Tejun Heo wrote:
Misc ATAPI commands may try to transfer more bytes than requested. For PIO which is performed by libata HSM, this is worked around by draining extra bytes from __atapi_pio_bytes(). This patch implements drain buffer to perform draining for DMA and PIO-over-DMA cases. One page is allocated w/ GFP_DMA32 during libata core layer initialization. On host registration, this drain page is DMA mapped and ATAPI_MAX_DRAIN_PAGES sg entries are reserved. ata_sg_setup_extra() uses these extra sg entries to map the drain page ATAPI_MAX_DRAIN_PAGES times, extending sg list by ATAPI_MAX_DRAIN bytes. This allows both DMA and PIO-over-DMA misc ATAPI commands to overflow by ATAPI_MAX_DRAIN bytes just like PIO commands. Signed-off-by: Tejun Heo <htejun@xxxxxxxxx> --- drivers/ata/libata-core.c | 116 ++++++++++++++++++++++++++++++++++++++++----- drivers/ata/libata-scsi.c | 14 ++++-- include/linux/libata.h | 4 +- 3 files changed, 116 insertions(+), 18 deletions(-)
ACK this patch and #14 (implement ATAPI per-command-type DMA horkages), but I am dropping both due to the need to be rediffed against latest #upstream (including recent #upstream-fixes changes).
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