btrfs: look at bi_size for repair decisions
bio_readpage_error currently uses bi_vcnt to decide if it is worth
retrying an I/O. But the vector count is mostly an implementation
artifact - it really should figure out if there is more than a
single sector worth retrying. Use bi_size for that and shift by
PAGE_SHIFT. This really should be blocks/sectors, but given that
btrfs doesn't support a sector size different from the PAGE_SIZE
using the page size keeps the changes to a minimum.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>