On a ranged download the metadata decoder stored the response's
Content-Length (the length of the range, not the blob) in the object's
size and only corrected it from the Content-Range total afterwards.
Object.Size() is read concurrently by the VFS cache and chunked reader
while a download is in progress, so with --vfs-read-chunk-size a reader
could observe the chunk length (e.g. 67108864 for 64M chunks) as the
object size. The VFS cache then logged
vfs cache: cached file (N) is unexpectedly larger than the remote
object (67108864). The cached file is likely corrupted after an
unclean shutdown; recovering ...
and truncated the read request against the bogus size, breaking
sequential reads of large blobs with --vfs-cache-mode full.
This applies the Content-Range correction before the size is stored so
the range length is never published as the object size.
Nick Craig-Wood
bee45bccfd