Hi Jan,
> How about adding the attached patch to the series? With it applied we
> would have all busyloop prevention done in the same way.
Sure. It looks good.
> + pr_warn_ratelimited("mm: Possible busyloop in data writeback "
> + "(bdi %s nr_pages %ld sync_mode %d kupdate %d "
> + "background %d)\n",
> + wb->bdi->name, work->nr_pages, work->sync_mode,
> + work->for_kupdate, work->for_background);
I'll change the last two fields to the newly introduced writeback "reason":
pr_warn_ratelimited("mm: Possible busyloop in data writeback "
"(bdi %s nr_pages %ld sync_mode %d reason %s)\n",
wb->bdi->name, work->nr_pages, work->sync_mode,
wb_reason_name[work->reason]);
btw, with the I_SYNC case converted, it's actually no longer necessary
to keep a standalone b_more_io_wait. It should still be better to keep
the list and the above error check for catching possible errors and
the flexibility of adding policies like "don't retry possible blocked
inodes in N seconds as long as there are other inodes to work with".
The below diff only intends to show the _possibility_ to remove
b_more_io_wait:
--- linux-next.orig/fs/fs-writeback.c 2011-10-21 18:25:25.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-10-21 18:27:41.000000000 +0800
@@ -235,20 +235,7 @@ static void requeue_io(struct inode *ino
list_move(&inode->i_wb_list, &wb->b_more_io);
}
-/*
- * The inode should be retried in an opportunistic way.
- *
- * The only difference between b_more_io and b_more_io_wait is:
- * wb_writeback() won't quit as long as b_more_io is not empty. When
- * wb_writeback() quit on empty b_more_io and non-empty b_more_io_wait,
- * the kupdate work will wakeup more frequently to retry the inodes in
- * b_more_io_wait.
- */
-static void requeue_io_wait(struct inode *inode, struct bdi_writeback *wb)
-{
- assert_spin_locked(&wb->list_lock);
- list_move(&inode->i_wb_list, &wb->b_more_io_wait);
-}
+#define requeue_io_wait(inode, wb) requeue_io(inode, wb)
static void inode_sync_complete(struct inode *inode)
{
@@ -798,21 +785,8 @@ static long wb_writeback(struct bdi_writ
* mean the overall work is done. So we keep looping as long
* as made some progress on cleaning pages or inodes.
*/
- if (progress)
- continue;
- /*
- * No more inodes for IO, bail
- */
- if (list_empty(&wb->b_more_io))
+ if (!progress)
break;
- /*
- * Nothing written but some inodes were moved to b_more_io.
- * This should not happen as we can easily busyloop.
- */
- pr_warn_ratelimited("mm: Possible busyloop in data writeback "
- "(bdi %s nr_pages %ld sync_mode %d reason %s)\n",
- wb->bdi->name, work->nr_pages, work->sync_mode,
- wb_reason_name[work->reason]);
}
spin_unlock(&wb->list_lock);
Thanks,
Fengguang
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