Merge pull request #10523 from poettering/fd-get-path-optimize

fd_get_path() optimization

src/basic/fd-util.c

@@ -353,22 +353,22 @@ bool fdname_is_valid(const char *s) {
 }
 
 int fd_get_path(int fd, char **ret) {
-        _cleanup_close_ int dir = -1;
+        char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
-        char fdname[DECIMAL_STR_MAX(int)];
         int r;
 
-        dir = open("/proc/self/fd/", O_CLOEXEC | O_DIRECTORY | O_PATH);
+        xsprintf(procfs_path, "/proc/self/fd/%i", fd);
-        if (dir < 0)
+        r = readlink_malloc(procfs_path, ret);
-                /* /proc is not available or not set up properly, we're most likely
+        if (r == -ENOENT) {
-                 * in some chroot environment. */
+                /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's make
+                 * things debuggable and distuingish the two. */
+
+                if (access("/proc/self/fd/", F_OK) < 0)
+                        /* /proc is not available or not set up properly, we're most likely in some chroot
+                         * environment. */
                         return errno == ENOENT ? -EOPNOTSUPP : -errno;
 
-        xsprintf(fdname, "%i", fd);
+                return -EBADF; /* The directory exists, hence it's the fd that doesn't. */
-
+        }
-        r = readlinkat_malloc(dir, fdname, ret);
-        if (r == -ENOENT)
-                /* If the file doesn't exist the fd is invalid */
-                return -EBADF;
 
         return r;
 }

src/basic/fs-util.c

@@ -132,7 +132,7 @@ int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char
 }
 
 int readlinkat_malloc(int fd, const char *p, char **ret) {
-        size_t l = 100;
+        size_t l = FILENAME_MAX+1;
         int r;
 
         assert(p);