linux-kernel - [PATCH v2] f2fs: avoid unused block when dio write in LFS mode

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Message-ID: <20240905052433epcms2p1dac78dff43776cc158bac5ae9d118160@epcms2p1>
Date: Thu, 05 Sep 2024 14:24:33 +0900
From: Daejun Park <daejun7.park@...sung.com>
To: Chao Yu <chao@...nel.org>, "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
	"linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: Seokhwan Kim <sukka.kim@...sung.com>, Dongjin Kim
	<dongjin_.kim@...sung.com>, Yonggil Song <yonggil.song@...sung.com>, Jaeyoon
	Choi <j_yoon.choi@...sung.com>, Nayeon Kim <nayeoni.kim@...sung.com>, Siwoo
	Jung <siu.jung@...sung.com>, Daejun Park <daejun7.park@...sung.com>
Subject: [PATCH v2] f2fs: avoid unused block when dio write in LFS mode

This patch addresses the problem that when using LFS mode, unused blocks
may occur in f2fs_map_blocks() during block allocation for dio writes.

If a new section is allocated during block allocation, it will not be
included in the map struct by map_is_mergeable() if the LBA of the
allocated block is not contiguous. However, the block already allocated
in this process will remain unused due to the LFS mode.

This patch avoids the possibility of unused blocks by escaping
f2fs_map_blocks() when allocating the last block in a section.

Signed-off-by: Daejun Park <daejun7.park@...sung.com>
---

v2: Applied segment check code suggested by Chao Yu.


 fs/f2fs/data.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index c6d688208f8b..b94cf6eea2f9 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1712,6 +1712,14 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
 		dn.ofs_in_node = end_offset;
 	}
 
+	if (flag == F2FS_GET_BLOCK_DIO && f2fs_lfs_mode(sbi) &&
+	    map->m_may_create) {
+		/* the next block to be allocated may not be contiguous. */
+		if (GET_SEGOFF_FROM_SEG0(sbi, blkaddr) % BLKS_PER_SEC(sbi) ==
+		    CAP_BLKS_PER_SEC(sbi) - 1)
+			goto sync_out;
+	}
+
 	if (pgofs >= end)
 		goto sync_out;
 	else if (dn.ofs_in_node < end_offset)
-- 
2.25.1