linux-kernel - Re: [PATCH v2] f2fs: Fix direct IO handling

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Message-ID: <20191204081642.gnd55byogedrhfoz@MacBook-Pro.gnusmas>
Date:   Wed, 4 Dec 2019 09:16:42 +0100
From:   Javier Gonzalez <javier@...igon.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Damien Le Moal <damien.lemoal@....com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>,
        linux-fsdevel@...r.kernel.org,
        Shinichiro Kawasaki <shinichiro.kawasaki@....com>
Subject: Re: [PATCH v2] f2fs: Fix direct IO handling

On 03.12.2019 09:33, Jaegeuk Kim wrote:
>Thank you for checking the patch.
>I found some regressions in xfstests, so want to follow the Damien's one
>like below.
>
>Thanks,
>
>===
>>From 9df6f09e3a09ed804aba4b56ff7cd9524c002e69 Mon Sep 17 00:00:00 2001
>From: Jaegeuk Kim <jaegeuk@...nel.org>
>Date: Tue, 26 Nov 2019 15:01:42 -0800
>Subject: [PATCH] f2fs: preallocate DIO blocks when forcing buffered_io
>
>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>
>Signed-off-by: Jaegeuk Kim <jaegeuk@...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 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..0e1b12a4a4d6 100644
>--- a/fs/f2fs/file.c
>+++ b/fs/f2fs/file.c
>@@ -3386,18 +3386,41 @@ 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);
>
>-- 
>2.19.0.605.g01d371f741-goog
>
>

Looks good to me. It also fixes the problem we see in our end.

Reviewed-by: Javier González <javier@...igon.com>