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fs_mgr: add fs_mgr_has_shared_blocks and make default if overlayfs

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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
This commit is contained in:
Mark Salyzyn 2018-07-02 10:45:25 -07:00
parent 53c96da749
commit 3ff87d89ef
2 changed files with 35 additions and 3 deletions
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35
fs_mgr/fs_mgr_overlayfs.cpp
View file

@ -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;
}

3
fs_mgr/include/fs_mgr_overlayfs.h
View file

@ -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);