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authorDavid Teigland <teigland@redhat.com>2007-09-28 00:53:38 +0400
committerSteven Whitehouse <swhiteho@redhat.com>2007-10-10 11:56:38 +0400
commitc36258b5925e6cf6bf72904635100593573bfcff (patch)
tree565f1ce29a7f8a2cd1c25f2d36c932727adbdbc2 /fs/dlm/recoverd.c
parentb434eda6fda5bcdcc2dd918e5ffbf7184f2d4e17 (diff)
downloadlinux-c36258b5925e6cf6bf72904635100593573bfcff.tar.xz
[DLM] block dlm_recv in recovery transition
Introduce a per-lockspace rwsem that's held in read mode by dlm_recv threads while working in the dlm. This allows dlm_recv activity to be suspended when the lockspace transitions to, from and between recovery cycles. The specific bug prompting this change is one where an in-progress recovery cycle is aborted by a new recovery cycle. While dlm_recv was processing a recovery message, the recovery cycle was aborted and dlm_recoverd began cleaning up. dlm_recv decremented recover_locks_count on an rsb after dlm_recoverd had reset it to zero. This is fixed by suspending dlm_recv (taking write lock on the rwsem) before aborting the current recovery. The transitions to/from normal and recovery modes are simplified by using this new ability to block dlm_recv. The switch from normal to recovery mode means dlm_recv goes from processing locking messages, to saving them for later, and vice versa. Races are avoided by blocking dlm_recv when setting the flag that switches between modes. Signed-off-by: David Teigland <teigland@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/dlm/recoverd.c')
-rw-r--r--fs/dlm/recoverd.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/fs/dlm/recoverd.c b/fs/dlm/recoverd.c
index 66575997861c..4b89e20eebe7 100644
--- a/fs/dlm/recoverd.c
+++ b/fs/dlm/recoverd.c
@@ -24,19 +24,28 @@
/* If the start for which we're re-enabling locking (seq) has been superseded
- by a newer stop (ls_recover_seq), we need to leave locking disabled. */
+ by a newer stop (ls_recover_seq), we need to leave locking disabled.
+
+ We suspend dlm_recv threads here to avoid the race where dlm_recv a) sees
+ locking stopped and b) adds a message to the requestqueue, but dlm_recoverd
+ enables locking and clears the requestqueue between a and b. */
static int enable_locking(struct dlm_ls *ls, uint64_t seq)
{
int error = -EINTR;
+ down_write(&ls->ls_recv_active);
+
spin_lock(&ls->ls_recover_lock);
if (ls->ls_recover_seq == seq) {
set_bit(LSFL_RUNNING, &ls->ls_flags);
+ /* unblocks processes waiting to enter the dlm */
up_write(&ls->ls_in_recovery);
error = 0;
}
spin_unlock(&ls->ls_recover_lock);
+
+ up_write(&ls->ls_recv_active);
return error;
}