From: Christoph Lameter <clameter@sgi.com>
Date: Sun, 8 Jan 2006 09:00:47 +0000 (-0800)
Subject: [PATCH] Swap Migration V5: PF_SWAPWRITE to allow writing to swap
X-Git-Tag: firefly_0821_release~39630
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=930d915252edda7042c944ed3c30194a2f9fe163;p=firefly-linux-kernel-4.4.55.git

[PATCH] Swap Migration V5: PF_SWAPWRITE to allow writing to swap

Add PF_SWAPWRITE to control a processes permission to write to swap.

- Use PF_SWAPWRITE in may_write_to_queue() instead of checking for kswapd
  and pdflush

- Set PF_SWAPWRITE flag for kswapd and pdflush

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7da33619d5d0..a74662077d60 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -895,6 +895,7 @@ do { if (atomic_dec_and_test(&(tsk)->usage)) __put_task_struct(tsk); } while(0)
 #define PF_SYNCWRITE	0x00200000	/* I am doing a sync write */
 #define PF_BORROWED_MM	0x00400000	/* I am a kthread doing use_mm */
 #define PF_RANDOMIZE	0x00800000	/* randomize virtual address space */
+#define PF_SWAPWRITE	0x01000000	/* Allowed to write to swap */
 
 /*
  * Only the _current_ task can read/write to tsk->flags, but other
diff --git a/mm/pdflush.c b/mm/pdflush.c
index 52822c98c489..c4b6d0afd736 100644
--- a/mm/pdflush.c
+++ b/mm/pdflush.c
@@ -90,7 +90,7 @@ struct pdflush_work {
 
 static int __pdflush(struct pdflush_work *my_work)
 {
-	current->flags |= PF_FLUSHER;
+	current->flags |= PF_FLUSHER | PF_SWAPWRITE;
 	my_work->fn = NULL;
 	my_work->who = current;
 	INIT_LIST_HEAD(&my_work->list);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 261a56ee11b6..6c30a8c59795 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -268,9 +268,7 @@ static inline int is_page_cache_freeable(struct page *page)
 
 static int may_write_to_queue(struct backing_dev_info *bdi)
 {
-	if (current_is_kswapd())
-		return 1;
-	if (current_is_pdflush())	/* This is unlikely, but why not... */
+	if (current->flags & PF_SWAPWRITE)
 		return 1;
 	if (!bdi_write_congested(bdi))
 		return 1;
@@ -1299,7 +1297,7 @@ static int kswapd(void *p)
 	 * 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_KSWAPD;
+	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
 
 	order = 0;
 	for ( ; ; ) {