The du circular warning can still be hit even though a file system is in good condition. All we need to do is to get the message is to begin traversing the file system between the bind mount source and bind mount target directories, i.e this short script reproduces the problem:
# mkdir -p a/b/c # mount -o bind a a/b/c # du a/b The problem is that in this case, the first directory that is detected by fts as a duplicate directory is directory a/b/c/b which is not a mount point. The solution is to traverse the structure all the way to a/b (excluding a/b) which is detected as the base of the cycle and look up all these directories in the mount table. I'm attaching the patch that fixed this problem for me. -Boris
>From 2359875e69d7dedfe505c45beea9277561368b45 Mon Sep 17 00:00:00 2001 From: Boris Ranto <[email protected]> Date: Mon, 1 Dec 2014 09:24:14 +0100 Subject: [PATCH] du: handle sub-bind-mount cycles gracefully This patch fixes the handling of sub-bind-mount cycles which are incorrectly detected as the filesystem errors. If you bind mount the directory 'a' to its subdirectory 'a/b/c' and then run 'du a/b' you will get the circular dependency warning even though nothing is wrong with the file system. This happens because the first directory that is traversed twice in this case is not a bind mount but a child of bind mount. The solution is to traverse all the directories in the cycle that fts detected and check whether they are not a (bind) mount. * src/du.c (mount_point_in_fts_cycle): New function that checks whether any of the directories in the cycle that fts detected is a mount point. * src/du.c (process_file): Update the function to use the new function that looks up all the directories in the fts cycle instead of only the last one. * tests/du/bind-mount-dir-cycle-v2.sh: New test case that exhibits the described behaviour. --- src/du.c | 21 +++++++++++++++++++- tests/du/bind-mount-dir-cycle-v2.sh | 38 +++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 1 deletion(-) create mode 100755 tests/du/bind-mount-dir-cycle-v2.sh diff --git a/src/du.c b/src/du.c index ba20120..a145a4c 100644 --- a/src/du.c +++ b/src/du.c @@ -419,6 +419,25 @@ print_size (const struct duinfo *pdui, const char *string) fflush (stdout); } +/* This function checks whether any of the directories in the cycle that + * fts detected is a mount point. */ + +static bool +mount_point_in_fts_cycle(FTSENT *ent) +{ + FTSENT *cycle_ent = ent->fts_cycle; + + while(ent && ent != cycle_ent) + { + if (di_set_lookup(di_mnt, ent->fts_statp->st_dev, ent->fts_statp->st_ino) > 0) + { + return true; + } + ent = ent->fts_parent; + } + return false; +} + /* This function is called once for every file system object that fts encounters. fts does a depth-first traversal. This function knows that and accumulates per-directory totals based on changes in @@ -516,7 +535,7 @@ process_file (FTS *fts, FTSENT *ent) case FTS_DC: /* If not following symlinks and not a (bind) mount point. */ if (cycle_warning_required (fts, ent) - && ! di_set_lookup (di_mnt, sb->st_dev, sb->st_ino)) + && ! mount_point_in_fts_cycle (ent)) { emit_cycle_warning (file); return false; diff --git a/tests/du/bind-mount-dir-cycle-v2.sh b/tests/du/bind-mount-dir-cycle-v2.sh new file mode 100755 index 0000000..384d3e2 --- /dev/null +++ b/tests/du/bind-mount-dir-cycle-v2.sh @@ -0,0 +1,38 @@ +#!/bin/sh +# Check that du can handle sub-bind-mounts cycles as well. + +# Copyright (C) 2014 Free Software foundation, Inc. + +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. + +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. + +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + +. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src +print_ver_ du +require_root_ + +cleanup_() { umount a/b/c; } + +mkdir -p a/b/c || framework_failure_ +mount --bind a a/b/c \ + || skip_ "This test requires mount with a working --bind option." + +echo a/b/c > exp || framework_failure_ +echo a/b >> exp || framework_failure_ + +du a/b > out 2> err || fail=1 +sed 's/^[0-9][0-9]*\t//' out > k && mv k out + +compare /dev/null err || fail=1 +compare exp out || fail=1 + +Exit $fail -- 1.9.3
