ca38f0b091
- improve mount location error reporting. - fix paged query more results check. - fix dumpmaps not reading maps. - fix result null check in read_one_map(). - Fix LDAP result leaks on error paths. - code analysis fixes 1. - fix not bind mounting local filesystem. - update dir map-type patch for changed patch order. - fix wait for master source mutex. - fix submount shutdown race - fix fix map source check in file lookup. - add disable move mount configure option.
142 lines
3.9 KiB
Diff
142 lines
3.9 KiB
Diff
autofs-5.0.6 - fix submount shutdown race
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From: Ian Kent <ikent@redhat.com>
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Shutdown of submounts is problematic because the kernel doesn't
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know when they are going away and so cannot block path walks
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while they shut down. After aquiring the locks that cause mount
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requests to wait, the daemon checks if the submount is active before
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finally umounting it. If the mount is found to be busy the shutdown
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is abandoned and the submount returned to a ready state.
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But, if a mount request arrives at the same time as the daemon is
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attempting to aquire these locks pthreads appears to become confused
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and blocks. So change to using the try version of the lock call and
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handling the return appropriately.
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---
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CHANGELOG | 1 +
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daemon/automount.c | 76 ++++++++++++++++++++++++++++++++++++++++------------
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2 files changed, 60 insertions(+), 17 deletions(-)
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diff --git a/CHANGELOG b/CHANGELOG
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index cac450f..cb9ac75 100644
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--- a/CHANGELOG
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+++ b/CHANGELOG
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@@ -10,6 +10,7 @@
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- fix not bind mounting local filesystem.
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- add "dir" map-type.
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- fix wait for master source mutex.
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+- fix submount shutdown race.
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28/06/2011 autofs-5.0.6
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-----------------------
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diff --git a/daemon/automount.c b/daemon/automount.c
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index 376e965..4f3151f 100644
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--- a/daemon/automount.c
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+++ b/daemon/automount.c
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@@ -1495,6 +1495,41 @@ static void handle_mounts_cleanup(void *arg)
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return;
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}
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+static int submount_source_writelock_nested(struct autofs_point *ap)
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+{
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+ struct autofs_point *parent = ap->parent;
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+ int status;
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+
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+ status = pthread_rwlock_trywrlock(&parent->entry->source_lock);
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+ if (status)
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+ goto done;
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+
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+ mounts_mutex_lock(parent);
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+
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+ status = pthread_rwlock_trywrlock(&ap->entry->source_lock);
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+ if (status) {
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+ mounts_mutex_unlock(parent);
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+ master_source_unlock(parent->entry);
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+ }
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+
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+done:
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+ if (status && status != EBUSY) {
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+ logmsg("submount nested master_mapent source write lock failed");
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+ fatal(status);
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+ }
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+
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+ return status;
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+}
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+
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+static void submount_source_unlock_nested(struct autofs_point *ap)
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+{
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+ struct autofs_point *parent = ap->parent;
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+
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+ master_source_unlock(ap->entry);
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+ mounts_mutex_unlock(parent);
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+ master_source_unlock(parent->entry);
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+}
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+
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void *handle_mounts(void *arg)
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{
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struct startup_cond *suc;
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@@ -1565,23 +1600,32 @@ void *handle_mounts(void *arg)
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master_mutex_lock();
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if (ap->submount) {
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- master_source_writelock(ap->parent->entry);
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- mounts_mutex_lock(ap->parent);
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- }
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-
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- master_source_writelock(ap->entry);
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+ /*
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+ * If a mount request arrives before the locks are
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+ * aquired just return to ready state.
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+ */
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+ ret = submount_source_writelock_nested(ap);
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+ if (ret) {
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+ warn(ap->logopt,
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+ "can't shutdown submount: mount in progress");
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+ /* Return to ST_READY is done immediately */
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+ st_add_task(ap, ST_READY);
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+ master_mutex_unlock();
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+ pthread_setcancelstate(cur_state, NULL);
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+ continue;
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+ }
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+ } else
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+ master_source_writelock(ap->entry);
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if (ap->state != ST_SHUTDOWN) {
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if (!ap->submount)
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alarm_add(ap, ap->exp_runfreq);
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/* Return to ST_READY is done immediately */
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st_add_task(ap, ST_READY);
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- master_source_unlock(ap->entry);
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- if (ap->submount) {
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- mounts_mutex_unlock(ap->parent);
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- master_source_unlock(ap->parent->entry);
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- }
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-
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+ if (ap->submount)
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+ submount_source_unlock_nested(ap);
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+ else
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+ master_source_unlock(ap->entry);
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master_mutex_unlock();
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pthread_setcancelstate(cur_state, NULL);
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@@ -1621,12 +1665,10 @@ void *handle_mounts(void *arg)
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alarm_add(ap, ap->exp_runfreq);
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/* Return to ST_READY is done immediately */
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st_add_task(ap, ST_READY);
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- master_source_unlock(ap->entry);
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- if (ap->submount) {
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- mounts_mutex_unlock(ap->parent);
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- master_source_unlock(ap->parent->entry);
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- }
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-
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+ if (ap->submount)
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+ submount_source_unlock_nested(ap);
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+ else
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+ master_source_unlock(ap->entry);
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master_mutex_unlock();
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pthread_setcancelstate(cur_state, NULL);
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