From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Fri, 11 Mar 2011 22:31:26 +0000 (-0800)
Subject: Optimize overwrites of the last block of a file
X-Git-Url: http://git.vrable.net/?p=bluesky.git;a=commitdiff_plain;h=93d0310df9437763aa239f38372b62b9d0480de0

Optimize overwrites of the last block of a file
---

diff --git a/bluesky/file.c b/bluesky/file.c
index 72467f3..1936375 100644
--- a/bluesky/file.c
+++ b/bluesky/file.c
@@ -163,16 +163,17 @@ void bluesky_file_write(BlueSkyInode *inode, uint64_t offset,
     if (len == 0)
         return;
 
-    // TODO: Optimization: If we are entirely overwriting a block we don't need
-    // to fetch it frm storage first.  We don't yet handle the case where the
-    // partial last block of a file is entirely overwritten.
     while (len > 0) {
         uint64_t block_num = offset / BLUESKY_BLOCK_SIZE;
         gint block_offset = offset % BLUESKY_BLOCK_SIZE;
         gint bytes = MIN(BLUESKY_BLOCK_SIZE - block_offset, len);
 
         gboolean preserve = TRUE;
-        if (block_offset == 0 && bytes == BLUESKY_BLOCK_SIZE) {
+        gsize block_size = BLUESKY_BLOCK_SIZE;
+        if (block_num == inode->blocks->len - 1) {
+            block_size = inode->size - block_num * BLUESKY_BLOCK_SIZE;
+        }
+        if (block_offset == 0 && bytes == block_size) {
             preserve = FALSE;
         }
         bluesky_block_touch(inode, block_num, preserve);