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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 6/6] mm: Add memalloc_nowait
Date: Thu, 25 Jun 2020 12:31:22 +0100
Message-ID: <20200625113122.7540-7-willy@infradead.org> (raw)
In-Reply-To: <20200625113122.7540-1-willy@infradead.org>

Similar to memalloc_noio() and memalloc_nofs(), memalloc_nowait()
guarantees we will not sleep to reclaim memory.  Use it to simplify
dm-bufio's allocations.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 drivers/md/dm-bufio.c    | 30 ++++++++----------------------
 include/linux/sched.h    |  1 +
 include/linux/sched/mm.h | 12 ++++++++----
 3 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 6d1565021d74..140ada9a2c8f 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -412,23 +412,6 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 
 	*data_mode = DATA_MODE_VMALLOC;
 
-	/*
-	 * __vmalloc allocates the data pages and auxiliary structures with
-	 * gfp_flags that were specified, but pagetables are always allocated
-	 * with GFP_KERNEL, no matter what was specified as gfp_mask.
-	 *
-	 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
-	 * all allocations done by this process (including pagetables) are done
-	 * as if GFP_NOIO was specified.
-	 */
-	if (gfp_mask & __GFP_NORETRY) {
-		unsigned noio_flag = memalloc_noio_save();
-		void *ptr = __vmalloc(c->block_size, gfp_mask);
-
-		memalloc_noio_restore(noio_flag);
-		return ptr;
-	}
-
 	return __vmalloc(c->block_size, gfp_mask);
 }
 
@@ -866,9 +849,6 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
 	 * dm-bufio is resistant to allocation failures (it just keeps
 	 * one buffer reserved in cases all the allocations fail).
 	 * So set flags to not try too hard:
-	 *	GFP_NOWAIT: don't wait; if we need to sleep we'll release our
-	 *		    mutex and wait ourselves.
-	 *	__GFP_NORETRY: don't retry and rather return failure
 	 *	__GFP_NOMEMALLOC: don't use emergency reserves
 	 *	__GFP_NOWARN: don't print a warning in case of failure
 	 *
@@ -877,7 +857,9 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
 	 */
 	while (1) {
 		if (dm_bufio_cache_size_latch != 1) {
-			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+			unsigned nowait_flag = memalloc_nowait_save();
+			b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN);
+			memalloc_nowait_restore(nowait_flag);
 			if (b)
 				return b;
 		}
@@ -886,8 +868,12 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
 			return NULL;
 
 		if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
+			unsigned noio_flag;
+
 			dm_bufio_unlock(c);
-			b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+			noio_flag = memalloc_noio_save();
+			b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN);
+			memalloc_noio_restore(noio_flag);
 			dm_bufio_lock(c);
 			if (b)
 				return b;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 90336850e940..b1c2cddd366c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -803,6 +803,7 @@ struct task_struct {
 #endif
 	unsigned			memalloc_noio:1;
 	unsigned			memalloc_nofs:1;
+	unsigned			memalloc_nowait:1;
 	unsigned			memalloc_nocma:1;
 
 	unsigned long			atomic_flags; /* Flags requiring atomic access. */
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 6f7b59a848a6..6484569f50df 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -179,12 +179,16 @@ static inline bool in_vfork(struct task_struct *tsk)
 static inline gfp_t current_gfp_context(gfp_t flags)
 {
 	if (unlikely(current->memalloc_noio || current->memalloc_nofs ||
-		     current->memalloc_nocma)) {
+		     current->memalloc_nocma) || current->memalloc_nowait) {
 		/*
-		 * NOIO implies both NOIO and NOFS and it is a weaker context
-		 * so always make sure it makes precedence
+		 * Clearing DIRECT_RECLAIM means we won't get to the point
+		 * of testing IO or FS, so we don't need to bother clearing
+		 * them.  noio implies neither IO nor FS and it is a weaker
+		 * context so always make sure it takes precedence.
 		 */
-		if (current->memalloc_noio)
+		if (current->memalloc_nowait)
+			flags &= ~__GFP_DIRECT_RECLAIM;
+		else if (current->memalloc_noio)
 			flags &= ~(__GFP_IO | __GFP_FS);
 		else if (current->memalloc_nofs)
 			flags &= ~__GFP_FS;
-- 
2.27.0



  parent reply index

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 ` [PATCH 2/6] mm: Add become_kswapd and restore_kswapd Matthew Wilcox (Oracle)
2020-06-25 12:31   ` 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 ` Matthew Wilcox (Oracle) [this message]
2020-06-25 12:40   ` [PATCH 6/6] mm: Add memalloc_nowait 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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