On Thu, 30 Aug 2012 09:09:39 -0700
Ronnie Sahlberg <ronniesahlberg@xxxxxxxxx> wrote:
> Fix a bug in COMPARE-AND-WRITE. If the compare fails, we have to abort with a sense code immediately and we should NOT continue to over-write the backing store with the mismatching data.
>
> IF the data is not matching, we also should compute at which offset the first mismatch in the buffer occurs.
> This is to be reported in the INFORMATION field (bytes 3-7) in the sense buffer in a later patch.
>
> Signed-off-by: Ronnie Sahlberg <ronniesahlberg@xxxxxxxxx>
> ---
> usr/bs_rdwr.c | 25 +++++++++++++++++++++++--
> 1 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/usr/bs_rdwr.c b/usr/bs_rdwr.c
> index a79dd02..c7d72e6 100644
> --- a/usr/bs_rdwr.c
> +++ b/usr/bs_rdwr.c
> @@ -65,6 +65,7 @@ static void bs_rdwr_request(struct scsi_cmd *cmd)
> int result = SAM_STAT_GOOD;
> uint8_t key;
> uint16_t asc;
> + uint32_t info = 0;
> char *tmpbuf;
> size_t blocksize;
> uint64_t offset = cmd->offset;
> @@ -117,12 +118,32 @@ static void bs_rdwr_request(struct scsi_cmd *cmd)
>
> ret = pread64(fd, tmpbuf, length, offset);
>
> - if (ret != length)
> + if (ret != length) {
> set_medium_error(&result, &key, &asc);
> - else if (memcmp(scsi_get_out_buffer(cmd), tmpbuf, length)) {
> + free(tmpbuf);
> + break;
> + }
> +
> + if (memcmp(scsi_get_out_buffer(cmd), tmpbuf, length)) {
> + uint32_t pos = 0;
> + char *spos = scsi_get_out_buffer(cmd);
> + char *dpos = tmpbuf;
> +
> + /* data differed, this is assumed to be 'rare' so use a
> + much more expensive byte-by-byte comparasion to find
> + out at which offset the data differs.
> + */
Can you use Linux kernel comment style?
/*
* comment
* comment
*/
> + while (pos < length) {
> + if (*spos++ != *dpos++)
> + break;
> + pos++;
> + }
How about the simpler code like this?
for (pos = 0; pos < length && *spos++ == *dposs; pos++)
;
> + info = pos;
> result = SAM_STAT_CHECK_CONDITION;
> key = MISCOMPARE;
> asc = ASC_MISCOMPARE_DURING_VERIFY_OPERATION;
> + free(tmpbuf);
> + break;
> }
>
> if (cmd->scb[1] & 0x10)
> --
> 1.7.3.1
>
> --
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