On Sat, Mar 25, 2017 at 09:48:28AM +0300, Denis Kirjanov wrote: > On 3/25/17, Jeff Mahoney <je...@suse.com> wrote: > > On 3/24/17 5:02 AM, Denis Kirjanov wrote: > >> Hi guys, > >> > >> Looks like that current code does GFP_KERNEL allocation inside > >> __link_block_group. > >> the function invokes kobject_add and internally creates sysfs files > >> with the GFP_KERNEL flag set. > > > > Yep, that's a bug. > > > >> But since do_chunk_alloc executes insides the btrfs transaction it's > >> not allowed to sleep. > > > > It's allowed to sleep but isn't allowed to do reclaim that involves file > > system writeback. Michal Hocko's allocation context idea would fix > > this, but it's not there yet, so we'll need to defer the kobject_add > > until we can use GFP_KERNEL. > > Ok, I see. Can you point out to the initial patchset?
https://lwn.net/Articles/716323/ Fixing this properly is a lot of work so we might need to add a temporary workaround, as Jeff suggests, to move calling into sysfs to a later time.
