From: Yafang Shao <laoar.shao@gmail.com>
To: darrick.wong@oracle.com, willy@infradead.org,
david@fromorbit.com, hch@infradead.org, mhocko@kernel.org,
akpm@linux-foundation.org, dhowells@redhat.com,
jlayton@redhat.com
Cc: linux-fsdevel@vger.kernel.org, linux-cachefs@redhat.com,
linux-xfs@vger.kernel.org, linux-mm@kvack.org,
Michal Hocko <mhocko@suse.com>, Christoph Hellwig <hch@lst.de>,
Yafang Shao <laoar.shao@gmail.com>
Subject: [PATCH v11 1/4] mm: Add become_kswapd and restore_kswapd
Date: Tue, 8 Dec 2020 20:28:21 +0800 [thread overview]
Message-ID: <20201208122824.16118-2-laoar.shao@gmail.com> (raw)
In-Reply-To: <20201208122824.16118-1-laoar.shao@gmail.com>
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Since XFS needs to pretend to be kswapd in some of its worker threads,
create methods to save & restore kswapd state. Don't bother restoring
kswapd state in kswapd -- the only time we reach this code is when we're
exiting and the task_struct is about to be destroyed anyway.
Cc: Dave Chinner <david@fromorbit.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
fs/xfs/libxfs/xfs_btree.c | 14 ++++++++------
include/linux/sched/mm.h | 23 +++++++++++++++++++++++
mm/vmscan.c | 16 +---------------
3 files changed, 32 insertions(+), 21 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 2d25bab68764..a04a44238aab 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -2813,8 +2813,9 @@ xfs_btree_split_worker(
{
struct xfs_btree_split_args *args = container_of(work,
struct xfs_btree_split_args, work);
+ bool is_kswapd = args->kswapd;
unsigned long pflags;
- unsigned long new_pflags = PF_MEMALLOC_NOFS;
+ int memalloc_nofs;
/*
* we are in a transaction context here, but may also be doing work
@@ -2822,16 +2823,17 @@ xfs_btree_split_worker(
* temporarily to ensure that we don't block waiting for memory reclaim
* in any way.
*/
- if (args->kswapd)
- new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
-
- current_set_flags_nested(&pflags, new_pflags);
+ if (is_kswapd)
+ pflags = become_kswapd();
+ memalloc_nofs = memalloc_nofs_save();
args->result = __xfs_btree_split(args->cur, args->level, args->ptrp,
args->key, args->curp, args->stat);
complete(args->done);
- current_restore_flags_nested(&pflags, new_pflags);
+ memalloc_nofs_restore(memalloc_nofs);
+ if (is_kswapd)
+ restore_kswapd(pflags);
}
/*
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index d5ece7a9a403..2faf03e79a1e 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -278,6 +278,29 @@ static inline void memalloc_nocma_restore(unsigned int flags)
}
#endif
+/*
+ * Tell the memory management code that this thread is working on behalf
+ * of background memory reclaim (like kswapd). That means that it will
+ * get access to memory reserves should it need to allocate memory in
+ * order to make forward progress. With this great power comes great
+ * responsibility to not exhaust those reserves.
+ */
+#define KSWAPD_PF_FLAGS (PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD)
+
+static inline unsigned long become_kswapd(void)
+{
+ unsigned long flags = current->flags & KSWAPD_PF_FLAGS;
+
+ current->flags |= KSWAPD_PF_FLAGS;
+
+ return flags;
+}
+
+static inline void restore_kswapd(unsigned long flags)
+{
+ current->flags &= ~(flags ^ KSWAPD_PF_FLAGS);
+}
+
#ifdef CONFIG_MEMCG
DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
/**
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1b8f0e059767..77bc1dda75bf 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3869,19 +3869,7 @@ static int kswapd(void *p)
if (!cpumask_empty(cpumask))
set_cpus_allowed_ptr(tsk, cpumask);
- /*
- * Tell the memory management that we're a "memory allocator",
- * and that if we need more memory we should get access to it
- * regardless (see "__alloc_pages()"). "kswapd" should
- * never get caught in the normal page freeing logic.
- *
- * (Kswapd normally doesn't need memory anyway, but sometimes
- * you need a small amount of memory in order to be able to
- * page out something else, and this flag essentially protects
- * us from recursively trying to free more memory as we're
- * trying to free the first piece of memory in the first place).
- */
- tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ become_kswapd();
set_freezable();
WRITE_ONCE(pgdat->kswapd_order, 0);
@@ -3931,8 +3919,6 @@ static int kswapd(void *p)
goto kswapd_try_sleep;
}
- tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
-
return 0;
}
--
2.18.4
next prev parent reply other threads:[~2020-12-08 12:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-08 12:28 [PATCH v11 0/4] xfs: avoid transaction reservation recursion Yafang Shao
2020-12-08 12:28 ` Yafang Shao [this message]
2020-12-08 12:28 ` [PATCH v11 2/4] xfs: use memalloc_nofs_{save,restore} in xfs transaction Yafang Shao
2020-12-08 19:02 ` Darrick J. Wong
2020-12-08 12:28 ` [PATCH v11 3/4] xfs: refactor the usage around xfs_trans_context_{set,clear} Yafang Shao
2020-12-08 18:59 ` Darrick J. Wong
[not found] ` <CALOAHbB1uKmQ7ns08KW4zH1ikqD0GAY_Y7VySzmTY0=LTEPURA@mail.gmail.com>
2020-12-09 3:53 ` Darrick J. Wong
2020-12-09 10:43 ` Yafang Shao
2020-12-08 12:28 ` [PATCH v11 4/4] xfs: use current->journal_info to avoid transaction reservation recursion Yafang Shao
2020-12-08 18:59 ` Darrick J. Wong
2020-12-09 1:40 ` Yafang Shao
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