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@xxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
---
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
