scsi_debug: fix do_device_access() with wrap around range
do_device_access() is a function that abstracts copying SG list from/to ramdisk storage (fake_storep). It must deal with the ranges exceeding actual fake_storep size, because such ranges are valid if virtual_gb is set greater than zero, and they should be treated as fake_storep is repeatedly mirrored up to virtual size. Unfortunately, it can't deal with the range which wraps around the end of fake_storep. A wrap around range is copied by two sg_copy_{from,to}_buffer() calls, but sg_copy_{from,to}_buffer() can't copy from/to in the middle of SG list, therefore the second call can't copy correctly. This fixes it by using sg_pcopy_{from,to}_buffer() that can copy from/to the middle of SG list. This also simplifies the assignment of sdb->resid in fill_from_dev_buffer(). Because fill_from_dev_buffer() is now only called once per command execution cycle. So it is not necessary to take care to decrease sdb->resid if fill_from_dev_buffer() is called more than once. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: "James E.J. Bottomley" <JBottomley@parallels.com> Cc: Douglas Gilbert <dgilbert@interlog.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Horia Geanta <horia.geanta@freescale.com> Cc: Imre Deak <imre.deak@intel.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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