On Fri, Dec 19, 2025 at 11:29:04AM -0800, Eric Biggers wrote: > When correcting a data block, the FEC code performs optimally when it > has enough buffers to hold all the needed RS blocks. That number of > buffers is '1 << (v->data_dev_block_bits - DM_VERITY_FEC_BUF_RS_BITS)'. > > However, since v->data_dev_block_bits isn't a compile-time constant, the > code actually used PAGE_SHIFT instead. > > With the traditional PAGE_SIZE == data_block_size == 4096, this was > fine. However, when PAGE_SIZE > data_block_size, this wastes space. > E.g., with data_block_size == 4096 && PAGE_SIZE == 16384, struct > dm_verity_fec_io is 9240 bytes, when in fact only 3096 bytes are needed. > > Fix this by making dm_verity_fec_io::bufs a variable-length array. > > This makes the macros DM_VERITY_FEC_BUF_MAX and > fec_for_each_extra_buffer() no longer apply, so remove them. For > consistency, and because DM_VERITY_FEC_BUF_PREALLOC is fixed at 1 and > was already assumed to be 1 (considering that mempool_alloc() shouldn't > be called in a loop), also remove the related macros > DM_VERITY_FEC_BUF_PREALLOC and fec_for_each_prealloc_buffer(). > > Signed-off-by: Eric Biggers <[email protected]>
Reviewed-by: Sami Tolvanen <[email protected]> Sami
