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ext2: preserve completed DIO bytes when buffered fallback fails

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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: fb5de4358e ("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>
This commit is contained in:
Hungyu Lin 2026-11-02 06:15:55 +00:00 committed by Jan Kara
parent 5406ffab82
commit cbf04dde8b
1 changed files with 2 additions and 1 deletions
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3
fs/ext2/file.c
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@ -145,7 +145,8 @@ static ssize_t ext2_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
pos = iocb->ki_pos;
status = generic_perform_write(iocb, from);
if (unlikely(status < 0)) {
ret = status;
if (!ret)
ret = status;
goto out_unlock;
}