linux-kernel - Re: [PATCH] f2fs: Fix direct IO handling

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Date:   Tue, 26 Nov 2019 15:44:28 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Damien Le Moal <damien.lemoal@....com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>,
        linux-fsdevel@...r.kernel.org,
        Javier Gonzalez <javier@...igon.com>,
        Shinichiro Kawasaki <shinichiro.kawasaki@....com>
Subject: Re: [PATCH] f2fs: Fix direct IO handling

On 11/26, Damien Le Moal wrote:
> f2fs_preallocate_blocks() identifies direct IOs using the IOCB_DIRECT
> flag for a kiocb structure. However, the file system direct IO handler
> function f2fs_direct_IO() may have decided that a direct IO has to be
> exececuted as a buffered IO using the function f2fs_force_buffered_io().
> This is the case for instance for volumes including zoned block device
> and for unaligned write IOs with LFS mode enabled.
> 
> These 2 different methods of identifying direct IOs can result in
> inconsistencies generating stale data access for direct reads after a
> direct IO write that is treated as a buffered write. Fix this
> inconsistency by combining the IOCB_DIRECT flag test with the result
> of f2fs_force_buffered_io().
> 
> Reported-by: Javier Gonzalez <javier@...igon.com>
> Signed-off-by: Damien Le Moal <damien.lemoal@....com>
> ---
>  fs/f2fs/data.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5755e897a5f0..8ac2d3b70022 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  	int flag;
>  	int err = 0;
>  	bool direct_io = iocb->ki_flags & IOCB_DIRECT;
> +	bool do_direct_io = direct_io &&
> +		!f2fs_force_buffered_io(inode, iocb, from);
>  
>  	/* convert inline data for Direct I/O*/
>  	if (direct_io) {
> @@ -1081,7 +1083,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  			return err;
>  	}
>  
> -	if (direct_io && allow_outplace_dio(inode, iocb, from))
> +	if (do_direct_io && allow_outplace_dio(inode, iocb, from))

It seems f2fs_force_buffered_io() includes allow_outplace_dio().

How about this?
---
 fs/f2fs/data.c | 13 -------------
 fs/f2fs/file.c | 35 +++++++++++++++++++++++++----------
 2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index a034cd0ce021..fc40a72f7827 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 c0560d62dbee..6b32ac6c3382 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3386,18 +3386,33 @@ 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*/
+			err = f2fs_convert_inline_inode(inode);
+			if (err)
+				goto out_err;
+
+			if (!f2fs_force_buffered_io(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);
 
-- 
2.19.0.605.g01d371f741-goog