block: discard bdi_unregister() in favour of bdi_destroy()

bdi_unregister() now contains very little functionality.

It contains a "WARN_ON" if bdi->dev is NULL.  This warning is of no
real consequence as bdi->dev isn't needed by anything else in the function,
and it triggers if
   blk_cleanup_queue() -> bdi_destroy()
is called before bdi_unregister, which happens since
  Commit: 6cd18e711dd8 ("block: destroy bdi before blockdev is unregistered.")

So this isn't wanted.

It also calls bdi_set_min_ratio().  This needs to be called after
writes through the bdi have all been flushed, and before the bdi is destroyed.
Calling it early is better than calling it late as it frees up a global
resource.

Calling it immediately after bdi_wb_shutdown() in bdi_destroy()
perfectly fits these requirements.

So bdi_unregister() can be discarded with the important content moved to
bdi_destroy(), as can the
  writeback_bdi_unregister
event which is already not used.

Reported-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org (v4.0)
Fixes: c4db59d31e39 ("fs: don't reassign dirty inodes to default_backing_dev_info")
Fixes: 6cd18e711dd8 ("block: destroy bdi before blockdev is unregistered.")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Nicholas Moulin <nicholas.w.moulin@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/genhd.c b/block/genhd.c
index 0a536dc05f3b559d6d04c1e819d65290f96f7c35..666e11b8398378d145552b18e51c190c18847a9f 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -653,7 +653,6 @@ void del_gendisk(struct gendisk *disk)
        disk->flags &= ~GENHD_FL_UP;
 
        sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
-       bdi_unregister(&disk->queue->backing_dev_info);
        blk_unregister_queue(disk);
        blk_unregister_region(disk_devt(disk), disk->minors);
 

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index aff923ae8c4b963272563759b9ac52ad55778bd0..d87d8eced06407c59c6d231f9e707bdcc398ce52 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -116,7 +116,6 @@ __printf(3, 4)
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                const char *fmt, ...);
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
-void bdi_unregister(struct backing_dev_info *bdi);
 int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
                        enum wb_reason reason);

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 880dd74371729939a0179ef3dfd487e1fa017838..c178d13d6f4c0cb51d441c59e7b4975a1913ed3e 100644 (file)
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -250,7 +250,6 @@ DEFINE_EVENT(writeback_class, name, \
 DEFINE_WRITEBACK_EVENT(writeback_nowork);
 DEFINE_WRITEBACK_EVENT(writeback_wake_background);
 DEFINE_WRITEBACK_EVENT(writeback_bdi_register);
-DEFINE_WRITEBACK_EVENT(writeback_bdi_unregister);
 
 DECLARE_EVENT_CLASS(wbc_class,
        TP_PROTO(struct writeback_control *wbc, struct backing_dev_info *bdi),

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 6dc4580df2af040b10bc10a5f9c423becc3ff47e..000e7b3b9896f2a9479687befd2442c43193614e 100644 (file)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -359,23 +359,6 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
        flush_delayed_work(&bdi->wb.dwork);
 }
 
-/*
- * Called when the device behind @bdi has been removed or ejected.
- *
- * We can't really do much here except for reducing the dirty ratio at
- * the moment.  In the future we should be able to set a flag so that
- * the filesystem can handle errors at mark_inode_dirty time instead
- * of only at writeback time.
- */
-void bdi_unregister(struct backing_dev_info *bdi)
-{
-       if (WARN_ON_ONCE(!bdi->dev))
-               return;
-
-       bdi_set_min_ratio(bdi, 0);
-}
-EXPORT_SYMBOL(bdi_unregister);
-
 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 {
        memset(wb, 0, sizeof(*wb));
@@ -443,6 +426,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
        int i;
 
        bdi_wb_shutdown(bdi);
+       bdi_set_min_ratio(bdi, 0);
 
        WARN_ON(!list_empty(&bdi->work_list));
        WARN_ON(delayed_work_pending(&bdi->wb.dwork));