diff --git a/mongoose.c b/mongoose.c
index 6428aadf..6c1b2950 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -495,10 +495,6 @@ bool mg_file_printf(struct mg_fs *fs, const char *path, const char *fmt, ...) {
 #if MG_ENABLE_FATFS
 #include <ff.h>
 
-#if !defined(MG_FATFS_ROOT)
-#define MG_FATFS_ROOT "/"
-#endif
-
 static int ff_stat(const char *path, size_t *size, time_t *mtime) {
   FILINFO fi;
   if (path[0] == '\0' || strcmp(path, MG_FATFS_ROOT) == 0) {
@@ -554,9 +550,14 @@ static size_t ff_read(void *fp, void *buf, size_t len) {
 }
 
 static size_t ff_write(void *fp, const void *buf, size_t len) {
-  unsigned n = 0;
-  f_write((FIL *) fp, buf, len, &n);
-  return n;
+  unsigned n, sum = 0, bs = MG_FATFS_BSIZE;
+  while ((size_t) sum < len &&
+         f_write((FIL *) fp, (char *) buf + sum,
+                 sum + bs > len ? len - sum : bs, &n) == FR_OK &&
+         n > 0) {
+    sum += n;
+  }
+  return sum;
 }
 
 static size_t ff_seek(void *fp, size_t offset) {
@@ -1865,9 +1866,9 @@ int mg_http_upload(struct mg_connection *c, struct mg_http_message *hm,
       mg_http_reply(c, 400, "", "open(%s): %d", path, errno);
       return -2;
     } else {
-      fs->write(fd->fd, hm->body.ptr, hm->body.len);
+      int written = (int) fs->write(fd->fd, hm->body.ptr, hm->body.len);
       mg_fs_close(fd);
-      mg_http_reply(c, 200, "", "");
+      mg_http_reply(c, 200, "", "%d", written);
       return (int) hm->body.len;
     }
   }
diff --git a/mongoose.h b/mongoose.h
index 82a06c62..b8650524 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -446,6 +446,14 @@ static __inline struct tm *localtime_r(const time_t *t, struct tm *tm) {
 #define MG_ENABLE_FATFS 0
 #endif
 
+#ifndef MG_FATFS_ROOT
+#define MG_FATFS_ROOT "/"
+#endif
+
+#ifndef MG_FATFS_BSIZE
+#define MG_FATFS_BSIZE 64
+#endif
+
 #ifndef MG_ENABLE_SOCKET
 #define MG_ENABLE_SOCKET 1
 #endif
@@ -626,7 +634,7 @@ struct mg_fs {
   size_t (*seek)(void *fd, size_t offset);                 // Set file position
   bool (*rename)(const char *from, const char *to);        // Rename
   bool (*remove)(const char *path);                        // Delete file
-  bool (*mkdir)(const char *path);                         // Create directory
+  bool (*mkd)(const char *path);                           // Create directory
 };
 
 // File descriptor
diff --git a/src/config.h b/src/config.h
index 8fbeba60..d1c637e6 100644
--- a/src/config.h
+++ b/src/config.h
@@ -4,6 +4,14 @@
 #define MG_ENABLE_FATFS 0
 #endif
 
+#ifndef MG_FATFS_ROOT
+#define MG_FATFS_ROOT "/"
+#endif
+
+#ifndef MG_FATFS_BSIZE
+#define MG_FATFS_BSIZE 64
+#endif
+
 #ifndef MG_ENABLE_SOCKET
 #define MG_ENABLE_SOCKET 1
 #endif
diff --git a/src/fs.h b/src/fs.h
index 70239b0e..c84c4ee5 100644
--- a/src/fs.h
+++ b/src/fs.h
@@ -18,7 +18,7 @@ struct mg_fs {
   size_t (*seek)(void *fd, size_t offset);                 // Set file position
   bool (*rename)(const char *from, const char *to);        // Rename
   bool (*remove)(const char *path);                        // Delete file
-  bool (*mkdir)(const char *path);                         // Create directory
+  bool (*mkd)(const char *path);                           // Create directory
 };
 
 // File descriptor
diff --git a/src/fs_fat.c b/src/fs_fat.c
index bf7e1ebf..bd1b5457 100644
--- a/src/fs_fat.c
+++ b/src/fs_fat.c
@@ -3,10 +3,6 @@
 #if MG_ENABLE_FATFS
 #include <ff.h>
 
-#if !defined(MG_FATFS_ROOT)
-#define MG_FATFS_ROOT "/"
-#endif
-
 static int ff_stat(const char *path, size_t *size, time_t *mtime) {
   FILINFO fi;
   if (path[0] == '\0' || strcmp(path, MG_FATFS_ROOT) == 0) {
@@ -62,9 +58,14 @@ static size_t ff_read(void *fp, void *buf, size_t len) {
 }
 
 static size_t ff_write(void *fp, const void *buf, size_t len) {
-  unsigned n = 0;
-  f_write((FIL *) fp, buf, len, &n);
-  return n;
+  unsigned n, sum = 0, bs = MG_FATFS_BSIZE;
+  while ((size_t) sum < len &&
+         f_write((FIL *) fp, (char *) buf + sum,
+                 sum + bs > len ? len - sum : bs, &n) == FR_OK &&
+         n > 0) {
+    sum += n;
+  }
+  return sum;
 }
 
 static size_t ff_seek(void *fp, size_t offset) {
diff --git a/src/http.c b/src/http.c
index a9276828..a9195d89 100644
--- a/src/http.c
+++ b/src/http.c
@@ -906,9 +906,9 @@ int mg_http_upload(struct mg_connection *c, struct mg_http_message *hm,
       mg_http_reply(c, 400, "", "open(%s): %d", path, errno);
       return -2;
     } else {
-      fs->write(fd->fd, hm->body.ptr, hm->body.len);
+      int written = (int) fs->write(fd->fd, hm->body.ptr, hm->body.len);
       mg_fs_close(fd);
-      mg_http_reply(c, 200, "", "");
+      mg_http_reply(c, 200, "", "%d", written);
       return (int) hm->body.len;
     }
   }