this repo has no description
Improve DPREFIX performance on NFS mounts
+93
-70
+93
-70
src/libdyld/VirtualPrefix.cpp
+93
-70
src/libdyld/VirtualPrefix.cpp
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#include <list>
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#include <cassert>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <iostream>
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#include <cstdio>
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#include <dirent.h>
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path += '/';
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real_path.replace(g_prefix.size(), std::string::npos, path);
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if (!had_failure) // check if there is any sense in using opendir again
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if (!had_failure) // check if there is any sense in using opendir() or lstat() again
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{
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DIR* dir;
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struct dirent* ent;
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struct stat st;
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bool isLink = false;
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bool is_system_root;
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// std::cout << "*** opendir: " << real_path << std::endl;
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dir = opendir(real_path.c_str());
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if (dir != nullptr)
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real_path.replace(g_prefix.size(), std::string::npos, path);
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real_path += comp;
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// Do NOT perform symlink resolution on /system-root,
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// because that should look like a bind mount rather than
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// a symlink from inside the DPREFIX
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is_system_root = (it == path_components.begin())
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&& (comp == (SYSTEM_ROOT+1));
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// We try an lstat() first as an optimization,
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// because the opendir() path below is VERY slow on NFS mounts.
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if (lstat(real_path.c_str(), &st) == 0)
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{
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isLink = S_ISLNK(st.st_mode);
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}
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else
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{
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std::string best_match;
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unsigned char best_match_type;
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// std::cout << "*** opendir: " << real_path << std::endl;
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real_path.resize(real_path.length() - comp.length());
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while ((ent = readdir(dir)) != nullptr)
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dir = opendir(real_path.c_str());
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if (dir != nullptr)
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{
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if (comp == ent->d_name)
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break;
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else if (strcasecmp(comp.c_str(), ent->d_name) == 0)
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std::string best_match;
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unsigned char best_match_type;
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while ((ent = readdir(dir)) != nullptr)
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{
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best_match = ent->d_name;
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best_match_type = ent->d_type;
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// Commented out: replaced with lstat() above
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/* if (comp == ent->d_name)
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break;
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else*/ if (strcasecmp(comp.c_str(), ent->d_name) == 0)
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{
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best_match = ent->d_name;
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best_match_type = ent->d_type;
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}
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}
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}
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if (ent != nullptr || !best_match.empty())
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{
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bool is_system_root;
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if (ent == nullptr)
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{
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// correct the case
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comp = best_match;
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}
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else
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best_match_type = ent->d_type;
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// Perform symlink resolution
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//
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// Do NOT perform symlink resolution on /system-root,
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// because that should look like a bind mount rather than
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// a symlink from inside the DPREFIX
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is_system_root = (it == path_components.begin())
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&& (comp == (SYSTEM_ROOT+1));
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if (best_match_type == DT_LNK && !is_system_root)
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if (ent != nullptr || !best_match.empty())
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{
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char link[256];
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int len;
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real_path += comp;
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// std::cout << "*** readlink: " << real_path << std::endl;
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len = readlink(real_path.c_str(), link, sizeof(link)-1);
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if (len > 0)
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if (ent == nullptr)
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{
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// correct the case
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comp = best_match;
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}
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else
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best_match_type = ent->d_type;
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if (best_match_type == DT_LNK && !is_system_root)
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{
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std::list<std::string> link_components;
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link[len] = '\0';
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link_components = explode_path(link);
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if (link[0] == '/')
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{
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it++;
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it = path_components.erase(path_components.begin(), it);
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}
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else
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{
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it = path_components.erase(it);
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}
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path_components.insert(it,
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link_components.begin(),
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link_components.end());
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closedir(dir);
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goto restart_process;
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isLink = true;
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real_path += comp;
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}
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}
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else
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had_failure = true;
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closedir(dir);
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}
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else
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had_failure = true;
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}
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// Perform symlink resolution
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if (isLink && !is_system_root)
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{
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char link[256];
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int len;
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closedir(dir);
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// std::cout << "*** readlink: " << real_path << std::endl;
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len = readlink(real_path.c_str(), link, sizeof(link)-1);
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if (len > 0)
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{
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std::list<std::string> link_components;
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link[len] = '\0';
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link_components = explode_path(link);
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if (link[0] == '/')
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{
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// absolute symlink
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it++;
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it = path_components.erase(path_components.begin(), it);
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}
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else
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{
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// relative symlink
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it = path_components.erase(it);
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}
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path_components.insert(it,
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link_components.begin(),
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link_components.end());
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// We always restart the process
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// 1) For absolute symlinks, because we're moving to a completely different path
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// 2) For relative symlinks, because they may contain '..'
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goto restart_process;
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}
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}
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else
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had_failure = true;
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}
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path += comp;