On Sun, 6 Sep 2020 at 13:09, Douglas Gilbert <dgilbert@xxxxxxxxxxxx> wrote: > > On 2020-09-05 9:19 p.m., Tom Yan wrote: > > It was my concern as well, that for this sort of > > "backwards-incompatible reason", it has been kept broken > > intentionally. > > Bumping the sg driver version number is simple: > > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index 20472aaaf630..c9763b85961f 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -11,8 +11,8 @@ > * Copyright (C) 1998 - 2014 Douglas Gilbert > */ > > -static int sg_version_num = 30536; /* 2 digits for each component */ > -#define SG_VERSION_STR "3.5.36" > +static int sg_version_num = 30537; /* 2 digits for each component */ > +#define SG_VERSION_STR "3.5.37" > > /* > * D. P. Gilbert (dgilbert@xxxxxxxxxxxx), notes: > > > And bumping the version number is appropriate for an interface > tweak/correction. I wasn't (and still isn't) sure how much I should bump. Maybe 36000 / 3.6.0 will do? (Seems to deserve the bigger bump) > > I'm rewriting the sg driver currently (12 months and counting) and am up > to version 11 of the _first_ half. So far I'm using a sg_version_num of > > 40000 for the rewritten code. Please keep away from version numbers > 40000 and above. > > The rewritten driver is documented here: > https://doug-gilbert.github.io/sg_v40.html > > and its ioctls are listed in Table 8, including the BLK* ones. Perhaps you > could suggest some corrections. Obviously BLKSSZGET needs to be added > when your patches are accepted. "this ioctl value replicates what a block layer device file (e.g. /dev/sda) will do with the same value. It calls the queue_max_sectors() helper on the owning device's command queue. The resulting number represents the maximum number of logical sectors of a single request that the block layer will accept."? and for BLKSSZGET "the resulting number represents the logical sector size"? > > Doug Gilbert > > > I am not sure if queue_max_sectors() or BLKSECTGET has ever been > > implemented in the block layer to give out the limit in bytes, but it > > certainly isn't the case anymore. > > > > I am not in position to say whether it's "right" or "wrong" to > > implement BLKSECTGET/BLKSSZGET in the sg driver, but they is > > definitely useful in some cases (as long as the queue_* functions work > > for the given underlying device). Is it not okay if they don't > > ultimately work on *some* devices, even when they aren't named SG_*? > > > > Perhaps we can consider having them removed as well (and implement > > them as e.g. SG_GET_MAX_SECTORS and SG_GET_LBS; but IMHO that only > > makes a point if they can be made to work on more than block devices). > > > > > > On Sun, 6 Sep 2020 at 04:37, Douglas Gilbert <dgilbert@xxxxxxxxxxxx> wrote: > >> > >> On 2020-09-05 3:32 p.m., Bart Van Assche wrote: > >>> On 2020-09-04 13:05, Tom Yan wrote: > >>>> It should give out the maximum number of sectors per request > >>>> instead of maximum number of bytes. > >>>> > >>>> Signed-off-by: Tom Yan <tom.ty89@xxxxxxxxx> > >>>> --- > >>>> drivers/scsi/sg.c | 6 ++++-- > >>>> 1 file changed, 4 insertions(+), 2 deletions(-) > >>>> > >>>> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > >>>> index 20472aaaf630..e57831910228 100644 > >>>> --- a/drivers/scsi/sg.c > >>>> +++ b/drivers/scsi/sg.c > >>>> @@ -922,6 +922,7 @@ sg_ioctl_common(struct file *filp, Sg_device *sdp, Sg_fd *sfp, > >>>> int result, val, read_only; > >>>> Sg_request *srp; > >>>> unsigned long iflags; > >>>> + unsigned int max_sectors; > >>>> > >>>> SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp, > >>>> "sg_ioctl: cmd=0x%x\n", (int) cmd_in)); > >>>> @@ -1114,8 +1115,9 @@ sg_ioctl_common(struct file *filp, Sg_device *sdp, Sg_fd *sfp, > >>>> sdp->sgdebug = (char) val; > >>>> return 0; > >>>> case BLKSECTGET: > >>>> - return put_user(max_sectors_bytes(sdp->device->request_queue), > >>>> - ip); > >>>> + max_sectors = min_t(unsigned int, USHRT_MAX, > >>>> + queue_max_sectors(sdp->device->request_queue)); > >>>> + return put_user(max_sectors, ip); > >>>> case BLKTRACESETUP: > >>>> return blk_trace_setup(sdp->device->request_queue, > >>>> sdp->disk->disk_name, > >>> > >>> Is this perhaps a backwards-incompatible change to the kernel ABI, the > >>> kind of change Linus totally disagrees with? > >>> > >>> Additionally, please Cc linux-api for patches that modify the kernel ABI. > >>> >From https://www.kernel.org/doc/man-pages/linux-api-ml.html: "The kernel > >>> source file Documentation/SubmitChecklist notes that all Linux kernel > >>> patches that change userspace interfaces should be CCed to > >>> linux-api@xxxxxxxxxxxxxxx, so that the various parties who are interested > >>> in API changes are informed. For further information, see > >>> https://www.kernel.org/doc/man-pages/linux-api-ml.html"; > >> > >> Hmm, > >> The BLK* ioctl()s in the sg driver were an undocumented addition by others. > >> Plus it is not clear to me why a char device such as the sg driver should > >> be supporting BLK* ioctl(2)s. For example, how should an enclosure react to > >> those ioctls or a WLUN? > >> > >> If they are going to be supported for storage devices and /dev/sdb and > >> /dev/sg2 are the same device then if: > >> blockdev --getmaxsect /dev/sg1 > >> > >> gives a different result to: > >> blockdev --getmaxsect /dev/sdb > >> > >> then I would consider that a bug. So fixing it is making the kernel ABI > >> more consistent :-) > > > > That's exactly my point. They should work identically as the ones > > implemented in the block layer, because of their names. > > > > With that said, sg_version needs to be bumped once the fix gets in, so > > that there's a way to differentiate the "different implementations" in > > userspace. > > > >> > >> Doug Gilbert > >> > >> > >> > > > > Regards, > > Tom > > >
