ext2: preserve completed DIO bytes when buffered fallback fails

ext2_dio_write_iter() can complete part of a direct write before
falling back to buffered I/O for a hole inside i_size. If
generic_perform_write() then fails, its error overwrites the completed
direct-I/O byte count.

For example, on a full filesystem, an 8 KiB write to a file with an
allocated 4 KiB prefix and a 4 KiB hole overwrites the prefix but returns
ENOSPC and leaves the file position unchanged. GNU dd with oflag=direct
consequently reports zero bytes written.

Preserve a positive direct-I/O result and return the buffered error
when no bytes were direct-written. This restores the fallback policy of
generic_file_write_iter(), which ext2 used before its iomap conversion.

Fixes: fb5de4358e1a ("ext2: Move direct-io to use iomap")
Cc: stable@vger.kernel.org
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
Link: https://patch.msgid.link/20261102061555.55183-1-dennylin0707@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>

0 files changed, 0 insertions, 0 deletions