ext4: submit and wait for pending disksize-grow I/O on writeback

When the current writeback pass begins beyond the disksize-grow-pending
zeroed EOF block, the ioend worker would otherwise have to wait for the
pending EOF block to complete before it can advance i_disksize.
Otherwise the old EOF block could be exposed as stale data once
i_disksize advances past it.

Therefore, introduce the ioend mechanism for the pending range, tag
ioends that cover the pending zeroed EOF block which straddles
i_disksize with EXT4_IOMAP_IOEND_DISKSIZE_GROW_IO in
ext4_iomap_writeback_submit(), and clear the bit and wake up all waiters
in ext4_iomap_end_bio() when such an ioend completes.

Clearing EXT4_IOMAP_IOEND_DISKSIZE_GROW_IO does not depend on whether
the disksize grow I/O succeeds. That is, even if the I/O fails, we still
allow subsequent writes in the range to update i_disksize. This is
consistent with the previous behavior, and we rely on data_err=abort to
prevent metadata updates when data write failures occur.

In order to avoid the ioend that passes the pending range waiting for a
long time, proactively submit the pending range first in
ext4_iomap_writepages() so it completes in parallel with the rest of the
writeback.

Note that the handling of discarding the zeroed EOF folio will be
processed later, otherwise the bit will be set forever.
EXT4_STATE_DISKSIZE_GROW_PENDING will be set after everthing is done.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260903123543.2302999-23-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

0 files changed, 0 insertions, 0 deletions