[PATCH] vscsi and symlinks

[PATCH] vscsi and symlinks

[James Harper]

By default, vscsi expects to be passed the final device name (eg
/dev/st3) instead of one of the various udev symlinks (eg
/dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following patch
resolves the path to the real path if the name starts with /dev/

James

--- a/tools/python/xen/util/vscsi_util.py  2010-12-03 23:26:46.391655087
+1100
+++ b/tools/python/xen/util/vscsi_util.py  2011-02-07 12:20:37.599527204
+1100
@@ -158,6 +158,8 @@


 def vscsi_get_hctl_and_devname_by(target, scsi_devices = None):
+    if target.startswith('/dev/'):
+        target = os.path.realpath(target)
     if scsi_devices is None:
         if len(target.split(':')) == 4:
             scsi_devices = _vscsi_get_scsidevices_by_lsscsi(target)

Re: [PATCH] vscsi and symlinks

[Ian Campbell]

On Mon, 2011-02-07 at 01:24 +0000, James Harper wrote:
> By default, vscsi expects to be passed the final device name (eg
> /dev/st3) instead of one of the various udev symlinks (eg
> /dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following patch
> resolves the path to the real path if the name starts with /dev/

This needs a signed-off-by.

> James
> 
> --- a/tools/python/xen/util/vscsi_util.py  2010-12-03 23:26:46.391655087
> +1100
> +++ b/tools/python/xen/util/vscsi_util.py  2011-02-07 12:20:37.599527204
> +1100
> @@ -158,6 +158,8 @@
> 
> 
>  def vscsi_get_hctl_and_devname_by(target, scsi_devices = None):
> +    if target.startswith('/dev/'):
> +        target = os.path.realpath(target)

Any reason not to just unconditionally resolve symlinks in every target
to the underlying device?

Thanks,
Ian.

Re: [PATCH] vscsi and symlinks

[Ian Campbell]

(Adding xen-devel back since I guess you didn't mean to drop)

On Mon, 2011-02-07 at 09:43 +0000, James Harper wrote:
> I think target isn't always a file. It can be a scsi ID like 0:1:2:3.
> I think it can be other types of specifier too.

OK. So perhaps:

if os.path.islink(target):
	target = os.path.realpath(target)

?

Ian.

RE: [PATCH] vscsi and symlinks

[James Harper]

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> 
> On Mon, 2011-02-07 at 09:43 +0000, James Harper wrote:
> > I think target isn't always a file. It can be a scsi ID like 0:1:2:3.
> > I think it can be other types of specifier too.
> 
> OK. So perhaps:
> 
> if os.path.islink(target):
> 	target = os.path.realpath(target)
> 

I guess. I know it's a long shot but what if there was a symlink called 0:1:2:3? While that is unlikely, there might be other incantations used by vscsi that could ambiguously be the filename of a symlink or not. I'd be happier if realpath was only used if an absolute path was specified. Who's going to want to specify a relative path anyway... what would it be relative to?

James

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RE: [PATCH] vscsi and symlinks

[Ian Campbell]

On Mon, 2011-02-07 at 11:28 +0000, James Harper wrote:
> > 
> > On Mon, 2011-02-07 at 09:43 +0000, James Harper wrote:
> > > I think target isn't always a file. It can be a scsi ID like 0:1:2:3.
> > > I think it can be other types of specifier too.
> > 
> > OK. So perhaps:
> > 
> > if os.path.islink(target):
> > 	target = os.path.realpath(target)
> > 
> 
> I guess. I know it's a long shot but what if there was a symlink
> called 0:1:2:3? While that is unlikely, there might be other
> incantations used by vscsi that could ambiguously be the filename of a
> symlink or not. I'd be happier if realpath was only used if an
> absolute path was specified. Who's going to want to specify a relative
> path anyway... what would it be relative to?

Yes, good points. I guess we could go with target[0] == '/' but I think
you are right to go with the conservative approach of checking for /dev/
unless/until someone shows up with a bug suggesting we do otherwise.

Ian.

RE: [PATCH] vscsi and symlinks [and 1 more messages]

[Ian Jackson]

James Harper writes ("RE: [Xen-devel] [PATCH] vscsi and symlinks"):
> With signed-off-by line :)
> 
> By default, vscsi expects to be passed the final device name (eg
> /dev/st3) instead of one of the various udev symlinks (eg
> /dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following patch
> resolves the path to the real path if the name starts with /dev/

Thanks, applied.

Ian.

Re: [PATCH] vscsi and symlinks

[Ian Jackson]

James Harper writes ("[Xen-devel] [PATCH] vscsi and symlinks"):
> By default, vscsi expects to be passed the final device name (eg
> /dev/st3) instead of one of the various udev symlinks (eg
> /dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following patch
> resolves the path to the real path if the name starts with /dev/

Thanks.  I would have applied this patch but you didn't provide a
"signed-off-by", to confirm that your contribution is in accordance
with the Developer's Certificate of Origin.

>From Documentation/SubmittingPatches in the Linux kernel tree:
 
        Developer's Certificate of Origin 1.1
 
        By making a contribution to this project, I certify that:
 
        (a) The contribution was created in whole or in part by me and I
            have the right to submit it under the open source license
            indicated in the file; or
 
        (b) The contribution is based upon previous work that, to the best
            of my knowledge, is covered under an appropriate open source
            license and I have the right under that license to submit that
            work with modifications, whether created in whole or in part
            by me, under the same open source license (unless I am
            permitted to submit under a different license), as indicated
            in the file; or
 
        (c) The contribution was provided directly to me by some other
            person who certified (a), (b) or (c) and I have not modified
            it.
 
        (d) I understand and agree that this project and the contribution
            are public and that a record of the contribution (including all
            personal information I submit with it, including my sign-off) is
            maintained indefinitely and may be redistributed consistent with
            this project or the open source license(s) involved.

Ian.

RE: [PATCH] vscsi and symlinks

[James Harper]

With signed-off-by line :)

By default, vscsi expects to be passed the final device name (eg
/dev/st3) instead of one of the various udev symlinks (eg
/dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following patch
resolves the path to the real path if the name starts with /dev/

Signed-off-by: James Harper <james.harper@bendigoit.com.au>

--- a/tools/python/xen/util/vscsi_util.py  2010-12-03 23:26:46.391655087
+1100
+++ b/tools/python/xen/util/vscsi_util.py  2011-02-07 12:20:37.599527204
+1100
@@ -158,6 +158,8 @@


 def vscsi_get_hctl_and_devname_by(target, scsi_devices = None):
+    if target.startswith('/dev/'):
+        target = os.path.realpath(target)
     if scsi_devices is None:
         if len(target.split(':')) == 4:
             scsi_devices = _vscsi_get_scsidevices_by_lsscsi(target)



> -----Original Message-----
> From: Ian Jackson [mailto:Ian.Jackson@eu.citrix.com]
> Sent: Tuesday, 8 February 2011 03:23
> To: James Harper
> Cc: xen-devel@lists.xensource.com
> Subject: Re: [Xen-devel] [PATCH] vscsi and symlinks
> 
> James Harper writes ("[Xen-devel] [PATCH] vscsi and symlinks"):
> > By default, vscsi expects to be passed the final device name (eg
> > /dev/st3) instead of one of the various udev symlinks (eg
> > /dev/tape/by-path/pci-0000:01:08.0-scsi-0:0:2:0-st). The following
patch
> > resolves the path to the real path if the name starts with /dev/
> 
> Thanks.  I would have applied this patch but you didn't provide a
> "signed-off-by", to confirm that your contribution is in accordance
> with the Developer's Certificate of Origin.
> 
> From Documentation/SubmittingPatches in the Linux kernel tree:
> 
>         Developer's Certificate of Origin 1.1
> 
>         By making a contribution to this project, I certify that:
> 
>         (a) The contribution was created in whole or in part by me and
I
>             have the right to submit it under the open source license
>             indicated in the file; or
> 
>         (b) The contribution is based upon previous work that, to the
best
>             of my knowledge, is covered under an appropriate open
source
>             license and I have the right under that license to submit
that
>             work with modifications, whether created in whole or in
part
>             by me, under the same open source license (unless I am
>             permitted to submit under a different license), as
indicated
>             in the file; or
> 
>         (c) The contribution was provided directly to me by some other
>             person who certified (a), (b) or (c) and I have not
modified
>             it.
> 
>         (d) I understand and agree that this project and the
contribution
>             are public and that a record of the contribution
(including all
>             personal information I submit with it, including my
sign-off) is
>             maintained indefinitely and may be redistributed
consistent with
>             this project or the open source license(s) involved.
> 
> Ian.