[Bug 219652] READ CAPACITY(16) not used on large USB-attached drive in recent kernels

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=219652

--- Comment #12 from michael.christie@oracle.com ---
On 1/2/25 9:30 PM, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=219652
> 
> --- Comment #10 from Alan Stern (stern@rowland.harvard.edu) ---
> Re comment #8: I would like to know the answers to the questions asked in
> comment #4 about the bad kernel:
> 
>    In sd_read_capacity(), does sd_try_rc16_first() return true?
> 
>    And why doesn't the "Very big device. Trying to use READ CAPACITY(16)"
>    line,> along with the subsequent call to read_capacity_16(), get executed
>    in the bad
> kernel?

I see it.

With the new code we think the command is failing. We then retry the command 3
times
like you described you saw in the trace. Then because on the 3rd retry we get
0xfffffffe instead of 0xffffffff, we don't hit the check below like I mentioned
before:

                sector_size = read_capacity_10(sdkp, sdp, buffer);
                if (sector_size == -EOVERFLOW)
                        goto got_data;
                if (sector_size < 0)
                        return;
                if ((sizeof(sdkp->capacity) > 4) &&
                    (sdkp->capacity > 0xffffffffULL)) {
                        int old_sector_size = sector_size;
                        sd_printk(KERN_NOTICE, sdkp, "Very big device. "
                                        "Trying to use READ CAPACITY(16).\n");
                        sector_size = read_capacity_16(sdkp, sdp, lim, buffer);

With the old kernel, we saw the first try succeed. We then saw the 0xffffffff
and then tried read_capacity_16 above.

And the reason for the difference was that with the new code, I forgot to
add a check for if there was even an error. We ended up always retrying
3 times and that lead us to get the 0xfffffffe value on that last retry.

so we need:

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index adee6f60c966..2dcf225c7017 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -210,6 +210,9 @@ static int scsi_check_passthrough(struct scsi_cmnd *scmd,
        struct scsi_sense_hdr sshdr;
        enum sam_status status;

+       if (!scmd->result)
+               return 0;
+
        if (!failures)
                return 0;

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