linux-kernel - Re: [PATCH v2] f2fs: clear cold data flag if IO is not counted

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Message-ID: <20181017023404.GB77619@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Tue, 16 Oct 2018 19:34:04 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v2] f2fs: clear cold data flag if IO is not counted

This reverts commit 66110abc4c931f879d70e83e1281f891699364bf.

If we clear the cold data flag out of the writeback flow, we can miscount
-1 by end_io.

Balancing F2FS Async:
 - IO (CP:    1, Data:   -1, Flush: (   0    0    1), Discard: (   ...

GC thread:                              IRQ
- move_data_page()
 - set_page_dirty()
  - clear_cold_data()
                                        - f2fs_write_end_io()
                                         - type = WB_DATA_TYPE(page);
                                           here, we get wrong type
                                         - dec_page_count(sbi, type);
 - f2fs_wait_on_page_writeback()

Cc: <stable@...r.kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/data.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 3f272c18fb61..0d0b4dd55b04 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2650,10 +2650,6 @@ static int f2fs_set_data_page_dirty(struct page *page)
 	if (!PageUptodate(page))
 		SetPageUptodate(page);
 
-	/* don't remain PG_checked flag which was set during GC */
-	if (is_cold_data(page))
-		clear_cold_data(page);
-
 	if (f2fs_is_atomic_file(inode) && !f2fs_is_commit_atomic_write(inode)) {
 		if (!IS_ATOMIC_WRITTEN_PAGE(page)) {
 			f2fs_register_inmem_page(inode, page);
-- 
2.19.0.605.g01d371f741-goog