linux-kernel - [PATCH] f2fs: disble physical prealloc in LSF mount

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Message-Id: <20191122085952.12754-1-javier@javigon.com>
Date:   Fri, 22 Nov 2019 09:59:52 +0100
From:   Javier González <javier@...igon.com>
To:     jaegeuk@...nel.org, yuchao0@...wei.com
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, damien.lemoal@....com,
        Javier González <javier.gonz@...sung.com>
Subject: [PATCH] f2fs: disble physical prealloc in LSF mount

From: Javier González <javier.gonz@...sung.com>

Fix file system corruption when using LFS mount (e.g., in zoned
devices). Seems like the fallback into buffered I/O creates an
inconsistency if the application is assuming both read and write DIO. I
can easily reproduce a corruption with a simple RocksDB test.

Might be that the f2fs_forced_buffered_io path brings some problems too,
but I have not seen other failures besides this one.

Problem reproducible without a zoned block device, simply by forcing
LFS mount:

  $ sudo mkfs.f2fs -f -m /dev/nvme0n1
  $ sudo mount /dev/nvme0n1 /mnt/f2fs
  $ sudo  /opt/rocksdb/db_bench  --benchmarks=fillseq --use_existing_db=0
  --use_direct_reads=true --use_direct_io_for_flush_and_compaction=true
  --db=/mnt/f2fs --num=5000 --value_size=1048576 --verify_checksum=1
  --block_size=65536

Note that the options that cause the problem are:
  --use_direct_reads=true --use_direct_io_for_flush_and_compaction=true

Fixes: f9d6d0597698 ("f2fs: fix out-place-update DIO write")

Signed-off-by: Javier González <javier.gonz@...sung.com>
---
 fs/f2fs/data.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5755e897a5f0..b045dd6ab632 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1081,9 +1081,6 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
 			return err;
 	}
 
-	if (direct_io && allow_outplace_dio(inode, iocb, from))
-		return 0;
-
 	if (is_inode_flag_set(inode, FI_NO_PREALLOC))
 		return 0;
 
-- 
2.17.1