Re: disk revalidation updates and OOM

[Christoph Hellwig <hch@lst.de>]

On Tue, Mar 17, 2020 at 04:50:11PM +0800, He Zhe wrote:
> >> With my build fix applied, the issue is triggered since 142fe8f.
> >> And I can see the endless loop of invalidate and revalidate...
> > Thanks.  Can you test the patch below that restores the previous
> > rather odd behavior of not clearing the capacity to 0 if partition
> > scanning is not enabled?
> 
> This fixes the issue. I also validated it on v5.6-rc6.

Can you check this slight variant that only skips the capacity
change for removable devices given that IIRC you reported the problem
with a legacy ide-cd device?


diff --git a/fs/block_dev.c b/fs/block_dev.c
index 69bf2fb6f7cd..3212ac85d493 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1520,10 +1520,14 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
 	if (ret)
 		return ret;
 
-	if (invalidate)
-		set_capacity(disk, 0);
-	else if (disk->fops->revalidate_disk)
-		disk->fops->revalidate_disk(disk);
+	if (invalidate) {
+		if (!(disk->flags & GENHD_FL_REMOVABLE) ||
+		    disk_part_scan_enabled(disk))
+			set_capacity(disk, 0);
+	} else {
+		if (disk->fops->revalidate_disk)
+			disk->fops->revalidate_disk(disk);
+	}
 
 	check_disk_size_change(disk, bdev, !invalidate);