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Message-Id: <1461472078-20104-1-git-send-email-tytso@mit.edu>
Date:	Sun, 24 Apr 2016 00:27:58 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:	Theodore Ts'o <tytso@....edu>
Subject: [PATCH] ext4: refuse O_DIRECT opens for mode where DIO doesn't work

Certain ext4 modes (encryption, data=journal, inline data) cause
Direct I/O to be a no-op.  Instead of making DIO fail silently, make
the open with the O_DIRECT flag fail with EINVAL.

This will avoid surprises to application programs, and also signal to
xfstests not to try O_DIRECT tests for file system modes where it
doesn't work (and could result in test failures).

Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 fs/ext4/file.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index fa2208b..4113676 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -372,7 +372,12 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 			return -EACCES;
 		if (ext4_encryption_info(inode) == NULL)
 			return -ENOKEY;
+		if (filp->f_flags & O_DIRECT)
+			return -EINVAL;
 	}
+	if ((ext4_should_journal_data(inode) || ext4_has_inline_data(inode)) &&
+	    (filp->f_flags & O_DIRECT))
+		return -EINVAL;
 
 	dir = dget_parent(file_dentry(filp));
 	if (ext4_encrypted_inode(d_inode(dir)) &&
-- 
2.5.0

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