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Commit f2693124 authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

fs_mgr: overlay: use alternate for backing storage 

When we have multiple physical super partitions, it is prudent to
take the alternate super physical partition in its raw entirety
rather than to construct a logical partition out of the current
super partition's limited remaining space.

SideEffect: alternate boot partitions destroyed for the sake of debug
Test: adb-remount-test.sh (including manually disabled to check
      both code paths).
Bug: 119885423
Change-Id: I368d3a5619f69de3b0d1fcad73c4b42d25d0d969
parent 13a66050

fs_mgr/README.overlayfs.md

+6 −0
Original line number Diff line number Diff line
@@ -95,6 +95,12 @@ Caveats 
  multiple reasons.

  NB: This is not a problem for fastbootd or recovery as overrides are

  disabled for those special boot scenarios.

- For implementation simplicity on retrofit dynamic partition devices,

  take the whole alternate super (eg: if "*a*" slot, then the whole of

  "*system_b*").

  Since landing a filesystem on the alternate super physical device

  without differentiating if it is setup to support logical or physical,

  the alternate slot metadata and previous content will be lost.

- If dynamic partitions runs out of space, resizing a logical

  partition larger may fail because of the scratch partition.

  If this happens, either fastboot flashall or adb enable-verity can

fs_mgr/fs_mgr_overlayfs.cpp

+18 −5
Original line number Diff line number Diff line
@@ -386,8 +386,10 @@ uint32_t fs_mgr_overlayfs_slot_number() { 
    return SlotNumberForSlotSuffix(fs_mgr_get_slot_suffix());

}



const auto kPhysicalDevice = "/dev/block/by-name/"s;



std::string fs_mgr_overlayfs_super_device(uint32_t slot_number) {

    return "/dev/block/by-name/" + fs_mgr_get_super_partition_name(slot_number);

    return kPhysicalDevice + fs_mgr_get_super_partition_name(slot_number);

}



bool fs_mgr_overlayfs_has_logical(const fstab* fstab) {
@@ -645,10 +647,16 @@ std::string fs_mgr_overlayfs_scratch_mount_type() { 
std::string fs_mgr_overlayfs_scratch_device() {

    if (!scratch_device_cache.empty()) return scratch_device_cache;



    // Is this a multiple super device (retrofit)?

    auto slot_number = fs_mgr_overlayfs_slot_number();

    auto super_device = fs_mgr_overlayfs_super_device(slot_number);

    auto path = fs_mgr_overlayfs_super_device(slot_number == 0);

    if (super_device == path) {

        // Create from within single super device;

        auto& dm = DeviceMapper::Instance();

        const auto partition_name = android::base::Basename(kScratchMountPoint);

    std::string path;

        if (!dm.GetDmDevicePathByName(partition_name, &path)) return "";

    }

    return scratch_device_cache = path;

}
@@ -679,6 +687,10 @@ bool fs_mgr_overlayfs_create_scratch(const fstab* fstab, std::string* scratch_de 
    *scratch_device = fs_mgr_overlayfs_scratch_device();

    *partition_exists = fs_mgr_rw_access(*scratch_device);

    auto partition_create = !*partition_exists;

    // Do we need to create a logical "scratch" partition?

    if (!partition_create && android::base::StartsWith(*scratch_device, kPhysicalDevice)) {

        return true;

    }

    auto slot_number = fs_mgr_overlayfs_slot_number();

    auto super_device = fs_mgr_overlayfs_super_device(slot_number);

    if (!fs_mgr_rw_access(super_device)) return false;
@@ -784,6 +796,7 @@ bool fs_mgr_overlayfs_setup_scratch(const fstab* fstab, bool* change) { 
bool fs_mgr_overlayfs_scratch_can_be_mounted(const std::string& scratch_device) {

    if (scratch_device.empty()) return false;

    if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) return false;

    if (android::base::StartsWith(scratch_device, kPhysicalDevice)) return true;

    if (fs_mgr_rw_access(scratch_device)) return true;

    auto slot_number = fs_mgr_overlayfs_slot_number();

    auto super_device = fs_mgr_overlayfs_super_device(slot_number);

fs_mgr/tests/adb-remount-test.sh

+31 −11
Original line number Diff line number Diff line
@@ -378,6 +378,11 @@ fi 
M=`adb_sh cat /proc/mounts | sed -n 's@\([^ ]*\) /mnt/scratch \([^ ]*\) .*@\2 on \1@p'`

[ -n "${M}" ] &&

  echo "${BLUE}[     INFO ]${NORMAL} scratch filesystem ${M}"

uses_dynamic_scratch=true

if [ "${M}" != "${M##*/dev/block/by-name/}" ]; then

  uses_dynamic_scratch=false

  scratch_partition="${M##*/dev/block/by-name/}"

fi

scratch_size=`adb_sh df -k /mnt/scratch </dev/null 2>/dev/null |

              while read device kblocks used available use mounted on; do

                if [ "/mnt/scratch" = "\${mounted}" ]; then
@@ -453,16 +458,30 @@ echo "${GREEN}[ RUN ]${NORMAL} flash vendor, confirm its content disappears 
  fastboot flash vendor ||

  ( fastboot reboot && false) ||

  die "fastboot flash vendor"

fastboot_getvar partition-type:${scratch_partition} raw ||

  ( fastboot reboot && false) ||

  die "fastboot can not see ${scratch_partition} parameters"

if ${uses_dynamic_scratch}; then

  # check ${scratch_partition} via fastboot

fastboot_getvar partition-type:${scratch_partition} raw &&

  fastboot_getvar has-slot:${scratch_partition} no &&

    fastboot_getvar is-logical:${scratch_partition} yes ||

    ( fastboot reboot && false) ||

    die "fastboot can not see ${scratch_partition} parameters"

else

  fastboot_getvar is-logical:${scratch_partition} no ||

    ( fastboot reboot && false) ||

    die "fastboot can not see ${scratch_partition} parameters"

fi

if ! ${uses_dynamic_scratch}; then

  fastboot reboot-bootloader ||

    die "Reboot into fastboot"

fi

if ${uses_dynamic_scratch}; then

  echo "${BLUE}[     INFO ]${NORMAL} expect fastboot erase ${scratch_partition} to fail" >&2

  fastboot erase ${scratch_partition} &&

    ( fastboot reboot || true) &&

    die "fastboot can erase ${scratch_partition}"

fi

echo "${BLUE}[     INFO ]${NORMAL} expect fastboot format ${scratch_partition} to fail" >&2

fastboot format ${scratch_partition} &&

  ( fastboot reboot || true) &&
@@ -507,12 +526,13 @@ check_eq "cat: /vendor/hello: No such file or directory" "${B}" after flash rm 


echo "${GREEN}[ RUN      ]${NORMAL} test fastboot flash to ${scratch_partition}" >&2



adb reboot-fastboot &&

adb reboot-fastboot ||

  die "Reboot into fastbootd"

dd if=/dev/zero of=/tmp/adb-remount-test.img bs=4096 count=16 2>/dev/null &&

  fastboot_wait 2m ||

  ( rm /tmp/adb-remount-test.img && false) ||

  die "reboot into fastboot"

fastboot flash ${scratch_partition} /tmp/adb-remount-test.img

fastboot flash --force ${scratch_partition} /tmp/adb-remount-test.img

err=${?}

rm /tmp/adb-remount-test.img

fastboot reboot ||