linux-kernel - [PATCH RFC] f2fs: revalidate empty segment when checkpoint is disabled

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Message-Id: <20241018100150.2852132-1-chao@kernel.org>
Date: Fri, 18 Oct 2024 18:01:50 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Chao Yu <chao@...nel.org>,
	Daniel Rosenberg <drosen@...gle.com>,
	Qi Han <hanqi@...o.com>
Subject: [PATCH RFC] f2fs: revalidate empty segment when checkpoint is disabled

If checkpoint is off, let's set segment as free once all newly
written datas were removed, it fixes below case:

dd if=/dev/zero of=f2fs.img bs=1M count=64
mkfs.f2fs -f f2fs.img
mount -o checkpoint=disable:10% f2fs.img mnt
dd if=/dev/zero of=mnt/file bs=1M count=19
sync
rm mnt/file
dd if=/dev/zero of=mnt/file bs=1M count=9
dd: error writing 'mnt/file': No space left on device

Cc: Daniel Rosenberg <drosen@...gle.com>
Reported-by: Qi Han <hanqi@...o.com>
Signed-off-by: Chao Yu <chao@...nel.org>
---
 fs/f2fs/segment.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e172b3d0aec3..4f480bfc9618 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -849,6 +849,17 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 	valid_blocks = get_valid_blocks(sbi, segno, false);
 	ckpt_valid_blocks = get_ckpt_valid_blocks(sbi, segno, false);
 
+	/*
+	 * If checkpoint is off, let's set segment as free once all newly
+	 * written datas were removed.
+	 */
+	if (is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
+		valid_blocks == 0 && ckpt_valid_blocks == 0) {
+		__remove_dirty_segment(sbi, segno, DIRTY);
+		__set_test_and_free(sbi, segno, false);
+		goto out_lock;
+	}
+
 	if (valid_blocks == 0 && (!is_sbi_flag_set(sbi, SBI_CP_DISABLED) ||
 		ckpt_valid_blocks == usable_blocks)) {
 		__locate_dirty_segment(sbi, segno, PRE);
@@ -859,7 +870,7 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 		/* Recovery routine with SSR needs this */
 		__remove_dirty_segment(sbi, segno, DIRTY);
 	}
-
+out_lock:
 	mutex_unlock(&dirty_i->seglist_lock);
 }
 
-- 
2.40.1