Submitted by: DJ Lucas (dj_AT_linuxfromscratch_DOT_org) Date: 2016-01-16 Initial Package Version: 8.24 Upstream Status: Applied Origin: https://lists.gnu.org/archive/html/bug-coreutils/2015-10/txtlhdkw0E4Uv.txt Description: Fixes race condition. See thread begining at https://lists.gnu.org/archive/html/bug-coreutils/2015-09/msg00013.html for a detailed eplanation >From 07ca8a227e04f9fb7bb0b21968056a562b8c2f83 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?P=C3=A1draig=20Brady?= Date: Thu, 2 Jul 2015 08:41:25 +0100 Subject: [PATCH] tail: handle kernel dentry unlink race MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Avoid the intermittent loss of "... has become inaccessible" messages. That would cause tests/tail-2/assert.sh to fail sometimes, mainly on uniprocessor systems. * src/tail.c (tail_forever_inotify): Also monitor IN_DELETE events on the directory, to avoid a dentry unlink()..open() race, where the open() on the deleted file was seen to succeed after an, unlink() and a subsequent IN_ATTRIB, was sent to tail. Note an IN_ATTRIB is sent on the monitored file to indicate the change in number of links, and we can't just use a decrease in the number of links to determine the file being unlinked, due to the possibility of the file having multiple links. Reported by Assaf Gordon and Ludovic Courtès. Fixes http://bugs.gnu.org/21460 --- src/tail.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/src/tail.c b/src/tail.c index f916d74..7a34b0b 100644 --- a/src/tail.c +++ b/src/tail.c @@ -1429,8 +1429,8 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, /* It's fine to add the same directory more than once. In that case the same watch descriptor is returned. */ f[i].parent_wd = inotify_add_watch (wd, dirlen ? f[i].name : ".", - (IN_CREATE | IN_MOVED_TO - | IN_ATTRIB)); + (IN_CREATE | IN_DELETE + | IN_MOVED_TO | IN_ATTRIB)); f[i].name[dirlen] = prev; @@ -1619,9 +1619,16 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, fspec = &(f[j]); - /* Adding the same inode again will look up any existing wd. */ - int new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask); - if (new_wd < 0) + int new_wd = -1; + bool deleting = !! (ev->mask & IN_DELETE); + + if (! deleting) + { + /* Adding the same inode again will look up any existing wd. */ + new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask); + } + + if (! deleting && new_wd < 0) { if (errno == ENOSPC || errno == ENOMEM) { @@ -1641,7 +1648,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, /* This will be false if only attributes of file change. */ bool new_watch = fspec->wd < 0 || new_wd != fspec->wd; - if (new_watch) + if (! deleting && new_watch) { if (0 <= fspec->wd) { @@ -1683,7 +1690,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, if (! fspec) continue; - if (ev->mask & (IN_ATTRIB | IN_DELETE_SELF | IN_MOVE_SELF)) + if (ev->mask & (IN_ATTRIB | IN_DELETE | IN_DELETE_SELF | IN_MOVE_SELF)) { /* Note for IN_MOVE_SELF (the file we're watching has been clobbered via a rename) we leave the watch -- 2.5.0