Re: [PATCH 0/6] Overhaul memalloc_no*

Darrick J. Wong
2020-06-25T18:51:42Z

On Thu, Jun 25, 2020 at 12:31:16PM +0100, 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.

So, uh, how does this intersect with the patch "xfs: reintroduce
PF_FSTRANS for transaction reservation recursion protection" that
re-adds PF_TRANS because uh I guess we lost some subtlety or another at
some point?

I don't have any strong opinion on this series one way or another, but
seeing as that patch was generating discussion about how PF_MEMALLOC_NO*
is not quite the same as PF_TRANS, I kinda want all these competing PF
tweaks and reworks to come together into a single series to review,
rather than the four(?) different people submitting conflicting changes.

[adding Yafang Shao to cc]

--D

> 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
>