From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
linux-xfs@vger.kernel.org, dm-devel@redhat.com,
Mikulas Patocka <mpatocka@redhat.com>,
Jens Axboe <axboe@kernel.dk>, NeilBrown <neilb@suse.de>
Subject: [PATCH 2/6] mm: Add become_kswapd and restore_kswapd
Date: Thu, 25 Jun 2020 12:31:18 +0100 [thread overview]
Message-ID: <20200625113122.7540-3-willy@infradead.org> (raw)
In-Reply-To: <20200625113122.7540-1-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.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/xfs/libxfs/xfs_btree.c | 14 ++++++++------
include/linux/sched/mm.h | 26 ++++++++++++++++++++++++++
mm/vmscan.c | 16 +---------------
3 files changed, 35 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 1a7e1ab1be85..b0089eadc367 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -308,6 +308,32 @@ static inline void memalloc_nocma_restore(unsigned int flags)
}
#endif
+/*
+ * 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).
+ */
+#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);
+}
+
static inline void set_current_io_flusher(void)
{
current->flags |= PF_LOCAL_THROTTLE;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b6d84326bdf2..27ae76699899 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3870,19 +3870,7 @@ 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);
@@ -3932,8 +3920,6 @@ static int kswapd(void *p)
goto kswapd_try_sleep;
}
- tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
-
return 0;
}
--
2.27.0
next prev parent reply other threads:[~2020-06-25 11:32 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 11:31 [PATCH 0/6] Overhaul memalloc_no* Matthew Wilcox (Oracle)
2020-06-25 11:31 ` [PATCH 1/6] mm: Replace PF_MEMALLOC_NOIO with memalloc_noio Matthew Wilcox (Oracle)
2020-06-25 12:22 ` Michal Hocko
2020-06-25 12:34 ` Matthew Wilcox
2020-06-25 12:42 ` Michal Hocko
2020-06-25 11:31 ` Matthew Wilcox (Oracle) [this message]
2020-06-25 12:31 ` [PATCH 2/6] mm: Add become_kswapd and restore_kswapd Michal Hocko
2020-06-25 11:31 ` [PATCH 3/6] xfs: Convert to memalloc_nofs_save Matthew Wilcox (Oracle)
2020-06-25 11:31 ` [PATCH 4/6] mm: Replace PF_MEMALLOC_NOFS with memalloc_nofs Matthew Wilcox (Oracle)
2020-06-25 13:35 ` Michal Hocko
2020-06-25 11:31 ` [PATCH 5/6] mm: Replace PF_MEMALLOC_NOIO with memalloc_nocma Matthew Wilcox (Oracle)
2020-06-25 11:31 ` [PATCH 6/6] mm: Add memalloc_nowait Matthew Wilcox (Oracle)
2020-06-25 12:40 ` Michal Hocko
2020-06-25 13:10 ` Matthew Wilcox
2020-06-25 13:34 ` Michal Hocko
2020-06-25 19:05 ` kernel test robot
2020-06-25 23:51 ` kernel test robot
2020-06-29 5:08 ` Mike Rapoport
2020-06-29 12:18 ` Matthew Wilcox
2020-06-29 12:52 ` Michal Hocko
2020-06-29 13:45 ` Mike Rapoport
2020-06-29 21:28 ` Matthew Wilcox
2020-06-30 6:34 ` Michal Hocko
2020-07-01 4:12 ` Matthew Wilcox
2020-07-01 5:53 ` Michal Hocko
2020-07-01 7:04 ` Mike Rapoport
2020-09-24 0:39 ` Mike Snitzer
2020-09-24 1:10 ` Matthew Wilcox
2020-10-23 14:49 ` Daniel Vetter
2020-06-25 18:48 ` [PATCH 0/6] Overhaul memalloc_no* Darrick J. Wong
2020-06-25 20:34 ` Matthew Wilcox
2020-06-25 20:36 ` Michal Hocko
2020-06-25 20:40 ` Matthew Wilcox
2020-06-26 15:02 ` Mikulas Patocka
2020-06-26 23:08 ` Dave Chinner
2020-06-27 13:09 ` Mikulas Patocka
2020-06-29 0:35 ` Dave Chinner
2020-06-29 13:43 ` Mikulas Patocka
2020-06-29 22:34 ` Dave Chinner
2020-07-03 14:26 ` [PATCH] dm-bufio: do cleanup from a workqueue Mikulas Patocka
2020-06-29 8:22 ` [PATCH 0/6] Overhaul memalloc_no* Michal Hocko
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