On Mon 06-02-17 07:39:23, Matthew Wilcox wrote: > On Mon, Feb 06, 2017 at 03:07:16PM +0100, Michal Hocko wrote: > > +++ b/fs/xfs/xfs_buf.c > > @@ -442,17 +442,17 @@ _xfs_buf_map_pages( > > bp->b_addr = NULL; > > } else { > > int retried = 0; > > - unsigned noio_flag; > > + unsigned nofs_flag; > > > > /* > > * vm_map_ram() will allocate auxillary structures (e.g. > > * pagetables) with GFP_KERNEL, yet we are likely to be under > > * GFP_NOFS context here. Hence we need to tell memory reclaim > > - * that we are in such a context via PF_MEMALLOC_NOIO to prevent > > + * that we are in such a context via PF_MEMALLOC_NOFS to prevent > > * memory reclaim re-entering the filesystem here and > > * potentially deadlocking. > > */ > > This comment feels out of date ... how about: which part is out of date? > > /* > * vm_map_ram will allocate auxiliary structures (eg page > * tables) with GFP_KERNEL. If that tries to reclaim memory > * by calling back into this filesystem, we may deadlock. > * Prevent that by setting the NOFS flag. > */ dunno, the previous wording seems clear enough to me. Maybe little bit more chatty than yours but I am not sure this is worth changing. > > > - noio_flag = memalloc_noio_save(); > > + nofs_flag = memalloc_nofs_save(); > > do { > > bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count, > > -1, PAGE_KERNEL); > > Also, I think it shows that this is the wrong place in XFS to be calling > memalloc_nofs_save(). I'm not arguing against including this patch; > it's a step towards where we want to be. I also don't know XFS well > enough to know where to set that flag ;-) Presumably when we start a > transaction ... ? Yes that is what I would like to achieve longterm. And the reason why I didn't want to mimic this pattern in kvmalloc as some have suggested. It just takes much more time to get there from the past experience and we should really start somewhere. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>