* [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit @ 2019-05-10 10:20 Kairui Song 2019-05-10 11:17 ` Bhupesh Sharma 2019-05-13 1:52 ` Dave Young 0 siblings, 2 replies; 7+ messages in thread From: Kairui Song @ 2019-05-10 10:20 UTC (permalink / raw) To: linux-kernel Cc: Rahul Lakkireddy, Ganesh Goudar, David S . Miller, Eric Biederman, Alexey Dobriyan, Andrew Morton, Dave Young, kexec, Kairui Song Device dump allow drivers to add device related dump data to vmcore as they want. This have a potential issue, the data is stored in memory, drivers may append too much data and use too much memory. The vmcore is typically used in a kdump kernel which runs in a pre-reserved small chunk of memory. So as a result it will make kdump unusable at all due to OOM issues. So introduce new device_dump_limit= kernel parameter, and set the default limit to 0, so device dump is not enabled unless user specify the accetable maxiam memory usage for device dump data. In this way user will also have the chance to adjust the kdump reserved memory accordingly. Signed-off-by: Kairui Song <kasong@redhat.com> --- fs/proc/vmcore.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index 3fe90443c1bb..e28695ef2439 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; /* Device Dump list and mutex to synchronize access to list */ static LIST_HEAD(vmcoredd_list); static DEFINE_MUTEX(vmcoredd_mutex); + +/* Device Dump Limit */ +static size_t vmcoredd_limit; #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ /* Device Dump Size */ @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) data_size = roundup(sizeof(struct vmcoredd_header) + data->size, PAGE_SIZE); + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { + ret = -ENOMEM; + goto out_err; + } + /* Allocate buffer for driver's to write their dumps */ buf = vmcore_alloc_buf(data_size); if (!buf) { @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) return ret; } EXPORT_SYMBOL(vmcore_add_device_dump); + +static int __init parse_vmcoredd_limit(char *arg) +{ + char *end; + + if (!arg) + return -EINVAL; + vmcoredd_limit = memparse(arg, &end); + return end > arg ? 0 : -EINVAL; + +} +__setup("device_dump_limit=", parse_vmcoredd_limit); #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ /* Free all dumps in vmcore device dump list */ -- 2.20.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-10 10:20 [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit Kairui Song @ 2019-05-10 11:17 ` Bhupesh Sharma 2019-05-16 8:19 ` Kairui Song 2019-05-13 1:52 ` Dave Young 1 sibling, 1 reply; 7+ messages in thread From: Bhupesh Sharma @ 2019-05-10 11:17 UTC (permalink / raw) To: Kairui Song, linux-kernel Cc: kexec, David S . Miller, Rahul Lakkireddy, Eric Biederman, Andrew Morton, Dave Young, Alexey Dobriyan, Ganesh Goudar Hi Kairui, Thanks for the patch. Please see my comments in-line: On 05/10/2019 03:50 PM, Kairui Song wrote: > Device dump allow drivers to add device related dump data to vmcore as > they want. This have a potential issue, the data is stored in memory, > drivers may append too much data and use too much memory. The vmcore is > typically used in a kdump kernel which runs in a pre-reserved small > chunk of memory. So as a result it will make kdump unusable at all due > to OOM issues. > > So introduce new device_dump_limit= kernel parameter, and set the > default limit to 0, so device dump is not enabled unless user specify > the accetable maxiam ^^^^ acceptable maximum > memory usage for device dump data. In this way user > will also have the chance to adjust the kdump reserved memory > accordingly. Hmmm., this doesn't give much confidence with the PROC_VMCORE_DEVICE_DUMP feature in its current shape. Rather shouldn't we be enabling config PROC_VMCORE_DEVICE_DUMP only under EXPERT mode for now, considering that this feature needs further thrashing and testing with real setups including platforms where drivers append large amounts of data to vmcore: diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig index 817c02b13b1d..c47a12cf7fc0 100644 --- a/fs/proc/Kconfig +++ b/fs/proc/Kconfig @@ -45,7 +45,7 @@ config PROC_VMCORE Exports the dump image of crashed kernel in ELF format. config PROC_VMCORE_DEVICE_DUMP - bool "Device Hardware/Firmware Log Collection" + bool "Device Hardware/Firmware Log Collection" if EXPERT depends on PROC_VMCORE default n help @@ -59,6 +59,12 @@ config PROC_VMCORE_DEVICE_DUMP If you say Y here, the collected device dumps will be added as ELF notes to /proc/vmcore. + Considering that there can be device drivers which append + large amounts of data to vmcore, you should say N here unless + you are reserving a large chunk of memory for crashdump + kernel, because otherwise the crashdump kernel might become + unusable due to OOM issues. + May be you can add a 'Fixes:' tag here. > Signed-off-by: Kairui Song <kasong@redhat.com> > --- > fs/proc/vmcore.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > index 3fe90443c1bb..e28695ef2439 100644 > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; > /* Device Dump list and mutex to synchronize access to list */ > static LIST_HEAD(vmcoredd_list); > static DEFINE_MUTEX(vmcoredd_mutex); > + > +/* Device Dump Limit */ > +static size_t vmcoredd_limit; > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > /* Device Dump Size */ > @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > data_size = roundup(sizeof(struct vmcoredd_header) + data->size, > PAGE_SIZE); > > + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { > + ret = -ENOMEM; Should we be adding a WARN() here to let the user know that the device dump data will not be available in vmcore? > + goto out_err; > + } > + > /* Allocate buffer for driver's to write their dumps */ > buf = vmcore_alloc_buf(data_size); > if (!buf) { > @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > return ret; > } > EXPORT_SYMBOL(vmcore_add_device_dump); > + > +static int __init parse_vmcoredd_limit(char *arg) > +{ > + char *end; > + > + if (!arg) > + return -EINVAL; > + vmcoredd_limit = memparse(arg, &end); > + return end > arg ? 0 : -EINVAL; > + > +} > +__setup("device_dump_limit=", parse_vmcoredd_limit); We should be adding this boot argument and its description to 'Documentation/admin-guide/kernel-parameters.txt' > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > /* Free all dumps in vmcore device dump list */ > Thanks, Bhupesh ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-10 11:17 ` Bhupesh Sharma @ 2019-05-16 8:19 ` Kairui Song 2019-05-20 5:55 ` Bhupesh Sharma 0 siblings, 1 reply; 7+ messages in thread From: Kairui Song @ 2019-05-16 8:19 UTC (permalink / raw) To: Bhupesh Sharma Cc: Linux Kernel Mailing List, kexec, David S . Miller, Rahul Lakkireddy, Eric Biederman, Andrew Morton, Dave Young, Alexey Dobriyan, Ganesh Goudar On Fri, May 10, 2019 at 7:17 PM Bhupesh Sharma <bhsharma@redhat.com> wrote: > > Hi Kairui, > > Thanks for the patch. Please see my comments in-line: > > On 05/10/2019 03:50 PM, Kairui Song wrote: > > Device dump allow drivers to add device related dump data to vmcore as > > they want. This have a potential issue, the data is stored in memory, > > drivers may append too much data and use too much memory. The vmcore is > > typically used in a kdump kernel which runs in a pre-reserved small > > chunk of memory. So as a result it will make kdump unusable at all due > > to OOM issues. > > > > So introduce new device_dump_limit= kernel parameter, and set the > > default limit to 0, so device dump is not enabled unless user specify > > the accetable maxiam > > ^^^^ acceptable maximum Will fix this typo. > > > memory usage for device dump data. In this way user > > will also have the chance to adjust the kdump reserved memory > > accordingly. > > Hmmm., this doesn't give much confidence with the > PROC_VMCORE_DEVICE_DUMP feature in its current shape. Rather shouldn't > we be enabling config PROC_VMCORE_DEVICE_DUMP only under EXPERT mode for > now, considering that this feature needs further thrashing and testing > with real setups including platforms where drivers append large amounts > of data to vmcore: I think no need to move it to expert mode, just leave it disabled by default should be better, that should be enough to make sure driver won't append that much memory and cause OOM, while it could still be enabled without changing the kernel, so this feature won't bring extra risk, and could be enabled anytime easily. > > diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig > index 817c02b13b1d..c47a12cf7fc0 100644 > --- a/fs/proc/Kconfig > +++ b/fs/proc/Kconfig > @@ -45,7 +45,7 @@ config PROC_VMCORE > Exports the dump image of crashed kernel in ELF format. > > config PROC_VMCORE_DEVICE_DUMP > - bool "Device Hardware/Firmware Log Collection" > + bool "Device Hardware/Firmware Log Collection" if EXPERT > depends on PROC_VMCORE > default n > help > @@ -59,6 +59,12 @@ config PROC_VMCORE_DEVICE_DUMP > If you say Y here, the collected device dumps will be added > as ELF notes to /proc/vmcore. > > + Considering that there can be device drivers which append > + large amounts of data to vmcore, you should say N here unless > + you are reserving a large chunk of memory for crashdump > + kernel, because otherwise the crashdump kernel might become > + unusable due to OOM issues. > + > > May be you can add a 'Fixes:' tag here. Problem is previous commit seems not broken, just bring extra memory stress. Is "Fixes:" tag suitable for this commit? > > > Signed-off-by: Kairui Song <kasong@redhat.com> > > --- > > fs/proc/vmcore.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > > index 3fe90443c1bb..e28695ef2439 100644 > > --- a/fs/proc/vmcore.c > > +++ b/fs/proc/vmcore.c > > @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; > > /* Device Dump list and mutex to synchronize access to list */ > > static LIST_HEAD(vmcoredd_list); > > static DEFINE_MUTEX(vmcoredd_mutex); > > + > > +/* Device Dump Limit */ > > +static size_t vmcoredd_limit; > > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > > > /* Device Dump Size */ > > @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > > data_size = roundup(sizeof(struct vmcoredd_header) + data->size, > > PAGE_SIZE); > > > > + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { > > + ret = -ENOMEM; > > Should we be adding a WARN() here to let the user know that the device > dump data will not be available in vmcore? Yes, that could be very helpful. How about pr_err_once? WARN is too noise, just give a hint to the user that device dump is disabled should be enough, so user will know why device dump data is not present and will just enable it. > > > + goto out_err; > > + } > > + > > /* Allocate buffer for driver's to write their dumps */ > > buf = vmcore_alloc_buf(data_size); > > if (!buf) { > > @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > > return ret; > > } > > EXPORT_SYMBOL(vmcore_add_device_dump); > > + > > +static int __init parse_vmcoredd_limit(char *arg) > > +{ > > + char *end; > > + > > + if (!arg) > > + return -EINVAL; > > + vmcoredd_limit = memparse(arg, &end); > > + return end > arg ? 0 : -EINVAL; > > + > > +} > > +__setup("device_dump_limit=", parse_vmcoredd_limit); > > We should be adding this boot argument and its description to > 'Documentation/admin-guide/kernel-parameters.txt' Good suggestion, will update the document. > > > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > > > /* Free all dumps in vmcore device dump list */ > > > > Thanks, > Bhupesh Thanks for the review! -- Best Regards, Kairui Song ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-16 8:19 ` Kairui Song @ 2019-05-20 5:55 ` Bhupesh Sharma 2019-05-20 6:20 ` Kairui Song 0 siblings, 1 reply; 7+ messages in thread From: Bhupesh Sharma @ 2019-05-20 5:55 UTC (permalink / raw) To: Kairui Song Cc: Linux Kernel Mailing List, kexec, David S . Miller, Rahul Lakkireddy, Eric Biederman, Andrew Morton, Dave Young, Alexey Dobriyan, Ganesh Goudar On 05/16/2019 01:49 PM, Kairui Song wrote: > On Fri, May 10, 2019 at 7:17 PM Bhupesh Sharma <bhsharma@redhat.com> wrote: >> >> Hi Kairui, >> >> Thanks for the patch. Please see my comments in-line: >> >> On 05/10/2019 03:50 PM, Kairui Song wrote: >>> Device dump allow drivers to add device related dump data to vmcore as >>> they want. This have a potential issue, the data is stored in memory, >>> drivers may append too much data and use too much memory. The vmcore is >>> typically used in a kdump kernel which runs in a pre-reserved small >>> chunk of memory. So as a result it will make kdump unusable at all due >>> to OOM issues. >>> >>> So introduce new device_dump_limit= kernel parameter, and set the >>> default limit to 0, so device dump is not enabled unless user specify >>> the accetable maxiam >> >> ^^^^ acceptable maximum > > Will fix this typo. Ok. >>> memory usage for device dump data. In this way user >>> will also have the chance to adjust the kdump reserved memory >>> accordingly. >> >> Hmmm., this doesn't give much confidence with the >> PROC_VMCORE_DEVICE_DUMP feature in its current shape. Rather shouldn't >> we be enabling config PROC_VMCORE_DEVICE_DUMP only under EXPERT mode for >> now, considering that this feature needs further thrashing and testing >> with real setups including platforms where drivers append large amounts >> of data to vmcore: > > I think no need to move it to expert mode, just leave it disabled by > default should be better, that should be enough to make sure driver > won't append that much memory and cause OOM, while it could still be > enabled without changing the kernel, so this feature won't bring extra > risk, and could be enabled anytime easily. I have seen some arm64 users report issues on mailing lists with PROC_VMCORE_DEVICE_DUMP enabled as this causes frequent OOM in the arm64 crash dump kernel. I think they are using this infrastructure to extend/enable device driver debugging on some arm64 platforms and finding issues with the crash dump kernel. I will do some analysis later-on (when I get some spare time) and post a patch (if needed) to put the same under EXPERT mode for now. >> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig >> index 817c02b13b1d..c47a12cf7fc0 100644 >> --- a/fs/proc/Kconfig >> +++ b/fs/proc/Kconfig >> @@ -45,7 +45,7 @@ config PROC_VMCORE >> Exports the dump image of crashed kernel in ELF format. >> >> config PROC_VMCORE_DEVICE_DUMP >> - bool "Device Hardware/Firmware Log Collection" >> + bool "Device Hardware/Firmware Log Collection" if EXPERT >> depends on PROC_VMCORE >> default n >> help >> @@ -59,6 +59,12 @@ config PROC_VMCORE_DEVICE_DUMP >> If you say Y here, the collected device dumps will be added >> as ELF notes to /proc/vmcore. >> >> + Considering that there can be device drivers which append >> + large amounts of data to vmcore, you should say N here unless >> + you are reserving a large chunk of memory for crashdump >> + kernel, because otherwise the crashdump kernel might become >> + unusable due to OOM issues. >> + >> >> May be you can add a 'Fixes:' tag here. > > Problem is previous commit seems not broken, just bring extra memory > stress. Is "Fixes:" tag suitable for this commit? I think since the earlier patch causes an OOM, it would be better to atleast mention it in the git log (for easier git bisect later on). If not the 'Fixes:' tag may be we can use a 'Since commit ..' like wording in the commit log. >>> Signed-off-by: Kairui Song <kasong@redhat.com> >>> --- >>> fs/proc/vmcore.c | 20 ++++++++++++++++++++ >>> 1 file changed, 20 insertions(+) >>> >>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c >>> index 3fe90443c1bb..e28695ef2439 100644 >>> --- a/fs/proc/vmcore.c >>> +++ b/fs/proc/vmcore.c >>> @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; >>> /* Device Dump list and mutex to synchronize access to list */ >>> static LIST_HEAD(vmcoredd_list); >>> static DEFINE_MUTEX(vmcoredd_mutex); >>> + >>> +/* Device Dump Limit */ >>> +static size_t vmcoredd_limit; >>> #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ >>> >>> /* Device Dump Size */ >>> @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) >>> data_size = roundup(sizeof(struct vmcoredd_header) + data->size, >>> PAGE_SIZE); >>> >>> + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { >>> + ret = -ENOMEM; >> >> Should we be adding a WARN() here to let the user know that the device >> dump data will not be available in vmcore? > > Yes, that could be very helpful. How about pr_err_once? WARN is too > noise, just give a hint to the user that device dump is disabled > should be enough, so user will know why device dump data is not > present and will just enable it. Sure, pr_err() should be OK as well. >>> + goto out_err; >>> + } >>> + >>> /* Allocate buffer for driver's to write their dumps */ >>> buf = vmcore_alloc_buf(data_size); >>> if (!buf) { >>> @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) >>> return ret; >>> } >>> EXPORT_SYMBOL(vmcore_add_device_dump); >>> + >>> +static int __init parse_vmcoredd_limit(char *arg) >>> +{ >>> + char *end; >>> + >>> + if (!arg) >>> + return -EINVAL; >>> + vmcoredd_limit = memparse(arg, &end); >>> + return end > arg ? 0 : -EINVAL; >>> + >>> +} >>> +__setup("device_dump_limit=", parse_vmcoredd_limit); >> >> We should be adding this boot argument and its description to >> 'Documentation/admin-guide/kernel-parameters.txt' > > Good suggestion, will update the document. > >> >>> #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ >>> >>> /* Free all dumps in vmcore device dump list */ >>> Thanks, Bhupesh ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-20 5:55 ` Bhupesh Sharma @ 2019-05-20 6:20 ` Kairui Song 0 siblings, 0 replies; 7+ messages in thread From: Kairui Song @ 2019-05-20 6:20 UTC (permalink / raw) To: Bhupesh Sharma Cc: Linux Kernel Mailing List, kexec, David S . Miller, Rahul Lakkireddy, Eric Biederman, Andrew Morton, Dave Young, Alexey Dobriyan, Ganesh Goudar On Mon, May 20, 2019 at 1:55 PM Bhupesh Sharma <bhsharma@redhat.com> wrote: > > On 05/16/2019 01:49 PM, Kairui Song wrote: > > On Fri, May 10, 2019 at 7:17 PM Bhupesh Sharma <bhsharma@redhat.com> wrote: > >> > >> Hi Kairui, > >> > >> Thanks for the patch. Please see my comments in-line: > >> > >> On 05/10/2019 03:50 PM, Kairui Song wrote: > >>> Device dump allow drivers to add device related dump data to vmcore as > >>> they want. This have a potential issue, the data is stored in memory, > >>> drivers may append too much data and use too much memory. The vmcore is > >>> typically used in a kdump kernel which runs in a pre-reserved small > >>> chunk of memory. So as a result it will make kdump unusable at all due > >>> to OOM issues. > >>> > >>> So introduce new device_dump_limit= kernel parameter, and set the > >>> default limit to 0, so device dump is not enabled unless user specify > >>> the accetable maxiam > >> > >> ^^^^ acceptable maximum > > > > Will fix this typo. > > Ok. > > >>> memory usage for device dump data. In this way user > >>> will also have the chance to adjust the kdump reserved memory > >>> accordingly. > >> > >> Hmmm., this doesn't give much confidence with the > >> PROC_VMCORE_DEVICE_DUMP feature in its current shape. Rather shouldn't > >> we be enabling config PROC_VMCORE_DEVICE_DUMP only under EXPERT mode for > >> now, considering that this feature needs further thrashing and testing > >> with real setups including platforms where drivers append large amounts > >> of data to vmcore: > > > > I think no need to move it to expert mode, just leave it disabled by > > default should be better, that should be enough to make sure driver > > won't append that much memory and cause OOM, while it could still be > > enabled without changing the kernel, so this feature won't bring extra > > risk, and could be enabled anytime easily. > > I have seen some arm64 users report issues on mailing lists with > PROC_VMCORE_DEVICE_DUMP enabled as this causes frequent OOM in the arm64 > crash dump kernel. > > I think they are using this infrastructure to extend/enable device > driver debugging on some arm64 platforms and finding issues with the > crash dump kernel. > > I will do some analysis later-on (when I get some spare time) and post a > patch (if needed) to put the same under EXPERT mode for now. > > >> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig > >> index 817c02b13b1d..c47a12cf7fc0 100644 > >> --- a/fs/proc/Kconfig > >> +++ b/fs/proc/Kconfig > >> @@ -45,7 +45,7 @@ config PROC_VMCORE > >> Exports the dump image of crashed kernel in ELF format. > >> > >> config PROC_VMCORE_DEVICE_DUMP > >> - bool "Device Hardware/Firmware Log Collection" > >> + bool "Device Hardware/Firmware Log Collection" if EXPERT > >> depends on PROC_VMCORE > >> default n > >> help > >> @@ -59,6 +59,12 @@ config PROC_VMCORE_DEVICE_DUMP > >> If you say Y here, the collected device dumps will be added > >> as ELF notes to /proc/vmcore. > >> > >> + Considering that there can be device drivers which append > >> + large amounts of data to vmcore, you should say N here unless > >> + you are reserving a large chunk of memory for crashdump > >> + kernel, because otherwise the crashdump kernel might become > >> + unusable due to OOM issues. > >> + > >> > >> May be you can add a 'Fixes:' tag here. > > > > Problem is previous commit seems not broken, just bring extra memory > > stress. Is "Fixes:" tag suitable for this commit? > > I think since the earlier patch causes an OOM, it would be better to > atleast mention it in the git log (for easier git bisect later on). > > If not the 'Fixes:' tag may be we can use a 'Since commit ..' like > wording in the commit log. > > >>> Signed-off-by: Kairui Song <kasong@redhat.com> > >>> --- > >>> fs/proc/vmcore.c | 20 ++++++++++++++++++++ > >>> 1 file changed, 20 insertions(+) > >>> > >>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > >>> index 3fe90443c1bb..e28695ef2439 100644 > >>> --- a/fs/proc/vmcore.c > >>> +++ b/fs/proc/vmcore.c > >>> @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; > >>> /* Device Dump list and mutex to synchronize access to list */ > >>> static LIST_HEAD(vmcoredd_list); > >>> static DEFINE_MUTEX(vmcoredd_mutex); > >>> + > >>> +/* Device Dump Limit */ > >>> +static size_t vmcoredd_limit; > >>> #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > >>> > >>> /* Device Dump Size */ > >>> @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > >>> data_size = roundup(sizeof(struct vmcoredd_header) + data->size, > >>> PAGE_SIZE); > >>> > >>> + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { > >>> + ret = -ENOMEM; > >> > >> Should we be adding a WARN() here to let the user know that the device > >> dump data will not be available in vmcore? > > > > Yes, that could be very helpful. How about pr_err_once? WARN is too > > noise, just give a hint to the user that device dump is disabled > > should be enough, so user will know why device dump data is not > > present and will just enable it. > > Sure, pr_err() should be OK as well. > > >>> + goto out_err; > >>> + } > >>> + > >>> /* Allocate buffer for driver's to write their dumps */ > >>> buf = vmcore_alloc_buf(data_size); > >>> if (!buf) { > >>> @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > >>> return ret; > >>> } > >>> EXPORT_SYMBOL(vmcore_add_device_dump); > >>> + > >>> +static int __init parse_vmcoredd_limit(char *arg) > >>> +{ > >>> + char *end; > >>> + > >>> + if (!arg) > >>> + return -EINVAL; > >>> + vmcoredd_limit = memparse(arg, &end); > >>> + return end > arg ? 0 : -EINVAL; > >>> + > >>> +} > >>> +__setup("device_dump_limit=", parse_vmcoredd_limit); > >> > >> We should be adding this boot argument and its description to > >> 'Documentation/admin-guide/kernel-parameters.txt' > > > > Good suggestion, will update the document. > > > >> > >>> #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > >>> > >>> /* Free all dumps in vmcore device dump list */ > >>> > > Thanks, > Bhupesh Thanks for the reply, I've updated the patch accordingly and sent V2. -- Best Regards, Kairui Song ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-10 10:20 [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit Kairui Song 2019-05-10 11:17 ` Bhupesh Sharma @ 2019-05-13 1:52 ` Dave Young 2019-05-13 2:19 ` Kairui Song 1 sibling, 1 reply; 7+ messages in thread From: Dave Young @ 2019-05-13 1:52 UTC (permalink / raw) To: Kairui Song Cc: linux-kernel, Rahul Lakkireddy, Ganesh Goudar, David S . Miller, Eric Biederman, Alexey Dobriyan, Andrew Morton, kexec On 05/10/19 at 06:20pm, Kairui Song wrote: > Device dump allow drivers to add device related dump data to vmcore as > they want. This have a potential issue, the data is stored in memory, > drivers may append too much data and use too much memory. The vmcore is > typically used in a kdump kernel which runs in a pre-reserved small > chunk of memory. So as a result it will make kdump unusable at all due > to OOM issues. > > So introduce new device_dump_limit= kernel parameter, and set the > default limit to 0, so device dump is not enabled unless user specify > the accetable maxiam memory usage for device dump data. In this way user > will also have the chance to adjust the kdump reserved memory > accordingly. The device dump is only affective in kdump 2nd kernel, so add the limitation seems not useful. One is hard to know the correct size unless one does some crash test. If one did the test and want to eanble the device dump he needs increase crashkernel= size in 1st kernel and add the limit param in 2nd kernel. So a global on/off param sounds easier and better, something like vmcore_device_dump=on (default is off) > > Signed-off-by: Kairui Song <kasong@redhat.com> > --- > fs/proc/vmcore.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > index 3fe90443c1bb..e28695ef2439 100644 > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; > /* Device Dump list and mutex to synchronize access to list */ > static LIST_HEAD(vmcoredd_list); > static DEFINE_MUTEX(vmcoredd_mutex); > + > +/* Device Dump Limit */ > +static size_t vmcoredd_limit; > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > /* Device Dump Size */ > @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > data_size = roundup(sizeof(struct vmcoredd_header) + data->size, > PAGE_SIZE); > > + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { > + ret = -ENOMEM; > + goto out_err; > + } > + > /* Allocate buffer for driver's to write their dumps */ > buf = vmcore_alloc_buf(data_size); > if (!buf) { > @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > return ret; > } > EXPORT_SYMBOL(vmcore_add_device_dump); > + > +static int __init parse_vmcoredd_limit(char *arg) > +{ > + char *end; > + > + if (!arg) > + return -EINVAL; > + vmcoredd_limit = memparse(arg, &end); > + return end > arg ? 0 : -EINVAL; > + > +} > +__setup("device_dump_limit=", parse_vmcoredd_limit); > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > /* Free all dumps in vmcore device dump list */ > -- > 2.20.1 > Thanks Dave ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit 2019-05-13 1:52 ` Dave Young @ 2019-05-13 2:19 ` Kairui Song 0 siblings, 0 replies; 7+ messages in thread From: Kairui Song @ 2019-05-13 2:19 UTC (permalink / raw) To: Dave Young Cc: Linux Kernel Mailing List, Rahul Lakkireddy, Ganesh Goudar, David S . Miller, Eric Biederman, Alexey Dobriyan, Andrew Morton, kexec, Bhupesh Sharma On Mon, May 13, 2019 at 9:52 AM Dave Young <dyoung@redhat.com> wrote: > > On 05/10/19 at 06:20pm, Kairui Song wrote: > > Device dump allow drivers to add device related dump data to vmcore as > > they want. This have a potential issue, the data is stored in memory, > > drivers may append too much data and use too much memory. The vmcore is > > typically used in a kdump kernel which runs in a pre-reserved small > > chunk of memory. So as a result it will make kdump unusable at all due > > to OOM issues. > > > > So introduce new device_dump_limit= kernel parameter, and set the > > default limit to 0, so device dump is not enabled unless user specify > > the accetable maxiam memory usage for device dump data. In this way user > > will also have the chance to adjust the kdump reserved memory > > accordingly. > > The device dump is only affective in kdump 2nd kernel, so add the > limitation seems not useful. One is hard to know the correct size > unless one does some crash test. If one did the test and want to eanble > the device dump he needs increase crashkernel= size in 1st kernel and > add the limit param in 2nd kernel. > > So a global on/off param sounds easier and better, something like > vmcore_device_dump=on (default is off) Yes, on/off could be another way to solve this issue, the size limit could being more flexibility, if device dump is not asking for too much memory then it would just work but bring extra complexity indeed. Considering it's actually hard to know how much memory is needed for the device dump drivers to work, I'll update to use the on/off cmdline then. > > > > > Signed-off-by: Kairui Song <kasong@redhat.com> > > --- > > fs/proc/vmcore.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > > index 3fe90443c1bb..e28695ef2439 100644 > > --- a/fs/proc/vmcore.c > > +++ b/fs/proc/vmcore.c > > @@ -53,6 +53,9 @@ static struct proc_dir_entry *proc_vmcore; > > /* Device Dump list and mutex to synchronize access to list */ > > static LIST_HEAD(vmcoredd_list); > > static DEFINE_MUTEX(vmcoredd_mutex); > > + > > +/* Device Dump Limit */ > > +static size_t vmcoredd_limit; > > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > > > /* Device Dump Size */ > > @@ -1465,6 +1468,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > > data_size = roundup(sizeof(struct vmcoredd_header) + data->size, > > PAGE_SIZE); > > > > + if (vmcoredd_orig_sz + data_size >= vmcoredd_limit) { > > + ret = -ENOMEM; > > + goto out_err; > > + } > > + > > /* Allocate buffer for driver's to write their dumps */ > > buf = vmcore_alloc_buf(data_size); > > if (!buf) { > > @@ -1502,6 +1510,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) > > return ret; > > } > > EXPORT_SYMBOL(vmcore_add_device_dump); > > + > > +static int __init parse_vmcoredd_limit(char *arg) > > +{ > > + char *end; > > + > > + if (!arg) > > + return -EINVAL; > > + vmcoredd_limit = memparse(arg, &end); > > + return end > arg ? 0 : -EINVAL; > > + > > +} > > +__setup("device_dump_limit=", parse_vmcoredd_limit); > > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ > > > > /* Free all dumps in vmcore device dump list */ > > -- > > 2.20.1 > > > > Thanks > Dave -- Best Regards, Kairui Song ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2019-05-20 6:21 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-05-10 10:20 [RFC PATCH] vmcore: Add a kernel cmdline device_dump_limit Kairui Song 2019-05-10 11:17 ` Bhupesh Sharma 2019-05-16 8:19 ` Kairui Song 2019-05-20 5:55 ` Bhupesh Sharma 2019-05-20 6:20 ` Kairui Song 2019-05-13 1:52 ` Dave Young 2019-05-13 2:19 ` Kairui Song
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