s3:smbd: let openat_pathref_dirfsp_nosymlink() try VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS...

This will reduce the amount of syscalls and the related cost drastically
for long path names.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>

diff --git a/source3/smbd/files.c b/source3/smbd/files.c
index 23de0ad63c2287e6f23eb85d710a24ca459674aa..af135d6e95a54774e93168ea52dadd84f4262213 100644 (file)
--- a/source3/smbd/files.c
+++ b/source3/smbd/files.c
@@ -820,6 +820,69 @@ NTSTATUS openat_pathref_dirfsp_nosymlink(
                rel_fname.base_name = next;
        }
 
+       if (conn->open_how_resolve & VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS) {
+
+               /*
+                * Try a direct openat2 with RESOLVE_NO_SYMLINKS to
+                * avoid the openat/close loop further down.
+                */
+
+               rel_fname.base_name = discard_const_p(char, path_in);
+               how.resolve = VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS;
+
+               fd = SMB_VFS_OPENAT(conn, dirfsp, &rel_fname, fsp, &how);
+               if (fd >= 0) {
+                       fsp_set_fd(fsp, fd);
+                       TALLOC_FREE(full_fname.base_name);
+                       full_fname = rel_fname;
+                       goto done;
+               }
+
+               status = map_nt_error_from_unix(errno);
+               DBG_DEBUG("SMB_VFS_OPENAT(%s, %s, RESOLVE_NO_SYMLINKS) returned %d %s => %s\n",
+                         smb_fname_str_dbg(dirfsp->fsp_name), path_in,
+                         errno, strerror(errno), nt_errstr(status));
+               SMB_ASSERT(fd == -1);
+               switch (errno) {
+               case ENOSYS:
+                       /*
+                        * We got ENOSYS, so fallback to the old code
+                        * if the kernel doesn't support openat2() yet.
+                        */
+                       break;
+
+               case ELOOP:
+               case ENOTDIR:
+                       /*
+                        * For ELOOP we also fallback in order to
+                        * return the correct information with
+                        * NT_STATUS_STOPPED_ON_SYMLINK.
+                        *
+                        * O_NOFOLLOW|O_DIRECTORY results in
+                        * ENOTDIR instead of ELOOP for the final
+                        * component.
+                        */
+                       break;
+
+               case ENOENT:
+                       /*
+                        * If we got ENOENT, the filesystem could
+                        * be case sensitive. For now we only do
+                        * the get_real_filename_at() dance in
+                        * the fallback loop below.
+                        */
+                       break;
+
+               default:
+                       goto fail;
+               }
+
+               /*
+                * Just fallback to the openat loop
+                */
+               how.resolve = 0;
+       }
+
        /*
         * Now we loop over all components
         * opening each one and using it
@@ -967,6 +1030,7 @@ next:
                dirfsp = NULL;
        }
 
+done:
        fsp->fsp_flags.is_pathref = true;
        fsp->fsp_name = NULL;