linux-kernel - [PATCH AUTOSEL 5.5 015/542] f2fs: preallocate DIO blocks when forcing buffered

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Date:   Fri, 14 Feb 2020 10:40:07 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>,
        Javier Gonzalez <javier@...igon.com>,
        Damien Le Moal <damien.lemoal@....com>,
        Shin'ichiro Kawasaki <shinichiro.kawasaki@....com>,
        Chao Yu <yuchao0@...wei.com>, Sasha Levin <sashal@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: [PATCH AUTOSEL 5.5 015/542] f2fs: preallocate DIO blocks when forcing buffered_io

From: Jaegeuk Kim <jaegeuk@...nel.org>

[ Upstream commit 47501f87c61ad2aa234add63e1ae231521dbc3f5 ]

The previous preallocation and DIO decision like below.

                         allow_outplace_dio              !allow_outplace_dio
f2fs_force_buffered_io   (*) No_Prealloc / Buffered_IO   Prealloc / Buffered_IO
!f2fs_force_buffered_io  No_Prealloc / DIO               Prealloc / DIO

But, Javier reported Case (*) where zoned device bypassed preallocation but
fell back to buffered writes in f2fs_direct_IO(), resulting in stale data
being read.

In order to fix the issue, actually we need to preallocate blocks whenever
we fall back to buffered IO like this. No change is made in the other cases.

                         allow_outplace_dio              !allow_outplace_dio
f2fs_force_buffered_io   (*) Prealloc / Buffered_IO      Prealloc / Buffered_IO
!f2fs_force_buffered_io  No_Prealloc / DIO               Prealloc / DIO

Reported-and-tested-by: Javier Gonzalez <javier@...igon.com>
Signed-off-by: Damien Le Moal <damien.lemoal@....com>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@....com>
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Reviewed-by: Javier González <javier@...igon.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/f2fs/data.c | 13 -------------
 fs/f2fs/file.c | 43 +++++++++++++++++++++++++++++++++----------
 2 files changed, 33 insertions(+), 23 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index a034cd0ce0217..fc40a72f7827f 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1180,19 +1180,6 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
 	int err = 0;
 	bool direct_io = iocb->ki_flags & IOCB_DIRECT;
 
-	/* convert inline data for Direct I/O*/
-	if (direct_io) {
-		err = f2fs_convert_inline_inode(inode);
-		if (err)
-			return err;
-	}
-
-	if (direct_io && allow_outplace_dio(inode, iocb, from))
-		return 0;
-
-	if (is_inode_flag_set(inode, FI_NO_PREALLOC))
-		return 0;
-
 	map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
 	map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
 	if (map.m_len > map.m_lblk)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 13aef5f28fa8f..33c412d178f0f 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3383,18 +3383,41 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 				ret = -EAGAIN;
 				goto out;
 			}
-		} else {
-			preallocated = true;
-			target_size = iocb->ki_pos + iov_iter_count(from);
+			goto write;
+		}
 
-			err = f2fs_preallocate_blocks(iocb, from);
-			if (err) {
-				clear_inode_flag(inode, FI_NO_PREALLOC);
-				inode_unlock(inode);
-				ret = err;
-				goto out;
-			}
+		if (is_inode_flag_set(inode, FI_NO_PREALLOC))
+			goto write;
+
+		if (iocb->ki_flags & IOCB_DIRECT) {
+			/*
+			 * Convert inline data for Direct I/O before entering
+			 * f2fs_direct_IO().
+			 */
+			err = f2fs_convert_inline_inode(inode);
+			if (err)
+				goto out_err;
+			/*
+			 * If force_buffere_io() is true, we have to allocate
+			 * blocks all the time, since f2fs_direct_IO will fall
+			 * back to buffered IO.
+			 */
+			if (!f2fs_force_buffered_io(inode, iocb, from) &&
+					allow_outplace_dio(inode, iocb, from))
+				goto write;
+		}
+		preallocated = true;
+		target_size = iocb->ki_pos + iov_iter_count(from);
+
+		err = f2fs_preallocate_blocks(iocb, from);
+		if (err) {
+out_err:
+			clear_inode_flag(inode, FI_NO_PREALLOC);
+			inode_unlock(inode);
+			ret = err;
+			goto out;
 		}
+write:
 		ret = __generic_file_write_iter(iocb, from);
 		clear_inode_flag(inode, FI_NO_PREALLOC);
 
-- 
2.20.1