linux/drivers/base/memory.c, branch v4.1

mm, hotplug: fix concurrent memory hot-add deadlock

2015-04-14T23:49:00Z

There's a deadlock when concurrently hot-adding memory through the probe interface and switching a memory block from offline to online. When hot-adding memory via the probe interface, add_memory() first takes mem_hotplug_begin() and then device_lock() is later taken when registering the newly initialized memory block. This creates a lock dependency of (1) mem_hotplug.lock (2) dev->mutex. When switching a memory block from offline to online, dev->mutex is first grabbed in device_online() when the write(2) transitions an existing memory block from offline to online, and then online_pages() will take mem_hotplug_begin(). This creates a lock inversion between mem_hotplug.lock and dev->mutex. Vitaly reports that this deadlock can happen when kworker handling a probe event races with systemd-udevd switching a memory block's state. This patch requires the state transition to take mem_hotplug_begin() before dev->mutex. Hot-adding memory via the probe interface creates a memory block while holding mem_hotplug_begin(), there is no way to take dev->mutex first in this case. online_pages() and offline_pages() are only called when transitioning memory block state. We now require that mem_hotplug_begin() is taken before calling them -- this requires exporting the mem_hotplug_begin() and mem_hotplug_done() to generic code. In all hot-add and hot-remove cases, mem_hotplug_begin() is done prior to device_online(). This is all that is needed to avoid the deadlock. Signed-off-by: David Rientjes Reported-by: Vitaly Kuznetsov Tested-by: Vitaly Kuznetsov Cc: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Cc: "K. Y. Srinivasan" Cc: Yasuaki Ishimatsu Cc: Tang Chen Cc: Vlastimil Babka Cc: Zhang Zhen Cc: Vladimir Davydov Cc: Wang Nan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory hotplug: use macro to switch between section and pfn

2015-04-14T23:49:00Z

Use macro section_nr_to_pfn() to switch between section and pfn, instead of open-coding it. No semantic changes. Signed-off-by: Sheng Yong Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

drivers: base: memory: Use tabs instead of spaces

2015-03-25T13:36:20Z

This patch changes spaces to tabs. Found using checkpatch.pl Signed-off-by: Ioana Ciornei Signed-off-by: Greg Kroah-Hartman

drivers: base: memory: Fix switch indent

2015-03-25T13:35:08Z

Signed-off-by: Ioana Ciornei Signed-off-by: Greg Kroah-Hartman

memory-hotplug: remove redundant call of page_to_pfn

2014-12-13T20:42:47Z

This is just a small optimization. The start_pfn can be obtained directly by phys_index << PFN_SECTION_SHIFT. So the call of page_to_pfn() is redundant and remove it. Signed-off-by: Zhang Zhen Acked-by: Yasuaki Ishimatsu Acked-by: David Rientjes Cc: Dave Hansen Cc: Wang Nan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory-hotplug: add sysfs valid_zones attribute

2014-10-10T02:25:52Z

Currently memory-hotplug has two limits: 1. If the memory block is in ZONE_NORMAL, you can change it to ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE. 2. If the memory block is in ZONE_MOVABLE, you can change it to ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL. With this patch, we can easy to know a memory block can be onlined to which zone, and don't need to know the above two limits. Updated the related Documentation. [akpm@linux-foundation.org: use conventional comment layout] [akpm@linux-foundation.org: fix build with CONFIG_MEMORY_HOTREMOVE=n] [akpm@linux-foundation.org: remove unused local zone_prev] Signed-off-by: Zhang Zhen Cc: Dave Hansen Cc: David Rientjes Cc: Toshi Kani Cc: Yasuaki Ishimatsu Cc: Naoya Horiguchi Cc: Wang Nan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/mem-hotplug: replace simple_strtoull() with kstrtoull()

2014-08-07T01:01:18Z

Use the newer and more pleasant kstrtoull() to replace simple_strtoull(), because simple_strtoull() is marked for obsoletion. Signed-off-by: Zhang Zhen Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mem-hotplug: introduce MMOP_OFFLINE to replace the hard coding -1

2014-08-07T01:01:16Z

In store_mem_state(), we have: ... 334 else if (!strncmp(buf, "offline", min_t(int, count, 7))) 335 online_type = -1; ... 355 case -1: 356 ret = device_offline(&mem->dev); 357 break; ... Here, "offline" is hard coded as -1. This patch does the following renaming: ONLINE_KEEP -> MMOP_ONLINE_KEEP ONLINE_KERNEL -> MMOP_ONLINE_KERNEL ONLINE_MOVABLE -> MMOP_ONLINE_MOVABLE and introduces MMOP_OFFLINE = -1 to avoid hard coding. Signed-off-by: Tang Chen Cc: Hu Tao Cc: Greg Kroah-Hartman Cc: Lai Jiangshan Cc: Yasuaki Ishimatsu Cc: Gu Zheng Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mem-hotplug: avoid illegal state prefixed with legal state when changing state of memory_block

2014-08-07T01:01:16Z

We use the following command to online a memory_block: echo online|online_kernel|online_movable > /sys/devices/system/memory/memoryXXX/state But, if we do the following: echo online_fhsjkghfkd > /sys/devices/system/memory/memoryXXX/state the block will also be onlined. This is because the following code in store_mem_state() does not compare the whole string, but only the prefix of the string. store_mem_state() { ...... 328 if (!strncmp(buf, "online_kernel", min_t(int, count, 13))) Here, only compare the first 13 letters of the string. If we give "online_kernelXXXXXX", it will be recognized as online_kernel, which is incorrect. 329 online_type = ONLINE_KERNEL; 330 else if (!strncmp(buf, "online_movable", min_t(int, count, 14))) We have the same problem here, 331 online_type = ONLINE_MOVABLE; 332 else if (!strncmp(buf, "online", min_t(int, count, 6))) here, (Here is more problematic. If we give online_movalbe, which is a typo of online_movable, it will be recognized as online without noticing the author.) 333 online_type = ONLINE_KEEP; 334 else if (!strncmp(buf, "offline", min_t(int, count, 7))) and here. 335 online_type = -1; 336 else { 337 ret = -EINVAL; 338 goto err; 339 } ...... } This patch fixes this problem by using sysfs_streq() to compare the whole string. Signed-off-by: Tang Chen Reported-by: Hu Tao Cc: Greg Kroah-Hartman Cc: Lai Jiangshan Cc: Yasuaki Ishimatsu Cc: Gu Zheng Acked-by: Toshi Kani Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory-hotplug: update documentation to hide information about SECTIONS and remove end_phys_index

2014-06-04T23:53:58Z

Seems we all agree that information about SECTION, e.g. section size, sections per memory block should be kept as kernel internals, and not exposed to userspace. This patch updates Documentation/memory-hotplug.txt to refer to memory blocks instead of memory sections where appropriate and added a paragraph to explain that memory blocks are made of memory sections. The documentation update is mostly provided by Nathan. Also, as end_phys_index in code is actually not the end section id, but the end memory block id, which should always be the same as phys_index. So it is removed here. Signed-off-by: Li Zhong Reviewed-by: Zhang Yanfei Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds