linux-ext4 - [PATCH v4 6/9] f2fs: don't allow DIO reads but not DIO writes

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Message-Id: <20220722071228.146690-7-ebiggers@kernel.org>
Date:   Fri, 22 Jul 2022 00:12:25 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-xfs@...r.kernel.org, linux-api@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Keith Busch <kbusch@...nel.org>
Subject: [PATCH v4 6/9] f2fs: don't allow DIO reads but not DIO writes

From: Eric Biggers <ebiggers@...gle.com>

Currently, if an f2fs filesystem is mounted with the mode=lfs and
io_bits mount options, DIO reads are allowed but DIO writes are not.
Allowing DIO reads but not DIO writes is an unusual restriction, which
is likely to be surprising to applications, namely any application that
both reads and writes from a file (using O_DIRECT).  This behavior is
also incompatible with the proposed STATX_DIOALIGN extension to statx.
Given this, let's drop the support for DIO reads in this configuration.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/f2fs/file.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 5e5c97fccfb4ee..ad0212848a1ab9 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -823,7 +823,6 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
 				struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	int rw = iov_iter_rw(iter);
 
 	if (!fscrypt_dio_supported(inode))
 		return true;
@@ -841,7 +840,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
 	 */
 	if (f2fs_sb_has_blkzoned(sbi))
 		return true;
-	if (f2fs_lfs_mode(sbi) && (rw == WRITE)) {
+	if (f2fs_lfs_mode(sbi)) {
 		if (block_unaligned_IO(inode, iocb, iter))
 			return true;
 		if (F2FS_IO_ALIGNED(sbi))
-- 
2.37.0