Changeset 77064 in vbox for trunk/src/VBox/Additions/linux/sharedfolders

Timestamp:

Jan 30, 2019 8:04:25 PM (6 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

128510

Message:

linux/vboxsf: Optimization of small reads (<= 3/4 page size) by embedding the data buffer into the request. bugref:9172

File:

• trunk/src/VBox/Additions/linux/sharedfolders/regops.c (modified) (4 diffs)

trunk/src/VBox/Additions/linux/sharedfolders/regops.c

@@ -262 +262 @@
  * @param buf           the buffer
  * @param size          length of the buffer
- * @param off           offset within the file
+ * @param off           offset within the file (in/out).
  * @returns the number of read bytes on success, Linux error code otherwise
  */
-static ssize_t sf_reg_read(struct file *file, char *buf, size_t size,
-                           loff_t * off)
+static ssize_t sf_reg_read(struct file *file, char /*__user*/ *buf, size_t size,
+                           loff_t *off)
 {
         int err;
@@ -290 +290 @@
                 return 0;
 
-        tmp =
-            alloc_bounce_buffer(&tmp_size, &tmp_phys, size,
-                                __PRETTY_FUNCTION__);
+#ifndef VBOXSF_USE_DEPRECATED_VBGL_INTERFACE
+        /*
+         * For small requests, try use an embedded buffer provided we get a heap block
+         * that does not cross page boundraries (see host code).
+         */
+        if (size <= PAGE_SIZE / 4 * 3 /* see allocator */) {
+                uint32_t const         cbReq = RT_UOFFSETOF(VBOXSFREADEMBEDDEDREQ, abData[0]) + size;
+                VBOXSFREADEMBEDDEDREQ *pReq  = (VBOXSFREADEMBEDDEDREQ *)VbglR0PhysHeapAlloc(cbReq);
+                if (   pReq
+                    && (PAGE_SIZE - ((uintptr_t)pReq & PAGE_OFFSET_MASK)) >= cbReq) {
+                        ssize_t cbRet;
+                        int vrc = VbglR0SfHostReqReadEmbedded(sf_g->map.root, pReq, sf_r->handle, pos, (uint32_t)size);
+                        if (RT_SUCCESS(vrc)) {
+                                cbRet = pReq->Parms.cb32Read.u.value32;
+                                if (copy_to_user(buf, pReq->abData, cbRet) == 0)
+                                        *off += cbRet;
+                                else
+                                        cbRet = -EPROTO;
+                        } else
+                                cbRet = -EPROTO;
+                        VbglR0PhysHeapFree(pReq);
+                        return cbRet;
+                }
+                if (pReq)
+                        VbglR0PhysHeapFree(pReq);
+        }
+
+//      /*
+//       * For other requests, use a bounce buffer.
+//       */
+//      VBOXSFREADPGLSTREQ *pReq  = (VBOXSFREADEMBEDDEDREQ *)VbglR0PhysHeapAlloc(cbReq);
+#endif
+
+        tmp = alloc_bounce_buffer(&tmp_size, &tmp_phys, size, __PRETTY_FUNCTION__);
         if (!tmp)
                 return -ENOMEM;
@@ -787 +818 @@
         uint32_t nread = PAGE_SIZE;
         char *buf;
-        loff_t off = ((loff_t) page->index) << PAGE_SHIFT;
+        loff_t off = (loff_t)page->index << PAGE_SHIFT;
         int ret;
 
@@ -876 +907 @@
 
         buf = kmap(page);
-        err =
-            sf_reg_write_aux(__func__, sf_g, sf_r, buf + from, &nwritten, pos);
+        err = sf_reg_write_aux(__func__, sf_g, sf_r, buf + from, &nwritten, pos);
         kunmap(page);