On Fri, Mar 16, 2018 at 02:36:27PM -0400, jeffm@xxxxxxxx wrote: > From: Jeff Mahoney <jeffm@xxxxxxxx> > > While running btrfs/011, I hit the following lockdep splat. > > This is the important bit: > pcpu_alloc+0x1ac/0x5e0 > __percpu_counter_init+0x4e/0xb0 > btrfs_init_fs_root+0x99/0x1c0 [btrfs] > btrfs_get_fs_root.part.54+0x5b/0x150 [btrfs] > resolve_indirect_refs+0x130/0x830 [btrfs] > find_parent_nodes+0x69e/0xff0 [btrfs] > btrfs_find_all_roots_safe+0xa0/0x110 [btrfs] > btrfs_find_all_roots+0x50/0x70 [btrfs] > btrfs_qgroup_prepare_account_extents+0x53/0x90 [btrfs] > btrfs_commit_transaction+0x3ce/0x9b0 [btrfs] > > The percpu_counter_init call in btrfs_alloc_subvolume_writers > uses GFP_KERNEL, which we can't do during transaction commit. > > This switches it to GFP_NOFS. > Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx> > --- > fs/btrfs/disk-io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 21f34ad0d411..eb6bb3169a9e 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -1108,7 +1108,7 @@ static struct btrfs_subvolume_writers *btrfs_alloc_subvolume_writers(void) > if (!writers) > return ERR_PTR(-ENOMEM); > > - ret = percpu_counter_init(&writers->counter, 0, GFP_KERNEL); > + ret = percpu_counter_init(&writers->counter, 0, GFP_NOFS); A line above the diff context is another allocation that does GFP_NOFS, so one of the gfp flags were wrong. Looks like there's another instance where percpu allocates with GFP_KERNEL: create_space_info that can be called from the path that allocates chunks, so this also looks like a NOFS candidate. And in the same function, there's another indirect and hidden GFP_KERNEL allocation from kobject_init_and_add. So in this case we can't fix all the gfp problems at the call site and will have to use the scoped approach eventually. I haven't found any instance of such lockdep reports in my logs (over a long period), so it's quite unlikely to end up in the recursive allocation. Patch added to next, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
