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    SubjectRe: [RFC PATCH v3 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs
    At 07/09/2012 06:26 PM, Yasuaki Ishimatsu Wrote:
    > When (hot)adding memory into system, /sys/firmware/memmap/X/{end, start, type}
    > sysfs files are created. But there is no code to remove these files. The patch
    > implements the function to remove them.
    >
    > Note : The code does not free firmware_map_entry since there is no way to free
    > memory which is allocated by bootmem.
    >
    > CC: David Rientjes <rientjes@google.com>
    > CC: Jiang Liu <liuj97@gmail.com>
    > CC: Len Brown <len.brown@intel.com>
    > CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    > CC: Paul Mackerras <paulus@samba.org>
    > CC: Christoph Lameter <cl@linux.com>
    > Cc: Minchan Kim <minchan.kim@gmail.com>
    > CC: Andrew Morton <akpm@linux-foundation.org>
    > CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > CC: Wen Congyang <wency@cn.fujitsu.com>
    > Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    >
    > ---
    > drivers/firmware/memmap.c | 78 ++++++++++++++++++++++++++++++++++++++++++-
    > include/linux/firmware-map.h | 6 +++
    > mm/memory_hotplug.c | 6 ++-
    > 3 files changed, 88 insertions(+), 2 deletions(-)
    >
    > Index: linux-3.5-rc6/mm/memory_hotplug.c
    > ===================================================================
    > --- linux-3.5-rc6.orig/mm/memory_hotplug.c 2012-07-09 18:23:13.323844923 +0900
    > +++ linux-3.5-rc6/mm/memory_hotplug.c 2012-07-09 18:23:19.522767424 +0900
    > @@ -661,7 +661,11 @@ EXPORT_SYMBOL_GPL(add_memory);
    >
    > int remove_memory(int nid, u64 start, u64 size)
    > {
    > - return -EBUSY;
    > + lock_memory_hotplug();
    > + /* remove memmap entry */
    > + firmware_map_remove(start, start + size - 1, "System RAM");
    > + unlock_memory_hotplug();
    > + return 0;
    >
    > }
    > EXPORT_SYMBOL_GPL(remove_memory);
    > Index: linux-3.5-rc6/include/linux/firmware-map.h
    > ===================================================================
    > --- linux-3.5-rc6.orig/include/linux/firmware-map.h 2012-07-09 18:23:09.532892314 +0900
    > +++ linux-3.5-rc6/include/linux/firmware-map.h 2012-07-09 18:23:19.523767412 +0900
    > @@ -25,6 +25,7 @@
    >
    > int firmware_map_add_early(u64 start, u64 end, const char *type);
    > int firmware_map_add_hotplug(u64 start, u64 end, const char *type);
    > +int firmware_map_remove(u64 start, u64 end, const char *type);
    >
    > #else /* CONFIG_FIRMWARE_MEMMAP */
    >
    > @@ -38,6 +39,11 @@ static inline int firmware_map_add_hotpl
    > return 0;
    > }
    >
    > +static inline int firmware_map_remove(u64 start, u64 end, const char *type)
    > +{
    > + return 0;
    > +}
    > +
    > #endif /* CONFIG_FIRMWARE_MEMMAP */
    >
    > #endif /* _LINUX_FIRMWARE_MAP_H */
    > Index: linux-3.5-rc6/drivers/firmware/memmap.c
    > ===================================================================
    > --- linux-3.5-rc6.orig/drivers/firmware/memmap.c 2012-07-09 18:23:09.532892314 +0900
    > +++ linux-3.5-rc6/drivers/firmware/memmap.c 2012-07-09 18:25:46.371931554 +0900
    > @@ -21,6 +21,7 @@
    > #include <linux/types.h>
    > #include <linux/bootmem.h>
    > #include <linux/slab.h>
    > +#include <linux/mm.h>
    >
    > /*
    > * Data types ------------------------------------------------------------------
    > @@ -79,7 +80,22 @@ static const struct sysfs_ops memmap_att
    > .show = memmap_attr_show,
    > };
    >
    > +#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
    > +
    > +static void release_firmware_map_entry(struct kobject *kobj)
    > +{
    > + struct firmware_map_entry *entry = to_memmap_entry(kobj);
    > + struct page *head_page;
    > +
    > + head_page = virt_to_head_page(entry);
    > + if (PageSlab(head_page))
    > + kfree(entry);
    > +
    > + /* There is no way to free memory allocated from bootmem*/
    > +}
    > +
    > static struct kobj_type memmap_ktype = {
    > + .release = release_firmware_map_entry,
    > .sysfs_ops = &memmap_attr_ops,
    > .default_attrs = def_attrs,
    > };
    > @@ -123,6 +139,16 @@ static int firmware_map_add_entry(u64 st
    > return 0;
    > }
    >
    > +/**
    > + * firmware_map_remove_entry() - Does the real work to remove a firmware
    > + * memmap entry.
    > + * @entry: removed entry.
    > + **/
    > +static inline void firmware_map_remove_entry(struct firmware_map_entry *entry)
    > +{
    > + list_del(&entry->list);
    > +}
    > +
    > /*
    > * Add memmap entry on sysfs
    > */
    > @@ -144,6 +170,31 @@ static int add_sysfs_fw_map_entry(struct
    > return 0;
    > }
    >
    > +/*
    > + * Remove memmap entry on sysfs
    > + */
    > +static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
    > +{
    > + kobject_put(&entry->kobj);
    > +}
    > +
    > +/*
    > + * Search memmap entry
    > + */
    > +
    > +struct firmware_map_entry * __meminit
    > +find_firmware_map_entry(u64 start, u64 end, const char *type)
    > +{
    > + struct firmware_map_entry *entry;
    > +
    > + list_for_each_entry(entry, &map_entries, list)
    > + if ((entry->start == start) && (entry->end == end) &&
    > + (!strcmp(entry->type, type)))
    > + return entry;
    > +
    > + return NULL;
    > +}
    > +
    > /**
    > * firmware_map_add_hotplug() - Adds a firmware mapping entry when we do
    > * memory hotplug.
    > @@ -196,6 +247,32 @@ int __init firmware_map_add_early(u64 st
    > return firmware_map_add_entry(start, end, type, entry);
    > }
    >
    > +/**
    > + * firmware_map_remove() - remove a firmware mapping entry
    > + * @start: Start of the memory range.
    > + * @end: End of the memory range (inclusive).
    > + * @type: Type of the memory range.
    > + *
    > + * removes a firmware mapping entry.
    > + *
    > + * Returns 0 on success, or -EINVAL if no entry.
    > + **/
    > +int __meminit firmware_map_remove(u64 start, u64 end, const char *type)
    > +{
    > + struct firmware_map_entry *entry;
    > +
    > + entry = find_firmware_map_entry(start, end, type);
    > + if (!entry)
    > + return -EINVAL;
    > +
    > + /* remove the memmap entry */
    > + remove_sysfs_fw_map_entry(entry);
    > +
    > + firmware_map_remove_entry(entry);

    You should call firmware_map_remove_entry() before remove_sysfs_fw_map_entry(),
    otherwise it will cause kernel panicked(entry may be freed in remove_sysfs_fw_map_entry()).

    Thanks
    Wen Congyang

    > +
    > + return 0;
    > +}
    > +
    > /*
    > * Sysfs functions -------------------------------------------------------------
    > */
    > @@ -218,7 +295,6 @@ static ssize_t type_show(struct firmware
    > }
    >
    > #define to_memmap_attr(_attr) container_of(_attr, struct memmap_attribute, attr)
    > -#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
    >
    > static ssize_t memmap_attr_show(struct kobject *kobj,
    > struct attribute *attr, char *buf)
    >
    >



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