On Mon 09-01-17 15:08:27, Vlastimil Babka wrote:
> On 01/06/2017 03:11 PM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@xxxxxxxx>
> >
> > kmem_zalloc_large and _xfs_buf_map_pages use memalloc_noio_{save,restore}
> > API to prevent from reclaim recursion into the fs because vmalloc can
> > invoke unconditional GFP_KERNEL allocations and these functions might be
> > called from the NOFS contexts. The memalloc_noio_save will enforce
> > GFP_NOIO context which is even weaker than GFP_NOFS and that seems to be
> > unnecessary. Let's use memalloc_nofs_{save,restore} instead as it should
> > provide exactly what we need here - implicit GFP_NOFS context.
> >
> > Changes since v1
> > - s@memalloc_noio_restore@memalloc_nofs_restore@ in _xfs_buf_map_pages
> > as per Brian Foster
> >
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
>
> Not a xfs expert, but seems correct.
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Thanks!
>
> Nit below:
>
> > ---
> > fs/xfs/kmem.c | 10 +++++-----
> > fs/xfs/xfs_buf.c | 8 ++++----
> > 2 files changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
> > index a76a05dae96b..d69ed5e76621 100644
> > --- a/fs/xfs/kmem.c
> > +++ b/fs/xfs/kmem.c
> > @@ -65,7 +65,7 @@ kmem_alloc(size_t size, xfs_km_flags_t flags)
> > void *
> > kmem_zalloc_large(size_t size, xfs_km_flags_t flags)
> > {
> > - unsigned noio_flag = 0;
> > + unsigned nofs_flag = 0;
> > void *ptr;
> > gfp_t lflags;
> >
> > @@ -80,14 +80,14 @@ kmem_zalloc_large(size_t size, xfs_km_flags_t flags)
> > * context via PF_MEMALLOC_NOIO to prevent memory reclaim re-entering
> > * the filesystem here and potentially deadlocking.
>
> The comment above is now largely obsolete, or minimally should be
> changed to PF_MEMALLOC_NOFS?
---
diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
index d69ed5e76621..0c9f94f41b6c 100644
--- a/fs/xfs/kmem.c
+++ b/fs/xfs/kmem.c
@@ -77,7 +77,7 @@ kmem_zalloc_large(size_t size, xfs_km_flags_t flags)
* __vmalloc() will allocate data pages and auxillary structures (e.g.
* pagetables) with GFP_KERNEL, yet we may 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 memory reclaim re-entering
+ * context via PF_MEMALLOC_NOFS to prevent memory reclaim re-entering
* the filesystem here and potentially deadlocking.
*/
if (flags & KM_NOFS)
I will fold it into the original patch.
Thanks!
--
Michal Hocko
SUSE Labs
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