linux-kernel - [PATCH] f2fs: fix missing discard for active segments

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Message-Id: <20241203065108.2763436-1-guochunhai@vivo.com>
Date: Mon,  2 Dec 2024 23:51:08 -0700
From: Chunhai Guo <guochunhai@...o.com>
To: chao@...nel.org,
	jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Chunhai Guo <guochunhai@...o.com>
Subject: [PATCH] f2fs: fix missing discard for active segments

locate_dirty_segment() does not set any current active segment as a
prefree segment. Thus, the issue described below may occur:

Step 1: During a checkpoint, add_discard_addrs() does not handle the
current active 'segment X' with 0 valid blocks (and non-zero discard
blocks). As a result, no struct discard_cmd is created for 'segment X'
and the value of sbi->discard_blks cannot be reduced to 0 after the
checkpoint.

Step 2: f2fs is umounted without setting CP_TRIMMED_FLAG, as
sbi->discard_blks is non-zero.

Since add_discard_addrs() can handle active segments with non-zero valid
blocks, it is reasonable to fix this issue by also handling active
segments with 0 valid blocks in add_discard_addrs().

Signed-off-by: Chunhai Guo <guochunhai@...o.com>
---
 fs/f2fs/segment.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index eade36c5ef13..4fb1dc4aab97 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2090,7 +2090,9 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
 		return false;

 	if (!force) {
-		if (!f2fs_realtime_discard_enable(sbi) || !se->valid_blocks ||
+		if (!f2fs_realtime_discard_enable(sbi) ||
+			(!se->valid_blocks &&
+				!IS_CURSEG(sbi, cpc->trim_start)) ||
 			SM_I(sbi)->dcc_info->nr_discards >=
 				SM_I(sbi)->dcc_info->max_discards)
 			return false;
-- 
2.34.1