On 09/28/2016 07:19 PM, Darrick J. Wong wrote:
After much discussion, it seems that the fallocate feature flag
FALLOC_FL_ZERO_RANGE maps nicely to SCSI WRITE SAME; and the feature
FALLOC_FL_PUNCH_HOLE maps nicely to the devices that have been
whitelisted for zeroing SCSI UNMAP. Punch still requires that
FALLOC_FL_KEEP_SIZE is set. A length that goes past the end of the
device will be clamped to the device size if KEEP_SIZE is set; or will
return -EINVAL if not. Both start and length must be aligned to the
device's logical block size.
Since the semantics of fallocate are fairly well established already,
wire up the two pieces. The other fallocate variants (collapse range,
insert range, and allocate blocks) are not supported.
For the FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE |
FALLOC_FL_NO_HIDE_STALE case, it's probably safer not to try to send a
discard to block devices that do not support discard in order not to hit
block driver bugs. But that's something we can still discuss later. Hence:
Reviewed-by: Bart Van Assche <bart.vanass...@sandisk.com>
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