On Mon, Apr 15, 2019 at 3:33 PM David Sterba <dsterba@xxxxxxx> wrote:
>
> On Mon, Apr 15, 2019 at 09:29:10AM +0100, fdmanana@xxxxxxxxxx wrote:
> > From: Filipe Manana <fdmanana@xxxxxxxx>
> >
> > As of commit bb739cf08e8f32 ("btrfs: btrfs_check_shared should manage its
> > own transaction") btrfs_check_shared() manages its own transaction, it
> > no longer receives a transaction handle as parameter. Since it is used
> > only in the fiemap path, the ulists it needs to use are allocated before
> > it grabs a transaction handle and we are not holding any locks that could
> > cause a deadlock in case reclaim happens during a memory allocation, we
> > can use the GFP_KERNEL flag to allocate the ulists instead of GFP_NOFS.
> > So do that switch.
> >
> > Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
>
> Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Actually no, this isn't safe, drop it please.
An inode's range is locked, the allocations can trigger writeback for
that inode, and writepages() needs to lock the range as well.
Thanks.
