ext4: avoid unnecessary transaction in ext4_map_blocks() for unwritten extents

When ext4_map_blocks() finds an unwritten extent in the extent cache and
the caller is willing to accept unwritten extents without conversion,
there is no need to start a journal transaction since no metadata update
is required. This avoids unnecessary transaction overhead in the
upcoming iomap writeback path when overwriting already-allocated
unwritten extents.

One thing to be careful about, as the comment in ext4_map_blocks()
states, if the flags contain EXT4_GET_BLOCKS_CREATE, the function will
mark @map as mapped.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Tested-by: syzbot@syzkaller.appspotmail.com
Link: https://patch.msgid.link/20261009103033.2920530-8-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

0 files changed, 0 insertions, 0 deletions