From 5dde5952b696d0f97730ed45271d21d9e50b32f7 Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Wed, 13 Jul 2011 10:48:46 -0500 Subject: [PATCH] xfs [stable only]: restart busy extent search after node removal A user on #xfs reported that a log replay was oopsing in __rb_rotate_left() with a null pointer deref, and provided an xfs_metadump image for reproduction and testing. I traced this down to the fact that in xfs_alloc_busy_insert(), we erased a node with rb_erase() when the new node overlapped, but left the erased node specified as the parent node for the new insertion. So when we try to insert a new node with an erased node as its parent, obviously things go very wrong. Upstream, 97d3ac75e5e0ebf7ca38ae74cebd201c09b97ab2 xfs: exact busy extent tracking actually fixed this, but as part of a much larger change. Here's the relevant code from that commit: * We also need to restart the busy extent search from the * tree root, because erasing the node can rearrange the * tree topology. */ rb_erase(&busyp->rb_node, &pag->pagb_tree); busyp->length = 0; return false; We can do essentially the same thing to older codebases by restarting the tree search after the erase. This should apply to .35.y through .39.y, and was tested on .39 with the oopsing replay reproducer. Signed-off-by: Eric Sandeen Reviewed-by: Dave Chinner Reviewed-by: Alex Elder Signed-off-by: Greg Kroah-Hartman --- fs/xfs/xfs_alloc.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c index 27d64d752eab..a892ed905423 100644 --- a/fs/xfs/xfs_alloc.c +++ b/fs/xfs/xfs_alloc.c @@ -2610,6 +2610,12 @@ restart: new->bno + new->length) - min(busyp->bno, new->bno); new->bno = min(busyp->bno, new->bno); + /* + * Start the search over from the tree root, because + * erasing the node can rearrange the tree topology. + */ + spin_unlock(&pag->pagb_lock); + goto restart; } else busyp = NULL; -- 2.39.5