Re: [PATCH] swapin flush cache bug

[NIIBE Yutaka]

Hello Marcelo, 

This is follow-up to the mail in February.  You may perhaps forget the
context, it's the bug of MM about cache flushing for swapped-in-pages.
I see this bug on SuperH port (SH-4).

I think that we have this issue on the machine whose flush_dcache_page()
is defined.  In current code, the cache aren't flushed for 
the asynchronously-swapped-in pages which is cached in swap cache.
This is the problem.

Marcelo Tosatti writes:
 > Yet another thing (1) on end_buffer_io_async() to handle a case which is
 > only true for a specific user of it. Since the other special case handling
 > is for swap IO too, I think a separate IO end operation for swap would be
 > interesting.
 > 
 > (1) The current one is SetPageDecrAfter handling.

How about this?  I've updated MM bugzilla already.

2001-06-26  NIIBE Yutaka  <[e-mail]>

	* include/linux/mm.h (PG_flush_after, PageFlushAfter,
	SetPageFlushAfter, PageTestandClearFlushAfter): New bit.
	* mm/page_io.c (rw_swap_page_base): Set flush-after bit.
	* fs/buffer.c (end_buffer_io_async): Implement flush-ing
	with PG_flush_after.

	* mm/memory.c (do_swap_page): Remove flush-ing the page.

diff -ruNp --exclude=CVS --exclude=.cvsignore v2.4.6-pre5/fs/buffer.c kernel/fs/buffer.c
--- v2.4.6-pre5/fs/buffer.c	Mon Jun 25 18:48:07 2001
+++ kernel/fs/buffer.c	Tue Jun 26 15:11:17 2001
@@ -831,6 +831,9 @@ static void end_buffer_io_async(struct b
 	if (PageTestandClearDecrAfter(page))
 		atomic_dec(&nr_async_pages);
 
+	if (PageTestandClearFlushAfter(page))
+		flush_dcache_page(page);
+
 	UnlockPage(page);
 
 	return;
diff -ruNp --exclude=CVS --exclude=.cvsignore v2.4.6-pre5/include/linux/mm.h kernel/include/linux/mm.h
--- v2.4.6-pre5/include/linux/mm.h	Mon Jun 25 18:48:09 2001
+++ kernel/include/linux/mm.h	Tue Jun 26 14:58:56 2001
@@ -282,6 +282,7 @@ typedef struct page {
 #define PG_inactive_clean	11
 #define PG_highmem		12
 #define PG_checked		13	/* kill me in 2.5.<early>. */
+#define PG_flush_after		14
 				/* bits 21-29 unused */
 #define PG_arch_1		30
 #define PG_reserved		31
@@ -364,6 +365,10 @@ static inline void set_page_dirty(struct
 
 #define SetPageReserved(page)		set_bit(PG_reserved, &(page)->flags)
 #define ClearPageReserved(page)		clear_bit(PG_reserved, &(page)->flags)
+
+#define PageFlushAfter(page)	test_bit(PG_flush_after, &(page)->flags)
+#define SetPageFlushAfter(page)	set_bit(PG_flush_after, &(page)->flags)
+#define PageTestandClearFlushAfter(page)	test_and_clear_bit(PG_flush_after, &(page)->flags)
 
 /*
  * Error return values for the *_nopage functions
diff -ruNp --exclude=CVS --exclude=.cvsignore v2.4.6-pre5/mm/memory.c kernel/mm/memory.c
--- v2.4.6-pre5/mm/memory.c	Mon Jun 25 18:48:10 2001
+++ kernel/mm/memory.c	Tue Jun 26 14:48:15 2001
@@ -1109,8 +1109,6 @@ static int do_swap_page(struct mm_struct
 			return -1;
 		}
 		wait_on_page(page);
-		flush_page_to_ram(page);
-		flush_icache_page(vma, page);
 	}
 
 	/*
diff -ruNp --exclude=CVS --exclude=.cvsignore v2.4.6-pre5/mm/page_io.c kernel/mm/page_io.c
--- v2.4.6-pre5/mm/page_io.c	Mon Apr 30 16:15:32 2001
+++ kernel/mm/page_io.c	Tue Jun 26 15:01:00 2001
@@ -50,6 +50,7 @@ static int rw_swap_page_base(int rw, swp
 
 	if (rw == READ) {
 		ClearPageUptodate(page);
+		SetPageFlushAfter(page);
 		kstat.pswpin++;
 	} else
 		kstat.pswpout++;
--