Re: [RFC PATCH] memory-hotplug: Add memblock_state notifier
From: Wen Congyang <hidden>
Date: 2012-07-23 09:04:05
Also in:
linux-mm, lkml
At 07/20/2012 07:18 PM, Vasilis Liaskovitis Wrote:
hot-remove initiated by acpi_memhotplug driver tries to offline pages and then remove section/sysfs files in remove_memory(). remove_memory() will only proceed if is_memblk_offline() returns true, i.e. only if the corresponding memblock is in MEM_OFFLINE state. However, the memblock state is currently only updated if the offlining has been initiated from the sysfs interface (echo offline > /sys/devices/system/memory/memoryXX/state). The acpi hot-remove codepath does not use the sysfs interface but directly calls offline_pages. So remove_memory() will always fail, even if offline_pages has succeeded.
Thank you for pointing this problem.
This patch solves this by registering a memblock_state notifier function in the memory_notify chain. This will change state of memblocks independently of sysfs usage.
I think this patch does not solve this problem.
quoted hunk ↗ jump to hunk
The patch is based on work-in-progress patches for memory hot-remove, see: http://lwn.net/Articles/507244/ Signed-off-by: Vasilis Liaskovitis <redacted> --- drivers/base/memory.c | 37 +++++++++++++++++++++++++++++++++++++ 1 files changed, 37 insertions(+), 0 deletions(-)diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 8981568..4095f3f 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c@@ -706,6 +706,42 @@ int unregister_memory_section(struct mem_section *section) return remove_memory_block(0, section, 0); } +static int memblock_state_notifier_nb(struct notifier_block *nb, unsigned long + val, void *v) +{ + struct memory_notify *arg = (struct memory_notify *)v; + struct memory_block *mem = NULL; + struct mem_section *ms; + unsigned long section_nr; + + section_nr = pfn_to_section_nr(arg->start_pfn); + ms = __nr_to_section(section_nr); + mem = find_memory_block(ms); + if (!mem) + goto out;
we may offline more than one memory block.
+
+ switch (val) {
+ case MEM_GOING_OFFLINE:
+ case MEM_OFFLINE:
+ case MEM_GOING_ONLINE:
+ case MEM_ONLINE:
+ case MEM_CANCEL_ONLINE:
+ case MEM_CANCEL_OFFLINE:
+ mem->state = val;
mem->state is protected by the lock mem->state_mutex, so if you want to
update the state, you must lock mem->state_mutex. But you cannot lock it
here, because it may cause deadlock:
acpi_memhotplug sysfs interface
===============================================================================
memory_block_change_state()
lock mem->state_mutex
memory_block_action()
offline_pages()
lock_memory_hotplug()
offline_memory()
lock_memory_hotplug() // block
memory_notify()
memblock_state_notifier_nb()
===============================================================================
I'm writing another patch to fix it.
Thanks
Wen Congyang
quoted hunk ↗ jump to hunk
+ break; + default: + printk(KERN_WARNING "invalid memblock state\n"); + break; + } +out: + return NOTIFY_OK; +} + +static struct notifier_block memblock_state_nb = { + .notifier_call = memblock_state_notifier_nb, + .priority = 0 +}; + /* * Initialize the sysfs support for memory devices... */@@ -724,6 +760,7 @@ int __init memory_dev_init(void) block_sz = get_memory_block_size(); sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE; + register_memory_notifier(&memblock_state_nb); /* * Create entries for memory sections that were found * during boot and have been initialized
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