Received-SPF: pass (google.com: best guess record for domain of linux-ext4-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 28 Oct 2019 21:50:32 +1100
From:   Matthew Bobrowski <mbobrowski@mbobrowski.org>
To:     tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca
Cc:     linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com
Subject: [PATCH v6 01/11] ext4: reorder map.m_flags checks within
 ext4_iomap_begin()
Message-ID: <7fcb28c72d81123f7882b8420b76860c05f302f8.1572255424.git.mbobrowski@mbobrowski.org>
References: <cover.1572255424.git.mbobrowski@mbobrowski.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <cover.1572255424.git.mbobrowski@mbobrowski.org>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-ext4-owner@vger.kernel.org
Precedence: bulk

For the direct I/O changes that follow in this patch series, we need
to accommodate for the case where the block mapping flags passed
through to ext4_map_blocks() result in m_flags having both
EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN bits set. In order for any
allocated unwritten extents to be converted correctly in the
->end_io() handler, the iomap->type must be set to IOMAP_UNWRITTEN for
cases where the EXT4_MAP_UNWRITTEN bit has been set within
m_flags. Hence the reason why we need to reshuffle this conditional
statement around.

This change is a no-op for DAX as the block mapping flags passed
through to ext4_map_blocks() i.e. EXT4_GET_BLOCKS_CREATE_ZERO never
results in both EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN being set at
once.

Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
---
 fs/ext4/inode.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index abaaf7d96ca4..ee116344c420 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3535,10 +3535,20 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 		iomap->type = delalloc ? IOMAP_DELALLOC : IOMAP_HOLE;
 		iomap->addr = IOMAP_NULL_ADDR;
 	} else {
-		if (map.m_flags & EXT4_MAP_MAPPED) {
-			iomap->type = IOMAP_MAPPED;
-		} else if (map.m_flags & EXT4_MAP_UNWRITTEN) {
+		/*
+		 * Flags passed into ext4_map_blocks() for direct I/O writes
+		 * can result in m_flags having both EXT4_MAP_MAPPED and
+		 * EXT4_MAP_UNWRITTEN bits set. In order for any allocated
+		 * unwritten extents to be converted into written extents
+		 * correctly within the ->end_io() handler, we need to ensure
+		 * that the iomap->type is set appropriately. Hence the reason
+		 * why we need to check whether EXT4_MAP_UNWRITTEN is set
+		 * first.
+		 */
+		if (map.m_flags & EXT4_MAP_UNWRITTEN) {
 			iomap->type = IOMAP_UNWRITTEN;
+		} else if (map.m_flags & EXT4_MAP_MAPPED) {
+			iomap->type = IOMAP_MAPPED;
 		} else {
 			WARN_ON_ONCE(1);
 			return -EIO;
-- 
2.20.1