[Midnightbsd-cvs] src [7800] trunk/sys/fs/ext2fs/ext2_alloc.c: ext2fs fix

[laffer1 at midnightbsd.org]

Revision: 7800
          http://svnweb.midnightbsd.org/src/?rev=7800
Author:   laffer1
Date:     2016-09-05 15:36:58 -0400 (Mon, 05 Sep 2016)
Log Message:
-----------
ext2fs fix

While a file is first being written, the dynamic block reallocation realocates t
he file's blocks so as to cluster them together into a contiguous set of blocks
on the disk.

When the cluster crosses the boundary into the first indirect block, the first i
ndirect block is initially allocated in a position immediately following the las
t direct block. Block reallocation would usually destroy locality by moving the
indirect block of the way to keep the data blocks contiguous.

Obtained from: FreeBSD svn 243913

Modified Paths:
--------------
    trunk/sys/fs/ext2fs/ext2_alloc.c

Property Changed:
----------------
    trunk/sys/fs/ext2fs/ext2_alloc.c

Modified: trunk/sys/fs/ext2fs/ext2_alloc.c
===================================================================
--- trunk/sys/fs/ext2fs/ext2_alloc.c	2016-09-05 19:33:01 UTC (rev 7799)
+++ trunk/sys/fs/ext2fs/ext2_alloc.c	2016-09-05 19:36:58 UTC (rev 7800)
@@ -197,6 +197,18 @@
 			panic("ext2_reallocblks: non-cluster");
 #endif
 	/*
+	 * If the cluster crosses the boundary for the first indirect
+	 * block, leave space for the indirect block. Indirect blocks
+	 * are initially laid out in a position after the last direct
+	 * block. Block reallocation would usually destroy locality by
+	 * moving the indirect block out of the way to make room for
+	 * data blocks if we didn't compensate here. We should also do
+	 * this for other indirect block boundaries, but it is only
+	 * important for the first one.
+	 */
+	if (start_lbn < NDADDR && end_lbn >= NDADDR)
+		return (ENOSPC);
+	/*
 	 * If the latest allocation is in a new cylinder group, assume that
 	 * the filesystem has decided to move and do not force it back to
 	 * the previous cylinder group.


Property changes on: trunk/sys/fs/ext2fs/ext2_alloc.c
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Deleted: cvs2svn:cvs-rev
## -1 +0,0 ##
-1.2
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