| Message ID | 20190501191846.12634-3-pasha.tatashin@soleen.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | "Hotremove" persistent memory | expand |
On 01.05.19 21:18, Pavel Tatashin wrote: > It is now allowed to use persistent memory like a regular RAM, but > currently there is no way to remove this memory until machine is > rebooted. > > This work expands the functionality to also allows hotremoving > previously hotplugged persistent memory, and recover the device for use > for other purposes. > > To hotremove persistent memory, the management software must first > offline all memory blocks of dax region, and than unbind it from > device-dax/kmem driver. So, operations should look like this: > > echo offline > echo offline > /sys/devices/system/memory/memoryN/state > ... > echo dax0.0 > /sys/bus/dax/drivers/kmem/unbind > > Note: if unbind is done without offlining memory beforehand, it won't be > possible to do dax0.0 hotremove, and dax's memory is going to be part of > System RAM until reboot. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> > --- > drivers/dax/dax-private.h | 2 + > drivers/dax/kmem.c | 99 +++++++++++++++++++++++++++++++++++++-- > 2 files changed, 97 insertions(+), 4 deletions(-) > > diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h > index a45612148ca0..999aaf3a29b3 100644 > --- a/drivers/dax/dax-private.h > +++ b/drivers/dax/dax-private.h > @@ -53,6 +53,7 @@ struct dax_region { > * @pgmap - pgmap for memmap setup / lifetime (driver owned) > * @ref: pgmap reference count (driver owned) > * @cmp: @ref final put completion (driver owned) > + * @dax_mem_res: physical address range of hotadded DAX memory > */ > struct dev_dax { > struct dax_region *region; > @@ -62,6 +63,7 @@ struct dev_dax { > struct dev_pagemap pgmap; > struct percpu_ref ref; > struct completion cmp; > + struct resource *dax_kmem_res; > }; > > static inline struct dev_dax *to_dev_dax(struct device *dev) > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index 4c0131857133..72b868066026 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -71,21 +71,112 @@ int dev_dax_kmem_probe(struct device *dev) > kfree(new_res); > return rc; > } > + dev_dax->dax_kmem_res = new_res; > > return 0; > } > > +#ifdef CONFIG_MEMORY_HOTREMOVE > +static int > +check_devdax_mem_offlined_cb(struct memory_block *mem, void *arg) > +{ > + /* Memory block device */ > + struct device *mem_dev = &mem->dev; > + bool is_offline; > + > + device_lock(mem_dev); > + is_offline = mem_dev->offline; > + device_unlock(mem_dev); > + > + /* > + * Check that device-dax's memory_blocks are offline. If a memory_block > + * is not offline a warning is printed and an error is returned. > + */ > + if (!is_offline) { > + /* Dax device device */ > + struct device *dev = (struct device *)arg; > + struct dev_dax *dev_dax = to_dev_dax(dev); > + struct resource *res = &dev_dax->region->res; > + unsigned long spfn = section_nr_to_pfn(mem->start_section_nr); > + unsigned long epfn = section_nr_to_pfn(mem->end_section_nr) + > + PAGES_PER_SECTION - 1; > + phys_addr_t spa = spfn << PAGE_SHIFT; > + phys_addr_t epa = epfn << PAGE_SHIFT; > + > + dev_err(dev, > + "DAX region %pR cannot be hotremoved until the next reboot. Memory block [%pa-%pa] is not offline.\n", > + res, &spa, &epa); > + > + return -EBUSY; > + } > + > + return 0; > +} > + > +static int dev_dax_kmem_remove(struct device *dev) > +{ > + struct dev_dax *dev_dax = to_dev_dax(dev); > + struct resource *res = dev_dax->dax_kmem_res; > + resource_size_t kmem_start; > + resource_size_t kmem_size; > + unsigned long start_pfn; > + unsigned long end_pfn; > + int rc; > + > + kmem_start = res->start; > + kmem_size = resource_size(res); > + start_pfn = kmem_start >> PAGE_SHIFT; > + end_pfn = start_pfn + (kmem_size >> PAGE_SHIFT) - 1; > + > + /* > + * Keep hotplug lock while checking memory state, and also required > + * during __remove_memory() call. Admin can't change memory state via > + * sysfs while this lock is kept. > + */ > + lock_device_hotplug(); > + > + /* > + * Walk and check that every singe memory_block of dax region is > + * offline. Hotremove can succeed only when every memory_block is > + * offlined beforehand. > + */ > + rc = walk_memory_range(start_pfn, end_pfn, dev, > + check_devdax_mem_offlined_cb); > + > + /* > + * If admin has not offlined memory beforehand, we cannot hotremove dax. > + * Unfortunately, because unbind will still succeed there is no way for > + * user to hotremove dax after this. > + */ > + if (rc) { > + unlock_device_hotplug(); > + return rc; > + } > + > + /* Hotremove memory, cannot fail because memory is already offlined */ > + __remove_memory(dev_dax->target_node, kmem_start, kmem_size); > + unlock_device_hotplug(); > + > + /* Release and free dax resources */ > + release_resource(res); > + kfree(res); > + dev_dax->dax_kmem_res = NULL; > + > + return 0; > +} > +#else > static int dev_dax_kmem_remove(struct device *dev) > { > /* > - * Purposely leak the request_mem_region() for the device-dax > - * range and return '0' to ->remove() attempts. The removal of > - * the device from the driver always succeeds, but the region > - * is permanently pinned as reserved by the unreleased > + * Without hotremove purposely leak the request_mem_region() for the > + * device-dax range and return '0' to ->remove() attempts. The removal > + * of the device from the driver always succeeds, but the region is > + * permanently pinned as reserved by the unreleased > * request_mem_region(). > */ > return 0; > } > +#endif /* CONFIG_MEMORY_HOTREMOVE */ > > static struct dax_device_driver device_dax_kmem_driver = { > .drv = { > Memory unplug bits Reviewed-by: David Hildenbrand <david@redhat.com>
> > Memory unplug bits > > Reviewed-by: David Hildenbrand <david@redhat.com> > Thank you David. Pasha
On Wed, May 1, 2019 at 12:19 PM Pavel Tatashin <pasha.tatashin@soleen.com> wrote: > > It is now allowed to use persistent memory like a regular RAM, but > currently there is no way to remove this memory until machine is > rebooted. > > This work expands the functionality to also allows hotremoving > previously hotplugged persistent memory, and recover the device for use > for other purposes. > > To hotremove persistent memory, the management software must first > offline all memory blocks of dax region, and than unbind it from > device-dax/kmem driver. So, operations should look like this: > > echo offline > echo offline > /sys/devices/system/memory/memoryN/state > ... > echo dax0.0 > /sys/bus/dax/drivers/kmem/unbind > > Note: if unbind is done without offlining memory beforehand, it won't be > possible to do dax0.0 hotremove, and dax's memory is going to be part of > System RAM until reboot. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> > --- > drivers/dax/dax-private.h | 2 + > drivers/dax/kmem.c | 99 +++++++++++++++++++++++++++++++++++++-- > 2 files changed, 97 insertions(+), 4 deletions(-) > > diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h > index a45612148ca0..999aaf3a29b3 100644 > --- a/drivers/dax/dax-private.h > +++ b/drivers/dax/dax-private.h > @@ -53,6 +53,7 @@ struct dax_region { > * @pgmap - pgmap for memmap setup / lifetime (driver owned) > * @ref: pgmap reference count (driver owned) > * @cmp: @ref final put completion (driver owned) > + * @dax_mem_res: physical address range of hotadded DAX memory > */ > struct dev_dax { > struct dax_region *region; > @@ -62,6 +63,7 @@ struct dev_dax { > struct dev_pagemap pgmap; > struct percpu_ref ref; > struct completion cmp; > + struct resource *dax_kmem_res; > }; > > static inline struct dev_dax *to_dev_dax(struct device *dev) > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index 4c0131857133..72b868066026 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -71,21 +71,112 @@ int dev_dax_kmem_probe(struct device *dev) > kfree(new_res); > return rc; > } > + dev_dax->dax_kmem_res = new_res; > > return 0; > } > > +#ifdef CONFIG_MEMORY_HOTREMOVE > +static int > +check_devdax_mem_offlined_cb(struct memory_block *mem, void *arg) > +{ > + /* Memory block device */ > + struct device *mem_dev = &mem->dev; > + bool is_offline; > + > + device_lock(mem_dev); > + is_offline = mem_dev->offline; > + device_unlock(mem_dev); > + > + /* > + * Check that device-dax's memory_blocks are offline. If a memory_block > + * is not offline a warning is printed and an error is returned. > + */ > + if (!is_offline) { > + /* Dax device device */ > + struct device *dev = (struct device *)arg; > + struct dev_dax *dev_dax = to_dev_dax(dev); > + struct resource *res = &dev_dax->region->res; > + unsigned long spfn = section_nr_to_pfn(mem->start_section_nr); > + unsigned long epfn = section_nr_to_pfn(mem->end_section_nr) + > + PAGES_PER_SECTION - 1; > + phys_addr_t spa = spfn << PAGE_SHIFT; > + phys_addr_t epa = epfn << PAGE_SHIFT; > + > + dev_err(dev, > + "DAX region %pR cannot be hotremoved until the next reboot. Memory block [%pa-%pa] is not offline.\n", > + res, &spa, &epa); > + > + return -EBUSY; > + } > + > + return 0; > +} > + > +static int dev_dax_kmem_remove(struct device *dev) > +{ > + struct dev_dax *dev_dax = to_dev_dax(dev); > + struct resource *res = dev_dax->dax_kmem_res; > + resource_size_t kmem_start; > + resource_size_t kmem_size; > + unsigned long start_pfn; > + unsigned long end_pfn; > + int rc; > + > + kmem_start = res->start; > + kmem_size = resource_size(res); > + start_pfn = kmem_start >> PAGE_SHIFT; > + end_pfn = start_pfn + (kmem_size >> PAGE_SHIFT) - 1; > + > + /* > + * Keep hotplug lock while checking memory state, and also required > + * during __remove_memory() call. Admin can't change memory state via > + * sysfs while this lock is kept. > + */ > + lock_device_hotplug(); > + > + /* > + * Walk and check that every singe memory_block of dax region is > + * offline. Hotremove can succeed only when every memory_block is > + * offlined beforehand. > + */ > + rc = walk_memory_range(start_pfn, end_pfn, dev, > + check_devdax_mem_offlined_cb); > + > + /* > + * If admin has not offlined memory beforehand, we cannot hotremove dax. > + * Unfortunately, because unbind will still succeed there is no way for > + * user to hotremove dax after this. > + */ > + if (rc) { > + unlock_device_hotplug(); > + return rc; > + } > + > + /* Hotremove memory, cannot fail because memory is already offlined */ > + __remove_memory(dev_dax->target_node, kmem_start, kmem_size); > + unlock_device_hotplug(); Currently the kmem driver can be built as a module, and I don't see a need to drop that flexibility. What about wrapping these core routines: unlock_device_hotplug __remove_memory walk_memory_range lock_device_hotplug ...into a common exported (gpl) helper like: int try_remove_memory(int nid, struct resource *res) Because as far as I can see there's nothing device-dax specific about this "try remove iff offline" functionality outside of looking up the related 'struct resource'. The check_devdax_mem_offlined_cb callback can be made generic if the callback argument is the resource pointer.
> Currently the kmem driver can be built as a module, and I don't see a > need to drop that flexibility. What about wrapping these core > routines: > > unlock_device_hotplug > __remove_memory > walk_memory_range > lock_device_hotplug > > ...into a common exported (gpl) helper like: > > int try_remove_memory(int nid, struct resource *res) > > Because as far as I can see there's nothing device-dax specific about > this "try remove iff offline" functionality outside of looking up the > related 'struct resource'. The check_devdax_mem_offlined_cb callback > can be made generic if the callback argument is the resource pointer. Makes sense, I will do both things that you suggested. Thank you, Pasha
On Wed, May 01, 2019 at 03:18:46PM -0400, Pavel Tatashin wrote: >It is now allowed to use persistent memory like a regular RAM, but >currently there is no way to remove this memory until machine is >rebooted. > >This work expands the functionality to also allows hotremoving >previously hotplugged persistent memory, and recover the device for use >for other purposes. > >To hotremove persistent memory, the management software must first >offline all memory blocks of dax region, and than unbind it from >device-dax/kmem driver. So, operations should look like this: > >echo offline > echo offline > /sys/devices/system/memory/memoryN/state This looks wrong :) -- Thanks, Sasha
> >device-dax/kmem driver. So, operations should look like this: > > > >echo offline > echo offline > /sys/devices/system/memory/memoryN/state > > This looks wrong :) > Indeed, I will fix patch log in the next version. Thank you, Pasha
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h index a45612148ca0..999aaf3a29b3 100644 --- a/drivers/dax/dax-private.h +++ b/drivers/dax/dax-private.h @@ -53,6 +53,7 @@ struct dax_region { * @pgmap - pgmap for memmap setup / lifetime (driver owned) * @ref: pgmap reference count (driver owned) * @cmp: @ref final put completion (driver owned) + * @dax_mem_res: physical address range of hotadded DAX memory */ struct dev_dax { struct dax_region *region; @@ -62,6 +63,7 @@ struct dev_dax { struct dev_pagemap pgmap; struct percpu_ref ref; struct completion cmp; + struct resource *dax_kmem_res; }; static inline struct dev_dax *to_dev_dax(struct device *dev) diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c index 4c0131857133..72b868066026 100644 --- a/drivers/dax/kmem.c +++ b/drivers/dax/kmem.c @@ -71,21 +71,112 @@ int dev_dax_kmem_probe(struct device *dev) kfree(new_res); return rc; } + dev_dax->dax_kmem_res = new_res; return 0; } +#ifdef CONFIG_MEMORY_HOTREMOVE +static int +check_devdax_mem_offlined_cb(struct memory_block *mem, void *arg) +{ + /* Memory block device */ + struct device *mem_dev = &mem->dev; + bool is_offline; + + device_lock(mem_dev); + is_offline = mem_dev->offline; + device_unlock(mem_dev); + + /* + * Check that device-dax's memory_blocks are offline. If a memory_block + * is not offline a warning is printed and an error is returned. + */ + if (!is_offline) { + /* Dax device device */ + struct device *dev = (struct device *)arg; + struct dev_dax *dev_dax = to_dev_dax(dev); + struct resource *res = &dev_dax->region->res; + unsigned long spfn = section_nr_to_pfn(mem->start_section_nr); + unsigned long epfn = section_nr_to_pfn(mem->end_section_nr) + + PAGES_PER_SECTION - 1; + phys_addr_t spa = spfn << PAGE_SHIFT; + phys_addr_t epa = epfn << PAGE_SHIFT; + + dev_err(dev, + "DAX region %pR cannot be hotremoved until the next reboot. Memory block [%pa-%pa] is not offline.\n", + res, &spa, &epa); + + return -EBUSY; + } + + return 0; +} + +static int dev_dax_kmem_remove(struct device *dev) +{ + struct dev_dax *dev_dax = to_dev_dax(dev); + struct resource *res = dev_dax->dax_kmem_res; + resource_size_t kmem_start; + resource_size_t kmem_size; + unsigned long start_pfn; + unsigned long end_pfn; + int rc; + + kmem_start = res->start; + kmem_size = resource_size(res); + start_pfn = kmem_start >> PAGE_SHIFT; + end_pfn = start_pfn + (kmem_size >> PAGE_SHIFT) - 1; + + /* + * Keep hotplug lock while checking memory state, and also required + * during __remove_memory() call. Admin can't change memory state via + * sysfs while this lock is kept. + */ + lock_device_hotplug(); + + /* + * Walk and check that every singe memory_block of dax region is + * offline. Hotremove can succeed only when every memory_block is + * offlined beforehand. + */ + rc = walk_memory_range(start_pfn, end_pfn, dev, + check_devdax_mem_offlined_cb); + + /* + * If admin has not offlined memory beforehand, we cannot hotremove dax. + * Unfortunately, because unbind will still succeed there is no way for + * user to hotremove dax after this. + */ + if (rc) { + unlock_device_hotplug(); + return rc; + } + + /* Hotremove memory, cannot fail because memory is already offlined */ + __remove_memory(dev_dax->target_node, kmem_start, kmem_size); + unlock_device_hotplug(); + + /* Release and free dax resources */ + release_resource(res); + kfree(res); + dev_dax->dax_kmem_res = NULL; + + return 0; +} +#else static int dev_dax_kmem_remove(struct device *dev) { /* - * Purposely leak the request_mem_region() for the device-dax - * range and return '0' to ->remove() attempts. The removal of - * the device from the driver always succeeds, but the region - * is permanently pinned as reserved by the unreleased + * Without hotremove purposely leak the request_mem_region() for the + * device-dax range and return '0' to ->remove() attempts. The removal + * of the device from the driver always succeeds, but the region is + * permanently pinned as reserved by the unreleased * request_mem_region(). */ return 0; } +#endif /* CONFIG_MEMORY_HOTREMOVE */ static struct dax_device_driver device_dax_kmem_driver = { .drv = {
It is now allowed to use persistent memory like a regular RAM, but currently there is no way to remove this memory until machine is rebooted. This work expands the functionality to also allows hotremoving previously hotplugged persistent memory, and recover the device for use for other purposes. To hotremove persistent memory, the management software must first offline all memory blocks of dax region, and than unbind it from device-dax/kmem driver. So, operations should look like this: echo offline > echo offline > /sys/devices/system/memory/memoryN/state ... echo dax0.0 > /sys/bus/dax/drivers/kmem/unbind Note: if unbind is done without offlining memory beforehand, it won't be possible to do dax0.0 hotremove, and dax's memory is going to be part of System RAM until reboot. Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> --- drivers/dax/dax-private.h | 2 + drivers/dax/kmem.c | 99 +++++++++++++++++++++++++++++++++++++-- 2 files changed, 97 insertions(+), 4 deletions(-)