Commit 53e5cca5 authored Nov 05, 2019 by Matthew Bobrowski Committed by Theodore Ts'o Nov 05, 2019

ext4: reorder map.m_flags checks within ext4_iomap_begin()



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>
Link: https://lore.kernel.org/r/1309ad80d31a637b2deed55a85283d582a54a26a.1572949325.git.mbobrowski@mbobrowski.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent f21bdbba

fs/ext4/inode.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -3577,10 +3577,20 @@ retry:
		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;

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