[PATCH 4/6] partitions: gpt: write inactive GPT first

[Sascha Hauer <s.hauer@pengutronix.de>]

There are two GPT partition tables on a device, the primary at the
beginning of a device and the alternate at the end of the device.

For the sake of being more robust against power failures let's write the
inactive GPT first and the currently active one afterwards. This always
leaves us a usable GPT on the device when updating the partition table.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 common/partitions/efi.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/common/partitions/efi.c b/common/partitions/efi.c
index 8da62acf36646b62ff2fac25673adbc48650d299..1766f0123353d502065673d02e983e6cdd51b9af 100644
--- a/common/partitions/efi.c
+++ b/common/partitions/efi.c
@@ -27,6 +27,8 @@ struct efi_partition_desc {
 	gpt_header *gpt;
 	gpt_entry *ptes;
 	struct param_d *param_guid;
+	bool good_pgpt;
+	bool good_agpt;
 };
 
 struct efi_partition {
@@ -424,6 +426,9 @@ static int find_valid_gpt(struct efi_partition_desc *epd, void *buf)
 	if (IS_ENABLED(CONFIG_PARTITION_DISK_EFI_GPT_COMPARE))
 		compare_gpts(blk->dev, pgpt, agpt, lastlba);
 
+	epd->good_pgpt = good_pgpt;
+	epd->good_agpt = good_agpt;
+
 	/* The good cases */
 	if (good_pgpt) {
 		epd->gpt  = pgpt;
@@ -810,11 +815,11 @@ static __maybe_unused int efi_partition_write(struct partition_desc *pd)
 	if (ret)
 		return ret;
 
-	ret = __efi_partition_write(epd, true);
+	ret = __efi_partition_write(epd, !epd->good_pgpt);
 	if (ret)
 		goto err_block_write;
 
-	ret = __efi_partition_write(epd, false);
+	ret = __efi_partition_write(epd, epd->good_pgpt);
 	if (ret)
 		goto err_block_write;
 

-- 
2.47.3