| Message ID | 20200904200554.168979-1-tom.ty89@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/4] scsi: sg: fix BLKSECTGET ioctl | expand |
On 2020-09-04 4:05 p.m., 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@gmail.com> Acked-by: Douglas Gilbert <dgilbert@interlog.com> > --- > 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, >
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@gmail.com> > --- > 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@vger.kernel.org, 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" Thanks, Bart.
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@gmail.com> >> --- >> 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@vger.kernel.org, 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 :-) Doug Gilbert
It was my concern as well, that for this sort of "backwards-incompatible reason", it has been kept broken intentionally. 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@interlog.com> 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@gmail.com> > >> --- > >> 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@vger.kernel.org, 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
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@interlog.com), notes: And bumping the version number is appropriate for an interface tweak/correction. 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. 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@interlog.com> 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@gmail.com> >>>> --- >>>> 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@vger.kernel.org, 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 >
On Sun, 6 Sep 2020 at 13:09, Douglas Gilbert <dgilbert@interlog.com> 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@interlog.com), 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@interlog.com> 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@gmail.com> > >>>> --- > >>>> 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@vger.kernel.org, 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 > > >
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,
It should give out the maximum number of sectors per request instead of maximum number of bytes. Signed-off-by: Tom Yan <tom.ty89@gmail.com> --- drivers/scsi/sg.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)