[syslinux:master] extlinux/main.c: Correct comment about btrfs install

[syslinux-bot for Gene Cumm]

Commit-ID:  7c8cd78e157997e3f1096b8afcb6defed61d2dff
Gitweb:     http://www.syslinux.org/commit/7c8cd78e157997e3f1096b8afcb6defed61d2dff
Author:     Gene Cumm <gene.cumm at gmail.com>
AuthorDate: Sun, 15 Nov 2015 09:14:21 -0500
Committer:  Gene Cumm <gene.cumm at gmail.com>
CommitDate: Sun, 15 Nov 2015 09:14:21 -0500

extlinux/main.c: Correct comment about btrfs install

As of commit ID 37eef640 (before 6.03-pre12, before 6.03), it is now in
Boot Area B.

Signed-off-by: Gene Cumm <gene.cumm at gmail.com>

---
 extlinux/main.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/extlinux/main.c b/extlinux/main.c
index 26eb43c..e2eb728 100644
--- a/extlinux/main.c
+++ b/extlinux/main.c
@@ -598,9 +598,12 @@ bail:
     return 1;
 }
 
-/* btrfs has to install ldlinux.sys in the first 64K blank area, which
-   is not managed by btrfs tree, so actually this is not installed as a file,
-   since the cow feature of btrfs would move the ldlinux.sys file everywhere. */
+/* btrfs has to install ldlinux.sys to a boot area, which is not managed by
+   btrfs tree, so actually this is not installed as a file, since the cow
+   feature of btrfs would move the ldlinux.sys file everywhere. Older
+   versions installed it to the first 64kiB (aka Boot Area A) but as of
+   commit ID 37eef640 (before 6.03-pre12, before 6.03), it is now in Boot
+   Area B (a 768kiB blank space at offset 256kiB). */
 int btrfs_install_file(const char *path, int devfd, struct stat *rst)
 {
     char *file;