[PATCH v2 7/9] btrfs: add environment block to reserved header area

[Michael Chang via Grub-devel <grub-devel@gnu.org>]

This patch reserves space for the GRUB environment block inside the
Btrfs header. The block is placed at an offset of 256 KiB from the start
of the device and occupies one sector. To protect the space, overflow
guard sectors are placed before and after the reserved block.

The Btrfs header already defines regions for bootloader use. By adding
this entry, GRUB gains a fixed and safe location to store the
environment block without conflicting with other structures in the
header.

Signed-off-by: Michael Chang <mchang@suse.com>
---
 grub-core/fs/btrfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 7bf8d922f..d35ff5fa5 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -2341,7 +2341,7 @@ struct embed_region {
 
 static const struct {
   struct embed_region available;
-  struct embed_region used[6];
+  struct embed_region used[7];
 } btrfs_head = {
   .available = {0, GRUB_DISK_KiB_TO_SECTORS (1024)}, /* The first 1 MiB. */
   .used = {
@@ -2349,6 +2349,7 @@ static const struct {
     {GRUB_DISK_KiB_TO_SECTORS (64) - 1, 1},                        /* Overflow guard. */
     {GRUB_DISK_KiB_TO_SECTORS (64), GRUB_DISK_KiB_TO_SECTORS (4)}, /* 4 KiB superblock. */
     {GRUB_DISK_KiB_TO_SECTORS (68), 1},                            /* Overflow guard. */
+    {(ENV_BTRFS_OFFSET >> GRUB_DISK_SECTOR_BITS) - 1, 3},          /* Environment Block. */
     {GRUB_DISK_KiB_TO_SECTORS (1024) - 1, 1},                      /* Overflow guard. */
     {0, 0}                                                         /* Array terminator. */
   }
-- 
2.51.0


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