mirror of https://gitee.com/openkylin/linux.git
drbd: fix race on meta-data update, addendum
addendum to baa33ae4eaa4477b60af7c434c0ddd1d182c1ae7 The race: drbd_md_sync() if (!test_and_clear_bit(MD_DIRTY, &mdev->flags)) return; ==> RACE with drbd_md_mark_dirty() rearming the timer. del_timer(&mdev->md_sync_timer); Fixed by moving the del_timer before the test_and_clear_bit. Additionally only rearm the timer in drbd_md_mark_dirty, if MD_DIRTY was not already set, reduce the grace period from five to one second, and add an ifdef'ed debuging aid to find code paths missing an explicit drbd_md_sync, if any, as those are the only relevant ones for this race. Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com> Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
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@ -975,6 +975,12 @@ struct drbd_conf {
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md_sync_work;
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md_sync_work;
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struct timer_list resync_timer;
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struct timer_list resync_timer;
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struct timer_list md_sync_timer;
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struct timer_list md_sync_timer;
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#ifdef DRBD_DEBUG_MD_SYNC
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struct {
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unsigned int line;
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const char* func;
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} last_md_mark_dirty;
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#endif
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/* Used after attach while negotiating new disk state. */
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/* Used after attach while negotiating new disk state. */
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union drbd_state new_state_tmp;
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union drbd_state new_state_tmp;
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@ -1253,7 +1259,13 @@ extern void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local)
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extern void drbd_md_set_flag(struct drbd_conf *mdev, int flags) __must_hold(local);
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extern void drbd_md_set_flag(struct drbd_conf *mdev, int flags) __must_hold(local);
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extern void drbd_md_clear_flag(struct drbd_conf *mdev, int flags)__must_hold(local);
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extern void drbd_md_clear_flag(struct drbd_conf *mdev, int flags)__must_hold(local);
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extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
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extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
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#ifndef DRBD_DEBUG_MD_SYNC
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extern void drbd_md_mark_dirty(struct drbd_conf *mdev);
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extern void drbd_md_mark_dirty(struct drbd_conf *mdev);
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#else
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#define drbd_md_mark_dirty(m) drbd_md_mark_dirty_(m, __LINE__ , __func__ )
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extern void drbd_md_mark_dirty_(struct drbd_conf *mdev,
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unsigned int line, const char *func);
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#endif
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extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
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extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
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int (*io_fn)(struct drbd_conf *),
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int (*io_fn)(struct drbd_conf *),
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void (*done)(struct drbd_conf *, int),
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void (*done)(struct drbd_conf *, int),
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@ -3402,9 +3402,10 @@ void drbd_md_sync(struct drbd_conf *mdev)
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sector_t sector;
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sector_t sector;
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int i;
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int i;
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del_timer(&mdev->md_sync_timer);
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/* timer may be rearmed by drbd_md_mark_dirty() now. */
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if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
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if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
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return;
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return;
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del_timer(&mdev->md_sync_timer);
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/* We use here D_FAILED and not D_ATTACHING because we try to write
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/* We use here D_FAILED and not D_ATTACHING because we try to write
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* metadata even if we detach due to a disk failure! */
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* metadata even if we detach due to a disk failure! */
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@ -3529,12 +3530,22 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
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* the meta-data super block. This function sets MD_DIRTY, and starts a
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* the meta-data super block. This function sets MD_DIRTY, and starts a
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* timer that ensures that within five seconds you have to call drbd_md_sync().
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* timer that ensures that within five seconds you have to call drbd_md_sync().
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*/
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*/
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#ifdef DRBD_DEBUG_MD_SYNC
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void drbd_md_mark_dirty_(struct drbd_conf *mdev, unsigned int line, const char *func)
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{
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if (!test_and_set_bit(MD_DIRTY, &mdev->flags)) {
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mod_timer(&mdev->md_sync_timer, jiffies + HZ);
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mdev->last_md_mark_dirty.line = line;
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mdev->last_md_mark_dirty.func = func;
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}
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}
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#else
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void drbd_md_mark_dirty(struct drbd_conf *mdev)
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void drbd_md_mark_dirty(struct drbd_conf *mdev)
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{
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{
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set_bit(MD_DIRTY, &mdev->flags);
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if (!test_and_set_bit(MD_DIRTY, &mdev->flags))
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mod_timer(&mdev->md_sync_timer, jiffies + 5*HZ);
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mod_timer(&mdev->md_sync_timer, jiffies + HZ);
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}
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}
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#endif
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static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
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static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
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{
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{
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@ -3775,8 +3786,11 @@ static void md_sync_timer_fn(unsigned long data)
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static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused)
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static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused)
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{
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{
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dev_warn(DEV, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
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dev_warn(DEV, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
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#ifdef DEBUG
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dev_warn(DEV, "last md_mark_dirty: %s:%u\n",
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mdev->last_md_mark_dirty.func, mdev->last_md_mark_dirty.line);
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#endif
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drbd_md_sync(mdev);
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drbd_md_sync(mdev);
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return 1;
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return 1;
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}
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}
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