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/** |
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* This file is part of the CernVM File System |
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*/ |
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#include "sync_union_overlayfs.h" |
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#include <sys/types.h> |
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#include <cassert> |
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#include <climits> |
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#include <string> |
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#include <vector> |
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#include "sync_item.h" |
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#include "sync_mediator.h" |
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#include "sync_union.h" |
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#include "util/capabilities.h" |
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#include "util/exception.h" |
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#include "util/fs_traversal.h" |
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#include "util/logging.h" |
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#include "util/shared_ptr.h" |
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namespace publish { |
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SyncUnionOverlayfs::SyncUnionOverlayfs(SyncMediator *mediator, |
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const string &rdonly_path, |
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const string &union_path, |
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const string &scratch_path) |
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: SyncUnion(mediator, rdonly_path, union_path, scratch_path) |
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, hardlink_lower_inode_(0) { } |
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bool SyncUnionOverlayfs::Initialize() { |
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// trying to obtain CAP_SYS_ADMIN to read 'trusted' xattrs in the scratch |
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// directory of an OverlayFS installation |
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return ObtainSysAdminCapability() && SyncUnion::Initialize(); |
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} |
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void SyncUnionOverlayfs::PreprocessSyncItem(SharedPtr<SyncItem> entry) const { |
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SyncUnion::PreprocessSyncItem(entry); |
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if (entry->IsGraftMarker() || entry->IsWhiteout() || entry->IsDirectory()) { |
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return; |
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} |
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CheckForBrokenHardlink(entry); |
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MaskFileHardlinks(entry); |
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} |
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void SyncUnionOverlayfs::CheckForBrokenHardlink( |
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SharedPtr<SyncItem> entry) const { |
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if (!entry->IsNew() && !entry->WasDirectory() |
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&& entry->GetRdOnlyLinkcount() > 1) { |
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PANIC(kLogStderr, |
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"OverlayFS has copied-up a file (%s) " |
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"with existing hardlinks in lowerdir " |
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"(linkcount %d). OverlayFS cannot handle " |
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"hardlinks and would produce " |
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"inconsistencies. \n\n" |
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"Consider running this command: \n" |
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" cvmfs_server eliminate-hardlinks\n\n" |
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"Aborting...", |
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entry->GetUnionPath().c_str(), entry->GetRdOnlyLinkcount()); |
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} |
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} |
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void SyncUnionOverlayfs::MaskFileHardlinks(SharedPtr<SyncItem> entry) const { |
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assert(entry->IsRegularFile() || entry->IsSymlink() |
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|| entry->IsSpecialFile()); |
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if (entry->GetUnionLinkcount() > 1) { |
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LogCvmfs(kLogPublish, kLogStderr, |
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"Warning: Found file with linkcount > 1 " |
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"(%s). We will break up these hardlinks.", |
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entry->GetUnionPath().c_str()); |
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entry->MaskHardlink(); |
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} |
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} |
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void SyncUnionOverlayfs::Traverse() { |
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assert(this->IsInitialized()); |
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FileSystemTraversal<SyncUnionOverlayfs> traversal(this, scratch_path(), true); |
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traversal.fn_enter_dir = &SyncUnionOverlayfs::EnterDirectory; |
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traversal.fn_leave_dir = &SyncUnionOverlayfs::LeaveDirectory; |
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traversal.fn_new_file = &SyncUnionOverlayfs::ProcessRegularFile; |
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traversal.fn_new_character_dev = &SyncUnionOverlayfs::ProcessCharacterDevice; |
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traversal.fn_new_block_dev = &SyncUnionOverlayfs::ProcessBlockDevice; |
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traversal.fn_new_fifo = &SyncUnionOverlayfs::ProcessFifo; |
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traversal.fn_new_socket = &SyncUnionOverlayfs::ProcessSocket; |
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traversal.fn_ignore_file = &SyncUnionOverlayfs::IgnoreFilePredicate; |
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traversal.fn_new_dir_prefix = &SyncUnionOverlayfs::ProcessDirectory; |
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traversal.fn_new_symlink = &SyncUnionOverlayfs::ProcessSymlink; |
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LogCvmfs(kLogUnionFs, kLogVerboseMsg, |
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"OverlayFS starting traversal " |
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"recursion for scratch_path=[%s]", |
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scratch_path().c_str()); |
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traversal.Recurse(scratch_path()); |
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} |
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/** |
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* Wrapper around readlink to read the value of the symbolic link |
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* and return true if it is equal to the supplied value, or false |
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* otherwise (including if any errors occur) |
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* |
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* @param[in] path to the symbolic link |
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* @param[in] value to compare to link value |
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*/ |
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bool SyncUnionOverlayfs::ReadlinkEquals(string const &path, |
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string const &compare_value) { |
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char *buf; |
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size_t compare_len; |
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// A readlink target can never exceed PATH_MAX; bounding the length here also |
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// lets the compiler prove the size passed to readlink() is sane (otherwise |
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// the value range derived from std::string::length() triggers a spurious |
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// -Wstringop-overflow warning from the fortified readlink wrapper). |
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if (compare_value.length() >= PATH_MAX) { |
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return false; |
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} |
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// Compare to one more than compare_value length in case the link value |
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// begins with compare_value but ends with something else |
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compare_len = compare_value.length() + 1; |
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// Allocate enough space for compare_len and terminating null |
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buf = static_cast<char *>(alloca(compare_len + 1)); |
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const ssize_t len = ::readlink(path.c_str(), buf, compare_len); |
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if (len != -1) { |
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buf[len] = '\0'; |
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// have link, return true if it is equal to compare_value |
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return (std::string(buf) == compare_value); |
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} else { |
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// Error, return false |
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LogCvmfs(kLogUnionFs, kLogDebug, |
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"SyncUnionOverlayfs::ReadlinkEquals error reading link [%s]: %d\n", |
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path.c_str(), errno); |
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return false; |
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} |
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} |
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/** |
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* Checks if a given file path has a specified extended attribute attached. |
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* |
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* @param[in] path to the file to be checked |
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* @param[in] attr_name fully qualified name of the extend attribute |
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* (i.e. trusted.overlay.opaque) |
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* @return true if attribute is found |
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*/ |
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bool SyncUnionOverlayfs::HasXattr(string const &path, string const &attr_name) { |
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// TODO(reneme): it is quite heavy-weight to allocate an object that contains |
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// an std::map<> just to check if an xattr is there... |
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const UniquePtr<XattrList> xattrs(XattrList::CreateFromFile(path)); |
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assert(xattrs.IsValid()); |
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std::vector<std::string> attrs = xattrs->ListKeys(); |
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std::vector<std::string>::const_iterator i = attrs.begin(); |
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const std::vector<std::string>::const_iterator iend = attrs.end(); |
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LogCvmfs(kLogCvmfs, kLogDebug, "Attrs:"); |
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for (; i != iend; ++i) { |
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LogCvmfs(kLogCvmfs, kLogDebug, "Attr: %s", i->c_str()); |
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} |
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return xattrs.IsValid() && xattrs->Has(attr_name); |
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} |
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bool SyncUnionOverlayfs::IsWhiteoutEntry(SharedPtr<SyncItem> entry) const { |
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/** |
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* There seem to be two versions of overlayfs out there and in production: |
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* 1. whiteouts are 'character device' files |
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* 2. whiteouts are symlinks pointing to '(overlay-whiteout)' |
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* 3. whiteouts are marked as .wh. (as in aufs) |
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*/ |
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const bool is_chardev_whiteout = entry->IsCharacterDevice() |
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&& entry->GetRdevMajor() == 0 |
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&& entry->GetRdevMinor() == 0; |
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if (is_chardev_whiteout) |
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return true; |
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const std::string whiteout_prefix_ = ".wh."; |
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const bool has_wh_prefix = HasPrefix(entry->filename().c_str(), |
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whiteout_prefix_, true); |
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if (has_wh_prefix) |
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return true; |
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const bool is_symlink_whiteout = entry->IsSymlink() |
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&& IsWhiteoutSymlinkPath( |
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entry->GetScratchPath()); |
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if (is_symlink_whiteout) |
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return true; |
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return false; |
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} |
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bool SyncUnionOverlayfs::IsWhiteoutSymlinkPath(const string &path) const { |
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const bool is_whiteout = ReadlinkEquals(path, "(overlay-whiteout)"); |
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// TODO(reneme): check for the xattr trusted.overlay.whiteout |
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// Note: This requires CAP_SYS_ADMIN or root... >.< |
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if (is_whiteout) { |
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LogCvmfs(kLogUnionFs, kLogDebug, "OverlayFS [%s] is whiteout symlink", |
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path.c_str()); |
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} else { |
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LogCvmfs(kLogUnionFs, kLogDebug, "OverlayFS [%s] is not a whiteout symlink", |
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path.c_str()); |
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} |
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return is_whiteout; |
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} |
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bool SyncUnionOverlayfs::IsOpaqueDirectory( |
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SharedPtr<SyncItem> directory) const { |
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const std::string path = directory->GetScratchPath(); |
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return DirectoryExists(path) && IsOpaqueDirPath(path); |
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} |
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bool SyncUnionOverlayfs::IsOpaqueDirPath(const string &path) const { |
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const bool is_opaque = HasXattr(path.c_str(), "trusted.overlay.opaque"); |
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if (is_opaque) { |
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LogCvmfs(kLogUnionFs, kLogDebug, "OverlayFS [%s] has opaque xattr", |
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path.c_str()); |
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} |
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return is_opaque; |
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} |
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string SyncUnionOverlayfs::UnwindWhiteoutFilename( |
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SharedPtr<SyncItem> entry) const { |
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const std::string whiteout_prefix_ = ".wh."; |
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if (HasPrefix(entry->filename().c_str(), whiteout_prefix_, true)) { |
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return entry->filename().substr(whiteout_prefix_.length()); |
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} else { |
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return entry->filename(); |
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} |
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} |
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} // namespace publish |
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