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Date:   Tue, 12 May 2020 22:43:20 -0700
From:   ira.weiny@...el.com
To:     linux-ext4@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>
Cc:     Ira Weiny <ira.weiny@...el.com>, Al Viro <viro@...iv.linux.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/9] fs/ext4: Update ext4_should_use_dax()

From: Ira Weiny <ira.weiny@...el.com>

S_DAX should only be enabled when the underlying block device supports
dax.

Change ext4_should_use_dax() to check for device support prior to the
over riding mount option.

While we are at it change the function to ext4_should_enable_dax() as
this better reflects the ask as well as matches xfs.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes from RFC
	Change function name to 'should enable'
	Clean up bool conversion
	Reorder this for better bisect-ability
---
 fs/ext4/inode.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a10ff12194db..d3a4c2ed7a1c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4398,10 +4398,8 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
 		!ext4_test_inode_state(inode, EXT4_STATE_XATTR));
 }
 
-static bool ext4_should_use_dax(struct inode *inode)
+static bool ext4_should_enable_dax(struct inode *inode)
 {
-	if (!test_opt(inode->i_sb, DAX_ALWAYS))
-		return false;
 	if (!S_ISREG(inode->i_mode))
 		return false;
 	if (ext4_should_journal_data(inode))
@@ -4412,7 +4410,13 @@ static bool ext4_should_use_dax(struct inode *inode)
 		return false;
 	if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
 		return false;
-	return true;
+	if (!bdev_dax_supported(inode->i_sb->s_bdev,
+				inode->i_sb->s_blocksize))
+		return false;
+	if (test_opt(inode->i_sb, DAX_ALWAYS))
+		return true;
+
+	return false;
 }
 
 void ext4_set_inode_flags(struct inode *inode)
@@ -4430,7 +4434,7 @@ void ext4_set_inode_flags(struct inode *inode)
 		new_fl |= S_NOATIME;
 	if (flags & EXT4_DIRSYNC_FL)
 		new_fl |= S_DIRSYNC;
-	if (ext4_should_use_dax(inode))
+	if (ext4_should_enable_dax(inode))
 		new_fl |= S_DAX;
 	if (flags & EXT4_ENCRYPT_FL)
 		new_fl |= S_ENCRYPTED;
-- 
2.25.1

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