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Subject[PATCH 3/3] scsi_debug: fix do_device_access() with wrap around range
Date
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.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: linux-scsi@vger.kernel.org
---
drivers/scsi/scsi_debug.c | 43 ++++++++++++++++++++++++++++++++++++-------
1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 21239b3..c1efaf8 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1614,24 +1614,48 @@ static int check_device_access_params(struct sdebug_dev_info *devi,
return 0;
}

+/* Returns number of bytes copied or -1 if error. */
static int do_device_access(struct scsi_cmnd *scmd,
struct sdebug_dev_info *devi,
unsigned long long lba, unsigned int num, int write)
{
int ret;
unsigned long long block, rest = 0;
- int (*func)(struct scsi_cmnd *, unsigned char *, int);
+ struct scsi_data_buffer *sdb;
+ enum dma_data_direction dir;
+ size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
+ off_t);
+
+ if (write) {
+ sdb = scsi_out(scmd);
+ dir = DMA_TO_DEVICE;
+ func = sg_pcopy_to_buffer;
+ } else {
+ sdb = scsi_in(scmd);
+ dir = DMA_FROM_DEVICE;
+ func = sg_pcopy_from_buffer;
+ }

- func = write ? fetch_to_dev_buffer : fill_from_dev_buffer;
+ if (!sdb->length)
+ return 0;
+ if (!(scsi_bidi_cmnd(scmd) || scmd->sc_data_direction == dir))
+ return -1;

block = do_div(lba, sdebug_store_sectors);
if (block + num > sdebug_store_sectors)
rest = block + num - sdebug_store_sectors;

- ret = func(scmd, fake_storep + (block * scsi_debug_sector_size),
- (num - rest) * scsi_debug_sector_size);
- if (!ret && rest)
- ret = func(scmd, fake_storep, rest * scsi_debug_sector_size);
+ ret = func(sdb->table.sgl, sdb->table.nents,
+ fake_storep + (block * scsi_debug_sector_size),
+ (num - rest) * scsi_debug_sector_size, 0);
+ if (ret != (num - rest) * scsi_debug_sector_size)
+ return ret;
+
+ if (rest) {
+ ret += func(sdb->table.sgl, sdb->table.nents,
+ fake_storep, rest * scsi_debug_sector_size,
+ (num - rest) * scsi_debug_sector_size);
+ }

return ret;
}
@@ -1888,7 +1912,12 @@ static int resp_read(struct scsi_cmnd *SCpnt, unsigned long long lba,
read_lock_irqsave(&atomic_rw, iflags);
ret = do_device_access(SCpnt, devip, lba, num, 0);
read_unlock_irqrestore(&atomic_rw, iflags);
- return ret;
+ if (ret == -1)
+ return DID_ERROR << 16;
+
+ scsi_in(SCpnt)->resid = scsi_bufflen(SCpnt) - ret;
+
+ return 0;
}

static void dump_sector(unsigned char *buf, int len)
--
1.8.1.4


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