From fd2f0b4dc496319f94d024b0c841b639245df0a4 Mon Sep 17 00:00:00 2001
From: Daniel Rosenberg <drosen@google.com>
Date: Thu, 27 Aug 2015 13:42:20 -0700
Subject: [PATCH] fs_mgr: Add support for A/B partitions

Allow partitions to be marked as A/B partitions
using the slotselect flag in fstab. The partitions
can be identified by appending the correct suffix
to the block device listed in the fstab. The suffix
is provided by the bootloader through a command line
parameter or the device tree, and can be found in
ro.boot.slot_suffix or read from the boot_control HAL.

Change-Id: I6846d80e857f95bfb8f282f4ab81167394613bbe
Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs_mgr/fs_mgr_fstab.c | 25 +++++++++++++++++++++++++
 fs_mgr/fs_mgr_priv.h  |  1 +
 2 files changed, 26 insertions(+)

diff --git a/fs_mgr/fs_mgr_fstab.c b/fs_mgr/fs_mgr_fstab.c
index f24af1f1d..a44d03458 100644
--- a/fs_mgr/fs_mgr_fstab.c
+++ b/fs_mgr/fs_mgr_fstab.c
@@ -22,6 +22,8 @@
 #include <sys/mount.h>
 #include <unistd.h>
 
+#include <cutils/properties.h>
+
 #include "fs_mgr_priv.h"
 
 struct fs_mgr_flag_values {
@@ -74,6 +76,7 @@ static struct flag_list fs_mgr_flags[] = {
     { "noemulatedsd", MF_NOEMULATEDSD },
     { "notrim",       MF_NOTRIM },
     { "formattable", MF_FORMATTABLE },
+    { "slotselect",  MF_SLOTSELECT },
     { "defaults",    0 },
     { 0,             0 },
 };
@@ -329,6 +332,23 @@ struct fstab *fs_mgr_read_fstab(const char *fstab_path)
         fstab->recs[cnt].partnum = flag_vals.partnum;
         fstab->recs[cnt].swap_prio = flag_vals.swap_prio;
         fstab->recs[cnt].zram_size = flag_vals.zram_size;
+
+        /* If an A/B partition, modify block device to be the real block device */
+        if (fstab->recs[cnt].fs_mgr_flags & MF_SLOTSELECT) {
+            char propbuf[PROPERTY_VALUE_MAX];
+            char *tmp;
+
+            /* use the kernel parameter if set */
+            property_get("ro.boot.slot_suffix", propbuf, "");
+
+            if (asprintf(&tmp, "%s%s", fstab->recs[cnt].blk_device, propbuf) > 0) {
+                free(fstab->recs[cnt].blk_device);
+                fstab->recs[cnt].blk_device = tmp;
+            } else {
+                ERROR("Error updating block device name\n");
+                goto err;
+            }
+        }
         cnt++;
     }
     fclose(fstab_file);
@@ -480,3 +500,8 @@ int fs_mgr_is_formattable(struct fstab_rec *fstab)
 {
     return fstab->fs_mgr_flags & (MF_FORMATTABLE);
 }
+
+int fs_mgr_is_slotselect(struct fstab_rec *fstab)
+{
+    return fstab->fs_mgr_flags & MF_SLOTSELECT;
+}
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 682fd1101..a87092efc 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -79,6 +79,7 @@
 #define MF_NOTRIM       0x1000
 #define MF_FILEENCRYPTION 0x2000
 #define MF_FORMATTABLE  0x4000
+#define MF_SLOTSELECT   0x8000
 
 #define DM_BUF_SIZE 4096