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Commit 3ff87d89 authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

fs_mgr: add fs_mgr_has_shared_blocks and make default if overlayfs 

Add fs_mgr_has_shared_blocks in fs_mgr.  Use it as a default decision
to utilize overlayfs if not overridden by the platform.

Test: compile
Bug: 109821005
Change-Id: Ifab22a4c9898966515e268349c24bb4c28a39368
parent 53c96da7

fs_mgr/fs_mgr_overlayfs.cpp

+32 −3
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 


#include <dirent.h>

#include <errno.h>

#include <fcntl.h>

#include <linux/fs.h>

#include <selinux/selinux.h>

#include <stdio.h>
@@ -25,6 +26,7 @@ 
#include <sys/stat.h>

#include <sys/statvfs.h>

#include <sys/types.h>

#include <sys/vfs.h>

#include <unistd.h>



#include <map>
@@ -36,6 +38,8 @@ 
#include <android-base/macros.h>

#include <android-base/properties.h>

#include <android-base/strings.h>

#include <android-base/unique_fd.h>

#include <ext4_utils/ext4_utils.h>

#include <fs_mgr_overlayfs.h>

#include <fstab/fstab.h>
@@ -112,9 +116,11 @@ bool fs_mgr_filesystem_has_space(const char* mount_point) { 


bool fs_mgr_overlayfs_enabled(const struct fstab_rec* fsrec) {

    // readonly filesystem, can not be mount -o remount,rw

    // if squashfs or if free space is (near) zero making

    // such a remount virtually useless.

    return ("squashfs"s == fsrec->fs_type) || !fs_mgr_filesystem_has_space(fsrec->mount_point);

    // if squashfs or if free space is (near) zero making such a remount

    // virtually useless, or if there are shared blocks that prevent remount,rw

    return ("squashfs"s == fsrec->fs_type) ||

           fs_mgr_has_shared_blocks(fsrec->mount_point, fsrec->blk_device) ||

           !fs_mgr_filesystem_has_space(fsrec->mount_point);

}



constexpr char upper_name[] = "upper";
@@ -191,6 +197,7 @@ bool fs_mgr_wants_overlayfs(const fstab_rec* fsrec) { 


    auto fsrec_mount_point = fsrec->mount_point;

    if (!fsrec_mount_point) return false;

    if (!fsrec->blk_device) return false;



    if (!fsrec->fs_type) return false;
@@ -493,3 +500,25 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) { 
}



#endif  // ALLOW_ADBD_DISABLE_VERITY != 0



bool fs_mgr_has_shared_blocks(const std::string& mount_point, const std::string& dev) {

    struct statfs fs;

    if ((statfs((mount_point + "/lost+found").c_str(), &fs) == -1) ||

        (fs.f_type != EXT4_SUPER_MAGIC)) {

        return false;

    }



    android::base::unique_fd fd(open(dev.c_str(), O_RDONLY | O_CLOEXEC));

    if (fd < 0) return false;



    struct ext4_super_block sb;

    if ((TEMP_FAILURE_RETRY(lseek64(fd, 1024, SEEK_SET)) < 0) ||

        (TEMP_FAILURE_RETRY(read(fd, &sb, sizeof(sb))) < 0)) {

        return false;

    }



    struct fs_info info;

    if (ext4_parse_sb(&sb, &info) < 0) return false;



    return (info.feat_ro_compat & EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS) != 0;

}

fs_mgr/include/fs_mgr_overlayfs.h

+3 −0
Original line number Diff line number Diff line
@@ -18,7 +18,10 @@ 


#include <fstab/fstab.h>



#include <string>



bool fs_mgr_overlayfs_mount_all();

bool fs_mgr_overlayfs_setup(const char* backing = nullptr, const char* mount_point = nullptr,

                            bool* change = nullptr);

bool fs_mgr_overlayfs_teardown(const char* mount_point = nullptr, bool* change = nullptr);

bool fs_mgr_has_shared_blocks(const std::string& mount_point, const std::string& dev);