@@ -16,6 +16,7 @@
#include <string.h>
#include <ctype.h>
#include <getopt.h>
+#include <sys/ioctl.h>
#define __STDC_FORMAT_MACROS 1
#include <inttypes.h>
@@ -26,6 +27,7 @@
#include "sg_lib.h"
#include "sg_cmds_basic.h"
#include "sg_cmds_extra.h"
+#include "sg_io_linux.h"
static const char * version_str = "0.44 20140202";
@@ -1029,6 +1031,8 @@
struct sg_simple_inquiry_resp inq_resp;
const char * cp;
struct opts_t opts;
+ int omode = 0;
+ const char *omode_desc = "rw";
memset(&opts, 0, sizeof(opts));
opts.prin = 1;
@@ -1292,10 +1296,31 @@
sg_cmds_close_device(sg_fd);
}
- if ((sg_fd = sg_cmds_open_device(device_name, 0 /* rw */,
+#ifdef SG_LIB_LINUX
+ /*
+ * PRIN commands do not provoke device changes, so we should avoid to
+ * open the device read-write so that the Linux kernel does not
generate
+ * a change event.
+ * Older kernel do not support PRIN commands submission on a read-only
+ * opened device, so don't try in this case.
+ */
+ int v;
+ if (opts.prin) {
+ sg_fd = sg_cmds_open_device(device_name, 1, opts.verbose);
+ if (sg_fd >= 0) {
+ if (ioctl(sg_fd, SG_GET_VERSION_NUM, &v) >= 0 && v >= 30000) {
+ omode = 1;
+ omode_desc = "ro";
+ }
+ sg_cmds_close_device(sg_fd);
+ }
+ }
+#endif
+
+ if ((sg_fd = sg_cmds_open_device(device_name, omode,
opts.verbose)) < 0) {
- pr2serr("sg_persist: error opening file (rw): %s: %s\n",
device_name,
- safe_strerror(-sg_fd));
+ pr2serr("sg_persist: error opening file (%s): %s: %s\n",
omode_desc,
+ device_name, safe_strerror(-sg_fd));
Doug, would this patch address the Linux kernel backward-compatibility concern you raised ? Note, you would have to substitute the 3000 version by the appropriate version that introduced support for prin commands submitted on a open-ro device ... return SG_LIB_FILE_ERROR; } Best regards, Christophe Varoqui www.opensvc.com On Sun, May 4, 2014 at 8:01 PM, Christophe Varoqui < christophe.varoqui@opensvc.com> wrote: > Indeed, I'd rather let udev do its work on legitimate device changes. > Problem is, this change event caused by sg_persist prin commands in not > legitimate : no device change can be caused by interrogating the disk pr > status. > > Doug informed me newer kernels accept prin commands inside a > open-ro=>close sequence, which I now verified by testing with the patch I > sent ... but older kernels do not. My patch is thus not backward compatible > as-is. > > Any advice on how to treat this backward-compatibility issue ? > > For information, here's a more recent version of the patch I sent to Doug > earlier to address not-Linux platform behaviour stability : > > --- sg_persist.c.orig 2014-05-04 01:10:01.987981956 +0200 > +++ sg_persist.c 2014-05-04 08:41:29.482017943 +0200 > @@ -1029,6 +1029,8 @@ > struct sg_simple_inquiry_resp inq_resp; > const char * cp; > struct opts_t opts; > + int omode = 0; > + const char *omode_desc = "rw"; > > memset(&opts, 0, sizeof(opts)); > opts.prin = 1; > @@ -1292,10 +1294,17 @@ > sg_cmds_close_device(sg_fd); > } > > - if ((sg_fd = sg_cmds_open_device(device_name, 0 /* rw */, > +#ifdef SG_LIB_LINUX > + if (opts.prin) { > + omode = 1; > + omode_desc = "ro"; > + } > +#endif > + > + if ((sg_fd = sg_cmds_open_device(device_name, omode, > opts.verbose)) < 0) { > - pr2serr("sg_persist: error opening file (rw): %s: %s\n", > device_name, > - safe_strerror(-sg_fd)); > + pr2serr("sg_persist: error opening file (%s): %s: %s\n", > omode_desc, > + device_name, safe_strerror(-sg_fd)); > return SG_LIB_FILE_ERROR; > } > > Regards, > Christophe Varoqui > www.opensvc.com > > > > On Sun, May 4, 2014 at 7:23 PM, Zdenek Kabelac <zkabelac@redhat.com>wrote: > >> Dne 4.5.2014 18:54, Hannes Reinecke napsal(a): >> >> On 05/04/2014 01:34 AM, Christophe Varoqui wrote: >>> >>>> It seems sg_persist is doing an "open rw => close" for --in commands, >>>> causing a kernel change-event. >>>> >>> Yep. >>> >>> Look for 'watch' in the udev rules, that's precisely what it's doing. >>> >>> (Bloody annoying if you ask me. Generally I recommend to remove that >>> thing >>> from the rules). >>> >> >> When watch rule is disabled/removed in udev rules - your udev db becomes >> invalid when i.e. you run command like 'mkfs' - since the udev db will >> not be updated to list information about newly formatted filesystem. >> >> Of course there are many cases where disabling watch rule makes sense >> (i.e. you export lots of disks to virtual guests) - but unless you are >> familiar with udev and you know what you are doing - think twice before >> disabling. >> >> Zdenek >> >> -- >> dm-devel mailing list >> dm-devel@redhat.com >> https://www.redhat.com/mailman/listinfo/dm-devel >> > > -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel