Enabling btrfs tracepoints leads to instant crash, as reported. The wq callbacks could free the memory and the tracepoints started to dereference the members to get to fs_info. The proposed fix https://marc.info/?l=linux-btrfs&m=148172436722606&w=2 removed the tracepoints but we could preserve them by passing only the required data in a safe way. Fixes: bc074524e123 ("btrfs: prefix fsid to all trace events") CC: stable@xxxxxxxxxxxxxxx # 4.8+ Reported-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> --- fs/btrfs/async-thread.c | 15 +++++++++++---- include/trace/events/btrfs.h | 22 +++++++++++++--------- 2 files changed, 24 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 63d197724519..ff0b0be92d61 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -273,6 +273,8 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) unsigned long flags; while (1) { + void *wtag; + spin_lock_irqsave(lock, flags); if (list_empty(list)) break; @@ -299,11 +301,13 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) spin_unlock_irqrestore(lock, flags); /* - * we don't want to call the ordered free functions - * with the lock held though + * We don't want to call the ordered free functions with the + * lock held though. Save the work as tag for the trace event, + * because the callback could free the structure. */ + wtag = work; work->ordered_free(work); - trace_btrfs_all_work_done(work); + trace_btrfs_all_work_done(wq->fs_info, wtag); } spin_unlock_irqrestore(lock, flags); } @@ -311,6 +315,7 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) static void normal_work_helper(struct btrfs_work *work) { struct __btrfs_workqueue *wq; + void *wtag; int need_order = 0; /* @@ -324,6 +329,8 @@ static void normal_work_helper(struct btrfs_work *work) if (work->ordered_func) need_order = 1; wq = work->wq; + /* Safe for tracepoints in case work gets freed by the callback */ + wtag = work; trace_btrfs_work_sched(work); thresh_exec_hook(wq); @@ -333,7 +340,7 @@ static void normal_work_helper(struct btrfs_work *work) run_ordered_work(wq); } if (!need_order) - trace_btrfs_all_work_done(work); + trace_btrfs_all_work_done(wq->fs_info, wtag); } void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t uniq_func, diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index c14bed4ab097..b09225c77676 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -1157,22 +1157,26 @@ DECLARE_EVENT_CLASS(btrfs__work, __entry->func, __entry->ordered_func, __entry->ordered_free) ); -/* For situiations that the work is freed */ +/* + * For situiations when the work is freed, we pass fs_info and a tag that that + * matches address of the work structure so it can be paired with the + * scheduling event. + */ DECLARE_EVENT_CLASS(btrfs__work__done, - TP_PROTO(struct btrfs_work *work), + TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag), - TP_ARGS(work), + TP_ARGS(fs_info, wtag), TP_STRUCT__entry_btrfs( - __field( void *, work ) + __field( void *, wtag ) ), - TP_fast_assign_btrfs(btrfs_work_owner(work), - __entry->work = work; + TP_fast_assign_btrfs(fs_info, + __entry->wtag = wtag; ), - TP_printk_btrfs("work->%p", __entry->work) + TP_printk_btrfs("work->%p", __entry->wtag) ); DEFINE_EVENT(btrfs__work, btrfs_work_queued, @@ -1191,9 +1195,9 @@ DEFINE_EVENT(btrfs__work, btrfs_work_sched, DEFINE_EVENT(btrfs__work__done, btrfs_all_work_done, - TP_PROTO(struct btrfs_work *work), + TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag), - TP_ARGS(work) + TP_ARGS(fs_info, wtag) ); DEFINE_EVENT(btrfs__work, btrfs_ordered_sched, -- 2.10.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html