RE: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data
> -Original Message- > From: Nicholas Mc Guire > Sent: Thursday, January 10, 2019 8:44 PM > To: Leo Li > Cc: Scott Wood ; linuxppc-dev d...@lists.ozlabs.org>; lkml ; moderated > list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE ker...@lists.infradead.org>; Nicholas Mc Guire > Subject: Re: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data > > On Thu, Jan 10, 2019 at 01:43:01PM -0600, Li Yang wrote: > > On Sat, Dec 22, 2018 at 2:02 AM Nicholas Mc Guire > wrote: > > > > > > On Fri, Dec 21, 2018 at 08:29:56PM -0600, Scott Wood wrote: > > > > On Fri, 2018-12-07 at 09:22 +0100, Nicholas Mc Guire wrote: > > > > > devm_kstrdup() may return NULL if internal allocation failed, > > > > > but as machine is from the device tree, and thus RO, > > > > > devm_kstrdup_const() can be used here, which will only copy the > reference. > > > > > > > > Is it really going to only copy the reference? That would require > > > > that > > > > is_kernel_rodata(machine) be true, which it shouldn't be since > > > > it's not part of the kernel image. > > > > > > > I had tried to figure out what is RO and what not but was not able > > > to determine that - from the discussion it seemed that the > > > assumption of RO is correct though I did not ask if it would satisfy > > > is_kernel_rodata() so that explains the incorrect assertion. > > > see > > > > https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fl > > > > kml.org%2Flkml%2F2018%2F12%2F6%2F42&data=02%7C01%7Cleoyang.l > i%40 > > > > nxp.com%7Cf72d70a65d1b47f6883808d6776e9d58%7C686ea1d3bc2b4c6fa92c > d99 > > > > c5c301635%7C0%7C1%7C636827714307963102&sdata=xnaO0Y7q%2Byad > Yv8sF > > > VPFtkfllgnwpEIkkTIgw0K%2Fovg%3D&reserved=0 > > > So then the only option is to check the return and cleanup on > > > allocation failure as the orriginal patch proposed. > > > > Thanks for the good discussion. I will drop the previous patch. But > > would it also be good to just have "soc_dev_attr.machine = machine" > > directly? > > > I think that the intent is to switch to managed devm API so that the cleanup > is > handled properly currently you would get "machine" from > of_property_read_string_index > -> of_property_read_string_helper >-> of_find_property > which does not do any allocation - so there would actually not be anything to > cleanup here - don´t see why your solution would not be suitable given the > current API. the only advantage of the devm_kstrdup() is that underlying > APIs internal changes would have no effect. Thanks. I will sent out a new version. Regards, Leo
Re: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data
On Thu, Jan 10, 2019 at 01:43:01PM -0600, Li Yang wrote: > On Sat, Dec 22, 2018 at 2:02 AM Nicholas Mc Guire wrote: > > > > On Fri, Dec 21, 2018 at 08:29:56PM -0600, Scott Wood wrote: > > > On Fri, 2018-12-07 at 09:22 +0100, Nicholas Mc Guire wrote: > > > > devm_kstrdup() may return NULL if internal allocation failed, but > > > > as machine is from the device tree, and thus RO, devm_kstrdup_const() > > > > can be used here, which will only copy the reference. > > > > > > Is it really going to only copy the reference? That would require that > > > is_kernel_rodata(machine) be true, which it shouldn't be since it's not > > > part > > > of the kernel image. > > > > > I had tried to figure out what is RO and what not but was not > > able to determine that - from the discussion it seemed that the > > assumption of RO is correct though I did not ask if it would > > satisfy is_kernel_rodata() so that explains the incorrect assertion. > > see https://lkml.org/lkml/2018/12/6/42 > > So then the only option is to check the return and cleanup > > on allocation failure as the orriginal patch proposed. > > Thanks for the good discussion. I will drop the previous patch. But > would it also be good to just have "soc_dev_attr.machine = machine" > directly? > I think that the intent is to switch to managed devm API so that the cleanup is handled properly currently you would get "machine" from of_property_read_string_index -> of_property_read_string_helper -> of_find_property which does not do any allocation - so there would actually not be anything to cleanup here - don´t see why your solution would not be suitable given the current API. the only advantage of the devm_kstrdup() is that underlying APIs internal changes would have no effect. thx! hofrat
Re: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data
On Sat, Dec 22, 2018 at 2:02 AM Nicholas Mc Guire wrote: > > On Fri, Dec 21, 2018 at 08:29:56PM -0600, Scott Wood wrote: > > On Fri, 2018-12-07 at 09:22 +0100, Nicholas Mc Guire wrote: > > > devm_kstrdup() may return NULL if internal allocation failed, but > > > as machine is from the device tree, and thus RO, devm_kstrdup_const() > > > can be used here, which will only copy the reference. > > > > Is it really going to only copy the reference? That would require that > > is_kernel_rodata(machine) be true, which it shouldn't be since it's not part > > of the kernel image. > > > I had tried to figure out what is RO and what not but was not > able to determine that - from the discussion it seemed that the > assumption of RO is correct though I did not ask if it would > satisfy is_kernel_rodata() so that explains the incorrect assertion. > see https://lkml.org/lkml/2018/12/6/42 > So then the only option is to check the return and cleanup > on allocation failure as the orriginal patch proposed. Thanks for the good discussion. I will drop the previous patch. But would it also be good to just have "soc_dev_attr.machine = machine" directly? Regards, Leo
Re: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data
On Fri, Dec 21, 2018 at 08:29:56PM -0600, Scott Wood wrote: > On Fri, 2018-12-07 at 09:22 +0100, Nicholas Mc Guire wrote: > > devm_kstrdup() may return NULL if internal allocation failed, but > > as machine is from the device tree, and thus RO, devm_kstrdup_const() > > can be used here, which will only copy the reference. > > Is it really going to only copy the reference? That would require that > is_kernel_rodata(machine) be true, which it shouldn't be since it's not part > of the kernel image. > I had tried to figure out what is RO and what not but was not able to determine that - from the discussion it seemed that the assumption of RO is correct though I did not ask if it would satisfy is_kernel_rodata() so that explains the incorrect assertion. see https://lkml.org/lkml/2018/12/6/42 So then the only option is to check the return and cleanup on allocation failure as the orriginal patch proposed. thanks for clearifying this ! hofrat
Re: [PATCH] soc: fsl: guts: us devm_kstrdup_const() for RO data
On Fri, 2018-12-07 at 09:22 +0100, Nicholas Mc Guire wrote: > devm_kstrdup() may return NULL if internal allocation failed, but > as machine is from the device tree, and thus RO, devm_kstrdup_const() > can be used here, which will only copy the reference. Is it really going to only copy the reference? That would require that is_kernel_rodata(machine) be true, which it shouldn't be since it's not part of the kernel image. -Scott