ext4: pass allocate range as loff_t to ext4_alloc_file_blocks()

ext4: pass allocate range as loff_t to ext4_alloc_file_blocks()

Change ext4_alloc_file_blocks() to accept offset and len in byte
granularity instead of block granularity. This allows callers to pass
byte offsets and lengths directly, and this prepares for moving the
ext4_zero_partial_blocks() call from the while(len) loop for unaligned
append writes, where it only needs to be invoked once before doing block
allocation.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260327102939.1095257-8-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>