_cache.c

diff --git a/src/core/ngx_open_file_cache.c b/src/core/ngx_open_file_cache.c
index a9c4532..a70385c 100644
--- a/src/core/ngx_open_file_cache.c
+++ b/src/core/ngx_open_file_cache.c
@@ -155,6 +155,7 @@
             of->uniq = ngx_file_uniq(&fi);
             of->mtime = ngx_file_mtime(&fi);
             of->size = ngx_file_size(&fi);
+            of->fs_size = ngx_file_fs_size(&fi);
             of->is_dir = ngx_is_dir(&fi);
             of->is_file = ngx_is_file(&fi);
             of->is_link = ngx_is_link(&fi);
@@ -557,6 +558,7 @@
     of->uniq = ngx_file_uniq(&fi);
     of->mtime = ngx_file_mtime(&fi);
     of->size = ngx_file_size(&fi);
+    of->fs_size = ngx_file_fs_size(&fi);
     of->is_dir = ngx_is_dir(&fi);
     of->is_file = ngx_is_file(&fi);
     of->is_link = ngx_is_link(&fi);

src/core/ngx_open_file_cache.h

diff --git a/src/core/ngx_open_file_cache.h b/src/core/ngx_open_file_cache.h
index f56dfcc..638bc5d 100644
--- a/src/core/ngx_open_file_cache.h
+++ b/src/core/ngx_open_file_cache.h
@@ -20,6 +20,7 @@
     ngx_file_uniq_t          uniq;
     time_t                   mtime;
     off_t                    size;
+    off_t                    fs_size;
     off_t                    directio;
     size_t                   read_ahead;