Re: [PATCH 0/6] Overhaul memalloc_no*

Mikulas Patocka
2020-06-26T15:04:00Z

Hi

I suggest to join memalloc_noio and memalloc_nofs into just one flag that
prevents both filesystem recursion and i/o recursion.

Note that any I/O can recurse into a filesystem via the loop device, thus
it doesn't make much sense to have a context where PF_MEMALLOC_NOFS is set
and PF_MEMALLOC_NOIO is not set.

Mikulas

On Thu, 25 Jun 2020, Matthew Wilcox (Oracle) wrote:

> I want a memalloc_nowait like we have memalloc_noio and memalloc_nofs
> for an upcoming patch series, and Jens also wants it for non-blocking
> io_uring. It turns out we already have dm-bufio which could benefit
> from memalloc_nowait, so it may as well go into the tree now.
>
> The biggest problem is that we're basically out of PF_ flags, so we need
> to find somewhere else to store the PF_MEMALLOC_NOWAIT flag. It turns
> out the PF_ flags are really supposed to be used for flags which are
> accessed from other tasks, and the MEMALLOC flags are only going to
> be used by this task. So shuffling everything around frees up some PF
> flags and generally makes the world a better place.
>
> Patch series also available from
> http://git.infradead.org/users/willy/linux.git/shortlog/refs/heads/memalloc
>
> Matthew Wilcox (Oracle) (6):
> mm: Replace PF_MEMALLOC_NOIO with memalloc_noio
> mm: Add become_kswapd and restore_kswapd
> xfs: Convert to memalloc_nofs_save
> mm: Replace PF_MEMALLOC_NOFS with memalloc_nofs
> mm: Replace PF_MEMALLOC_NOIO with memalloc_nocma
> mm: Add memalloc_nowait
>
> drivers/block/loop.c | 3 +-
> drivers/md/dm-bufio.c | 30 ++++--------
> drivers/md/dm-zoned-metadata.c | 5 +-
> fs/iomap/buffered-io.c | 2 +-
> fs/xfs/kmem.c | 2 +-
> fs/xfs/libxfs/xfs_btree.c | 14 +++---
> fs/xfs/xfs_aops.c | 4 +-
> fs/xfs/xfs_buf.c | 2 +-
> fs/xfs/xfs_linux.h | 6 ---
> fs/xfs/xfs_trans.c | 14 +++---
> fs/xfs/xfs_trans.h | 2 +-
> include/linux/sched.h | 7 +--
> include/linux/sched/mm.h | 84 ++++++++++++++++++++++++++--------
> kernel/sys.c | 8 ++--
> mm/vmscan.c | 16 +------
> 15 files changed, 105 insertions(+), 94 deletions(-)
>
> --
> 2.27.0
>