Subject: [merged] ocfs2-dlm-fix-lock-migration-crash.patch removed from -mm tree To: junxiao.bi@xxxxxxxxxx,jlbec@xxxxxxxxxxxx,mfasheh@xxxxxxxx,srinivas.eeda@xxxxxxxxxx,stable@xxxxxxxxxxxxxxx,sunil.mushran@xxxxxxxxx,wen.gang.wang@xxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Fri, 04 Apr 2014 12:30:05 -0700 The patch titled Subject: ocfs2: dlm: fix lock migration crash has been removed from the -mm tree. Its filename was ocfs2-dlm-fix-lock-migration-crash.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Junxiao Bi <junxiao.bi@xxxxxxxxxx> Subject: ocfs2: dlm: fix lock migration crash This issue was introduced by 800deef3 ("ocfs2: use list_for_each_entry where benefical") in 2007 where it replaced list_for_each with list_for_each_entry. The variable "lock" will point to invalid data if "tmpq" list is empty and a panic will be triggered due to this. Sunil advised reverting it back, but the old version was also not right. At the end of the outer for loop, that list_for_each_entry will also set "lock" to an invalid data, then in the next loop, if the "tmpq" list is empty, "lock" will be an stale invalid data and cause the panic. So reverting the list_for_each back and reset "lock" to NULL to fix this issue. Another concern is that this seemes can not happen because the "tmpq" list should not be empty. Let me describe how. old lock resource owner(node 1): migratation target(node 2): image there's lockres with a EX lock from node 2 in granted list, a NR lock from node x with convert_type EX in converting list. dlm_empty_lockres() { dlm_pick_migration_target() { pick node 2 as target as its lock is the first one in granted list. } dlm_migrate_lockres() { dlm_mark_lockres_migrating() { res->state |= DLM_LOCK_RES_BLOCK_DIRTY; wait_event(dlm->ast_wq, !dlm_lockres_is_dirty(dlm, res)); //after the above code, we can not dirty lockres any more, // so dlm_thread shuffle list will not run downconvert lock from EX to NR upconvert lock from NR to EX <<< migration may schedule out here, then <<< node 2 send down convert request to convert type from EX to <<< NR, then send up convert request to convert type from NR to <<< EX, at this time, lockres granted list is empty, and two locks <<< in the converting list, node x up convert lock followed by <<< node 2 up convert lock. // will set lockres RES_MIGRATING flag, the following // lock/unlock can not run dlm_lockres_release_ast(dlm, res); } dlm_send_one_lockres() dlm_process_recovery_data() for (i=0; i<mres->num_locks; i++) if (ml->node == dlm->node_num) for (j = DLM_GRANTED_LIST; j <= DLM_BLOCKED_LIST; j++) { list_for_each_entry(lock, tmpq, list) if (lock) break; <<< lock is invalid as grant list is empty. } if (lock->ml.node != ml->node) BUG() >>> crash here } I see the above locks status from a vmcore of our internal bug. Signed-off-by: Junxiao Bi <junxiao.bi@xxxxxxxxxx> Reviewed-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx> Cc: Sunil Mushran <sunil.mushran@xxxxxxxxx> Reviewed-by: Srinivas Eeda <srinivas.eeda@xxxxxxxxxx> Cc: Joel Becker <jlbec@xxxxxxxxxxxx> Cc: Mark Fasheh <mfasheh@xxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ocfs2/dlm/dlmrecovery.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff -puN fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-lock-migration-crash fs/ocfs2/dlm/dlmrecovery.c --- a/fs/ocfs2/dlm/dlmrecovery.c~ocfs2-dlm-fix-lock-migration-crash +++ a/fs/ocfs2/dlm/dlmrecovery.c @@ -1750,13 +1750,13 @@ static int dlm_process_recovery_data(str struct dlm_migratable_lockres *mres) { struct dlm_migratable_lock *ml; - struct list_head *queue; + struct list_head *queue, *iter; struct list_head *tmpq = NULL; struct dlm_lock *newlock = NULL; struct dlm_lockstatus *lksb = NULL; int ret = 0; int i, j, bad; - struct dlm_lock *lock = NULL; + struct dlm_lock *lock; u8 from = O2NM_MAX_NODES; unsigned int added = 0; __be64 c; @@ -1791,14 +1791,16 @@ static int dlm_process_recovery_data(str /* MIGRATION ONLY! */ BUG_ON(!(mres->flags & DLM_MRES_MIGRATION)); + lock = NULL; spin_lock(&res->spinlock); for (j = DLM_GRANTED_LIST; j <= DLM_BLOCKED_LIST; j++) { tmpq = dlm_list_idx_to_ptr(res, j); - list_for_each_entry(lock, tmpq, list) { - if (lock->ml.cookie != ml->cookie) - lock = NULL; - else + list_for_each(iter, tmpq) { + lock = list_entry(iter, + struct dlm_lock, list); + if (lock->ml.cookie == ml->cookie) break; + lock = NULL; } if (lock) break; _ Patches currently in -mm which might be from junxiao.bi@xxxxxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html