From b864dc9ef4aa00191dfa81accbe93f9ed0382261 Mon Sep 17 00:00:00 2001

From: Michal Sekletar <msekleta@redhat.com>

Date: Tue, 9 Mar 2021 17:22:32 +0100

Subject: [PATCH] install: refactor find_symlinks() and don't search for

 symlinks recursively

After all we are only interested in symlinks either in top-level config

directory or in .wants and .requires sub-directories.

As a bonus this should speed up ListUnitFiles() roughly 3-4x on systems

with a lot of units that use drop-ins (e.g. SSH jump hosts with a lot of

user session scopes).

(cherry picked from commit 43b4e3058c106e663bbd5413e7bd106e55d6fd79)

Resolves: #1828758

---

 src/shared/install.c | 207 ++++++++++++++++++++-----------------------

 1 file changed, 96 insertions(+), 111 deletions(-)

diff --git a/src/shared/install.c b/src/shared/install.c

index f2f968e329..761bf8074e 100644

--- a/src/shared/install.c

+++ b/src/shared/install.c

@@ -503,137 +503,88 @@ static int remove_marked_symlinks(

         return r;

 }

-static int find_symlinks_fd(

+static int find_symlinks_in_directory(

+                DIR *dir,

+                const char *dir_path,

                 const char *root_dir,

                 const char *name,

-                int fd,

-                const char *path,

                 const char *config_path,

                 bool *same_name_link) {

+        struct dirent *de;

         int r = 0;

-        _cleanup_closedir_ DIR *d = NULL;

-        assert(name);

-        assert(fd >= 0);

-        assert(path);

-        assert(config_path);

-        assert(same_name_link);

-

-        d = fdopendir(fd);

-        if (!d) {

-                safe_close(fd);

-                return -errno;

-        }

-

-        for (;;) {

-                struct dirent *de;

-

-                errno = 0;

-                de = readdir(d);

-                if (!de && errno != 0)

-                        return -errno;

+        FOREACH_DIRENT(de, dir, return -errno) {

+                _cleanup_free_ char *p = NULL, *dest = NULL;

+                bool found_path = false, found_dest, b = false;

+                int q;

-                if (!de)

-                        return r;

+                dirent_ensure_type(dir, de);

-                if (hidden_file(de->d_name))

+                if (de->d_type != DT_LNK)

                         continue;

-                dirent_ensure_type(d, de);

-

-                if (de->d_type == DT_DIR) {

-                        int nfd, q;

-                        _cleanup_free_ char *p = NULL;

-

-                        nfd = openat(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);

-                        if (nfd < 0) {

-                                if (errno == ENOENT)

-                                        continue;

-

-                                if (r == 0)

-                                        r = -errno;

-                                continue;

-                        }

-

-                        p = path_make_absolute(de->d_name, path);

-                        if (!p) {

-                                safe_close(nfd);

-                                return -ENOMEM;

-                        }

+                /* Acquire symlink name */

+                p = path_make_absolute(de->d_name, dir_path);

+                if (!p)

+                        return -ENOMEM;

-                        /* This will close nfd, regardless whether it succeeds or not */

-                        q = find_symlinks_fd(root_dir, name, nfd, p, config_path, same_name_link);

-                        if (q > 0)

-                                return 1;

+                /* Acquire symlink destination */

+                q = readlinkat_malloc(dirfd(dir), de->d_name, &dest);

+                if (q == -ENOENT)

+                        continue;

+                if (q < 0) {

                         if (r == 0)

                                 r = q;

+                        continue;

+                }

-                } else if (de->d_type == DT_LNK) {

-                        _cleanup_free_ char *p = NULL, *dest = NULL;

-                        bool found_path, found_dest, b = false;

-                        int q;

+                /* Make absolute */

+                if (!path_is_absolute(dest)) {

+                        char *x;

-                        /* Acquire symlink name */

-                        p = path_make_absolute(de->d_name, path);

-                        if (!p)

+                        x = path_join(dir_path, dest, NULL);

+                        if (!x)

                                 return -ENOMEM;

-                        /* Acquire symlink destination */

-                        q = readlink_malloc(p, &dest);

-                        if (q < 0) {

-                                if (q == -ENOENT)

-                                        continue;

+                        free(dest);

+                        dest = x;

-                                if (r == 0)

-                                        r = q;

-                                continue;

-                        }

-

-                        /* Make absolute */

-                        if (!path_is_absolute(dest)) {

-                                char *x;

-

-                                x = prefix_root(root_dir, dest);

-                                if (!x)

-                                        return -ENOMEM;

-

-                                free(dest);

-                                dest = x;

-                        }

+                }

-                        /* Check if the symlink itself matches what we

-                         * are looking for */

-                        if (path_is_absolute(name))

-                                found_path = path_equal(p, name);

-                        else

-                                found_path = streq(de->d_name, name);

+                /* Check if the symlink itself matches what we

+                        * are looking for */

+                if (path_is_absolute(name))

+                        found_path = path_equal(p, name);

+                else

+                        found_path = streq(de->d_name, name);

-                        /* Check if what the symlink points to

-                         * matches what we are looking for */

-                        if (path_is_absolute(name))

-                                found_dest = path_equal(dest, name);

-                        else

-                                found_dest = streq(basename(dest), name);

+                /* Check if what the symlink points to

+                        * matches what we are looking for */

+                if (path_is_absolute(name))

+                        found_dest = path_equal(dest, name);

+                else

+                        found_dest = streq(basename(dest), name);

-                        if (found_path && found_dest) {

-                                _cleanup_free_ char *t = NULL;

+                if (found_path && found_dest) {

+                        _cleanup_free_ char *t = NULL;

-                                /* Filter out same name links in the main

-                                 * config path */

-                                t = path_make_absolute(name, config_path);

-                                if (!t)

-                                        return -ENOMEM;

-

-                                b = path_equal(t, p);

-                        }

+                        /* Filter out same name links in the main

+                                * config path */

+                        t = path_make_absolute(name, config_path);

+                        if (!t)

+                                return -ENOMEM;

-                        if (b)

-                                *same_name_link = true;

-                        else if (found_path || found_dest)

-                                return 1;

+                        b = path_equal(p, t);

                 }

+

+                if (b)

+                        *same_name_link = true;

+                else if (found_path || found_dest)

+                        return 1;

         }

+

+        return r;

 }

 static int find_symlinks(

@@ -642,21 +593,55 @@ static int find_symlinks(

                 const char *config_path,

                 bool *same_name_link) {

-        int fd;

+        _cleanup_closedir_ DIR *config_dir = NULL;

+        struct dirent *de;

+        int r = 0;

         assert(name);

         assert(config_path);

         assert(same_name_link);

-        fd = open(config_path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);

-        if (fd < 0) {

-                if (errno == ENOENT)

+        config_dir = opendir(config_path);

+        if (!config_dir) {

+                if (IN_SET(errno, ENOENT, ENOTDIR, EACCES))

                         return 0;

                 return -errno;

         }

-        /* This takes possession of fd and closes it */

-        return find_symlinks_fd(root_dir, name, fd, config_path, config_path, same_name_link);

+        FOREACH_DIRENT(de, config_dir, return -errno) {

+                const char *suffix;

+                _cleanup_free_ const char *path = NULL;

+                _cleanup_closedir_ DIR *d = NULL;

+

+                dirent_ensure_type(config_dir, de);

+

+                if (de->d_type != DT_DIR)

+                        continue;

+

+                suffix = strrchr(de->d_name, '.');

+                if (!streq(suffix, ".wants") && !streq(suffix, ".requires"))

+                        continue;

+

+                path = path_join(config_path, de->d_name, NULL);

+                if (!path)

+                        return -ENOMEM;

+

+                d = opendir(path);

+                if (!d) {

+                        log_error_errno(errno, "Failed to open directory '%s' while scanning for symlinks, ignoring: %m", path);

+                        continue;

+                }

+

+                r = find_symlinks_in_directory(d, path, root_dir, name, config_path, same_name_link);

+                if (r > 0)

+                        return 1;

+                else if (r < 0)

+                        log_debug_errno(r, "Failed to lookup for symlinks in '%s': %m", path);

+        }

+

+        /* We didn't find any suitable symlinks in .wants or .requires directories, let's look for linked unit files in this directory. */

+        rewinddir(config_dir);

+        return find_symlinks_in_directory(config_dir, config_path, root_dir, name, config_path, same_name_link);

 }

 static int find_symlinks_in_scope(