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[PATCH] du now diagnoses cycles, rather than ignoring them
From: |
Jim Meyering |
Subject: |
[PATCH] du now diagnoses cycles, rather than ignoring them |
Date: |
Wed, 04 Nov 2009 22:22:41 +0100 |
[fall-out from the FTS vs. automount-changing-st_dev problem, ...]
While du ignoring cycles may not be an official "bug"
(in the sense that the POSIX du spec says nothing about cycles)
I think it deserves to be diagnosed and to provoke a nonzero exit status.
You can reproduce the problem by following these instructions on a
Fedora 12 system:
http://bugzilla.redhat.com/501848#c45
Then, do this:
$ ./du -s --exclude='/tmp/mnt/t*' --exclude '[os.fbvuxdiepljr]*' /tmp/mnt
./du: WARNING: Circular directory structure.
This almost certainly means that you have a corrupted file system.
NOTIFY YOUR SYSTEM MANAGER.
The following directory is part of the cycle:
`/tmp/mnt/home'
12 /tmp/mnt
[Exit 1]
[the exclusions are simply to make it run quickly,
by not traversing into directories that aren't relevant]
With the following patch, it prints the above diagnostic and fails.
Before, it would silently ignore everything under /tmp/mnt/home and exit 0.
BTW, the diagnostic (including trailing NL) is copied verbatim from remove.c.
As I write this, I now realize I should factor that out. Besides, the
other fts-using programs probably need a similar change.
Before this patch, it skipped /tmp/mnt/home because fts_read reported
FTS_DC (indicating a directory cycle) and process_file ignored that
problem. Here you can see the two directories with identical dev/inode
pairs:
$ stat --printf "%d %i %n\n" /tmp/mnt/home /tmp/mnt
24 2 /tmp/mnt/home
24 2 /tmp/mnt
That is due to a bug in the kernel.
The reproducer mentioned above is more invasive than usual,
so I'm going to refrain from adding a test.
>From 772a8448c936d85f531011b68eaf91248679e651 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Wed, 4 Nov 2009 22:01:52 +0100
Subject: [PATCH] du now diagnoses cycles, rather than ignoring them
* src/du.c (symlink_deref_bits): New global, decl moved from ...
(main): ...here.
(process_file): When fts detects a directory cycle that can't
be due to symlinks, report it and arrange to exit nonzero.
* NEWS (Bug fixes): Mention it.
---
NEWS | 3 +++
src/du.c | 28 +++++++++++++++++++++++-----
2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/NEWS b/NEWS
index 03ed83f..ffecd86 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,9 @@ GNU coreutils NEWS -*-
outline -*-
Even then, chcon may still be useful.
[bug introduced in coreutils-8.0]
+ du now diagnoses an ostensible directory cycle and arranges to exit nonzero.
+ Before, it would silently ignore the offending directory and all "contents."
+
env -u A=B now fails, rather than silently adding A to the
environment. Likewise, printenv A=B silently ignores the invalid
name. [the bugs date back to the initial implementation]
diff --git a/src/du.c b/src/du.c
index 9831a17..c684d1a 100644
--- a/src/du.c
+++ b/src/du.c
@@ -65,9 +65,12 @@ extern bool fts_debug;
/* Initial size of the hash table. */
#define INITIAL_TABLE_SIZE 103
+/* Select one of the three FTS_ options that control if/when
+ to follow a symlink. */
+static int symlink_deref_bits = FTS_PHYSICAL;
+
/* Hash structure for inode and device numbers. The separate entry
structure makes it easier to rehash "in place". */
-
struct entry
{
ino_t st_ino;
@@ -495,6 +498,25 @@ process_file (FTS *fts, FTSENT *ent)
ok = false;
break;
+ case FTS_DC: /* directory that causes cycles */
+ /* When dereferencing no symlinks, or when dereferencing only
+ those listed on the command line and we're not processing
+ a command-line argument, then a cycle is a serious problem. */
+ if (symlink_deref_bits == FTS_PHYSICAL
+ || (symlink_deref_bits == (FTS_COMFOLLOW | FTS_PHYSICAL)
+ && ent->fts_level != FTS_ROOTLEVEL))
+ {
+ error (0, 0, _("\
+WARNING: Circular directory structure.\n\
+This almost certainly means that you have a corrupted file system.\n\
+NOTIFY YOUR SYSTEM MANAGER.\n\
+The following directory is part of the cycle:\n %s\n"),
+ quote (ent->fts_path));
+ return false;
+ }
+ ok = true;
+ break;
+
default:
ok = true;
break;
@@ -661,10 +683,6 @@ main (int argc, char **argv)
/* Bit flags that control how fts works. */
int bit_flags = FTS_TIGHT_CYCLE_CHECK | FTS_DEFER_STAT;
- /* Select one of the three FTS_ options that control if/when
- to follow a symlink. */
- int symlink_deref_bits = FTS_PHYSICAL;
-
/* If true, display only a total for each argument. */
bool opt_summarize_only = false;
--
1.6.5.2.292.g1cda2
- [PATCH] du now diagnoses cycles, rather than ignoring them,
Jim Meyering <=