On 03/02/15 23:30, Pádraig Brady wrote: > On 03/02/15 22:04, Stephane Chazelas wrote: >> Hello, >> >> On Linux, when inotify is used, >> >> tail -f file >> >> follows a file only until it's renamed. After it is renamed, the >> inotify watch is removed, which means tail sits there doing >> nothing and any further modifications to the file are ignored. >> >> To reproduce: >> >> echo 1 > file >> tail -f file & >> exec 3>> file >> echo 2 >&3 >> sleep 1 >> mv file file2 >> sleep 1 >> echo 3 >&3 >> sleep 1 >> : > file2 >> >> "3" is not displayed. No message about the file being truncated >> either. >> >> Work arounds: >> >> tail ---disable-inotify -f file >> tail -f < file # effectively disables inotify >> >> or rename the file with a link() followed by an unlink() >> ln file newfile && rm -f file >> >> Note that the IN_DELETED_SELF event is not reached in >> follow-descriptor mode because tail has the file open preventing >> it from being deleted even after it's unlinked from the last >> directory. >> >> Patch attached (on the current git head). > > Ouch. The patch makes sense on first glance, > and all existing tests pass with it. > I'll check some more and add a test.
Sorry for the delay. I'll apply the attached in your name soon. thanks, Pádraig.
>From 9c23049e17a76f4ec8f38c04b088f149a49b4851 Mon Sep 17 00:00:00 2001 From: Stephane Chazelas <[email protected]> Date: Tue, 3 Feb 2015 21:22:06 +0000 Subject: [PATCH] tail: fix -f to follow changes after a rename * src/tail.c (tail_forever_inotify): Only monitor write()s and truncate()s to files in --follow=descriptor mode, thus avoiding the bug where we removed the watch on renamed files. Also adjust the inotify event processing code which that is now significant only in --follow=name mode. * tests/tail-2/f-vs-rename.sh: A new test. * tests/local.mk: Reference the new test. * NEWS: Mention the bug. Fixes http://bugs.gnu.org/19760 --- NEWS | 3 +++ src/tail.c | 31 +++++++++++++-------------- tests/local.mk | 1 + tests/tail-2/f-vs-rename.sh | 51 +++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 69 insertions(+), 17 deletions(-) create mode 100755 tests/tail-2/f-vs-rename.sh diff --git a/NEWS b/NEWS index 81031c6..214db08 100644 --- a/NEWS +++ b/NEWS @@ -39,6 +39,9 @@ GNU coreutils NEWS -*- outline -*- resources with many files, or with -F if files were replaced many times. [bug introduced in coreutils-7.5] + tail -f continues to follow changes to a file even after it's renamed. + [bug introduced in coreutils-7.5] + ** New features chroot accepts the new --skip-chdir option to not change the working directory diff --git a/src/tail.c b/src/tail.c index c5380cb..f75d7a9 100644 --- a/src/tail.c +++ b/src/tail.c @@ -159,13 +159,6 @@ struct File_spec uintmax_t n_unchanged_stats; }; -#if HAVE_INOTIFY -/* The events mask used with inotify on files. This mask is not used on - directories. */ -static const uint32_t inotify_wd_mask = (IN_MODIFY | IN_ATTRIB - | IN_DELETE_SELF | IN_MOVE_SELF); -#endif - /* Keep trying to open a file even if it is inaccessible when tail starts or if it becomes inaccessible later -- useful only with -f. */ static bool reopen_inaccessible_files; @@ -1390,6 +1383,13 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, if (! wd_to_name) xalloc_die (); + /* The events mask used with inotify on files (not directories). */ + uint32_t inotify_wd_mask = IN_MODIFY; + /* TODO: Perhaps monitor these events in Follow_descriptor mode also, + to tag reported file names with "deleted", "moved" etc. */ + if (follow_mode == Follow_name) + inotify_wd_mask |= (IN_ATTRIB | IN_DELETE_SELF | IN_MOVE_SELF); + /* Add an inotify watch for each watched file. If -F is specified then watch its parent directory too, in this way when they re-appear we can add them again to the watch list. */ @@ -1641,20 +1641,17 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, if (ev->mask & (IN_ATTRIB | IN_DELETE_SELF | IN_MOVE_SELF)) { - /* For IN_DELETE_SELF, we always want to remove the watch. - However, for IN_MOVE_SELF (the file we're watching has - been clobbered via a rename), when tailing by NAME, we - must continue to watch the file. It's only when following - by file descriptor that we must remove the watch. */ - if ((ev->mask & IN_DELETE_SELF) - || ((ev->mask & IN_MOVE_SELF) - && follow_mode == Follow_descriptor)) + /* Note for IN_MOVE_SELF (the file we're watching has + been clobbered via a rename) we leave the watch + in place since it may still be part of the set + of watched names. */ + if (ev->mask & IN_DELETE_SELF) { inotify_rm_watch (wd, fspec->wd); hash_delete (wd_to_name, fspec); } - if (follow_mode == Follow_name) - recheck (fspec, false); + + recheck (fspec, false); continue; } diff --git a/tests/local.mk b/tests/local.mk index 56cba69..1be31ad 100644 --- a/tests/local.mk +++ b/tests/local.mk @@ -171,6 +171,7 @@ all_tests = \ tests/tail-2/inotify-hash-abuse2.sh \ tests/tail-2/F-vs-missing.sh \ tests/tail-2/F-vs-rename.sh \ + tests/tail-2/f-vs-rename.sh \ tests/tail-2/inotify-rotate.sh \ tests/tail-2/inotify-rotate-resources.sh \ tests/chmod/no-x.sh \ diff --git a/tests/tail-2/f-vs-rename.sh b/tests/tail-2/f-vs-rename.sh new file mode 100755 index 0000000..efb0a40 --- /dev/null +++ b/tests/tail-2/f-vs-rename.sh @@ -0,0 +1,51 @@ +#!/bin/sh +# demonstrate that tail -f works when renaming the tailed files +# Before coreutils-8.24, tail -f a would stop tracking additions to b +# after "mv a b". + +# Copyright (C) 2015 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_ tail + +touch a || framework_failure_ + +debug='---disable-inotify' +debug= +tail $debug -f -s.1 a > out 2>&1 & pid=$! + +check_tail_output() +{ + local delay="$1" + grep "$tail_re" out > /dev/null || + { sleep $delay; return 1; } +} + +# Wait up to 12.7s for tail to start +echo x > a +tail_re='^x$' retry_delay_ check_tail_output .1 7 || fail=1 + +mv a b || fail=1 + +echo y >> b +# Wait up to 12.7s for "y" to appear in the output: +tail_re='^y$' retry_delay_ check_tail_output .1 7 || fail=1 + +kill $pid + +wait + +Exit $fail -- 2.1.0
