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SubjectRe: [RFC PATCH 1/4] mm: introduce a safer interface to check whether a page is managed by SLxB
Need to simplify the patch set:)
Busy with PCI patches recently and will work on this when PCI is done.

On 2012-9-4 17:18, Wen Congyang wrote:
> At 07/03/2012 11:57 AM, Jiang Liu Wrote:
>> Several subsystems, including memory-failure, swap, sparse, DRBD etc,
>> use PageSlab() to check whether a page is managed by SLAB/SLUB/SLOB.
>> And they treat slab pages differently from pagecache/anonymous pages.
>>
>> But it's unsafe to use PageSlab() to detect whether a page is managed by
>> SLUB. SLUB allocates compound pages when page order is bigger than 0 and
>> only sets PG_slab on head pages. So if a SLUB object is hosted by a tail
>> page, PageSlab() will incorrectly return false for that object.
>>
>> Following code from sparse.c triggers this issue, which causes failure
>> when removing a hot-added memory device.
>
> Hi, Liu
>
> What is the status of this patch?
> I encounter the same problem when removing a hot-added memory device. It
> causes the kernel panicked
>
> Thanks
> Wen Congyang
>
>> /*
>> * Check to see if allocation came from hot-plug-add
>> */
>> if (PageSlab(usemap_page)) {
>> kfree(usemap);
>> if (memmap)
>> __kfree_section_memmap(memmap, PAGES_PER_SECTION);
>> return;
>> }
>>
>> So introduce a transparent huge page and compound page safe macro as below
>> to check whether a page is managed by SLAB/SLUB/SLOB allocator.
>>
>> #define page_managed_by_slab(page) (!!PageSlab(compound_trans_head(page)))
>>
>> Signed-off-by: Jiang Liu <liuj97@gmail.com>
>> ---
>> arch/arm/mm/init.c | 3 ++-
>> arch/ia64/kernel/mca_drv.c | 2 +-
>> arch/unicore32/mm/init.c | 3 ++-
>> crypto/scatterwalk.c | 2 +-
>> drivers/ata/libata-sff.c | 3 ++-
>> drivers/block/drbd/drbd_main.c | 3 ++-
>> fs/proc/page.c | 4 ++--
>> include/linux/slab.h | 7 +++++++
>> mm/memory-failure.c | 6 +++---
>> mm/sparse.c | 4 +---
>> 10 files changed, 23 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
>> index f54d592..73ff340 100644
>> --- a/arch/arm/mm/init.c
>> +++ b/arch/arm/mm/init.c
>> @@ -18,6 +18,7 @@
>> #include <linux/initrd.h>
>> #include <linux/of_fdt.h>
>> #include <linux/highmem.h>
>> +#include <linux/huge_mm.h>
>> #include <linux/gfp.h>
>> #include <linux/memblock.h>
>> #include <linux/dma-contiguous.h>
>> @@ -116,7 +117,7 @@ void show_mem(unsigned int filter)
>> reserved++;
>> else if (PageSwapCache(page))
>> cached++;
>> - else if (PageSlab(page))
>> + else if (page_managed_by_slab(page))
>> slab++;
>> else if (!page_count(page))
>> free++;
>> diff --git a/arch/ia64/kernel/mca_drv.c b/arch/ia64/kernel/mca_drv.c
>> index 1c2e894..4415bb6 100644
>> --- a/arch/ia64/kernel/mca_drv.c
>> +++ b/arch/ia64/kernel/mca_drv.c
>> @@ -136,7 +136,7 @@ mca_page_isolate(unsigned long paddr)
>> return ISOLATE_NG;
>>
>> /* kick pages having attribute 'SLAB' or 'Reserved' */
>> - if (PageSlab(p) || PageReserved(p))
>> + if (page_managed_by_slab(p) || PageReserved(p))
>> return ISOLATE_NG;
>>
>> /* add attribute 'Reserved' and register the page */
>> diff --git a/arch/unicore32/mm/init.c b/arch/unicore32/mm/init.c
>> index de186bd..829a0d9 100644
>> --- a/arch/unicore32/mm/init.c
>> +++ b/arch/unicore32/mm/init.c
>> @@ -21,6 +21,7 @@
>> #include <linux/sort.h>
>> #include <linux/dma-mapping.h>
>> #include <linux/export.h>
>> +#include <linux/huge_mm.h>
>>
>> #include <asm/sections.h>
>> #include <asm/setup.h>
>> @@ -83,7 +84,7 @@ void show_mem(unsigned int filter)
>> reserved++;
>> else if (PageSwapCache(page))
>> cached++;
>> - else if (PageSlab(page))
>> + else if (page_managed_by_slab(page))
>> slab++;
>> else if (!page_count(page))
>> free++;
>> diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
>> index 7281b8a..a20e019 100644
>> --- a/crypto/scatterwalk.c
>> +++ b/crypto/scatterwalk.c
>> @@ -54,7 +54,7 @@ static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
>> struct page *page;
>>
>> page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
>> - if (!PageSlab(page))
>> + if (!page_managed_by_slab(page))
>> flush_dcache_page(page);
>> }
>>
>> diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
>> index d8af325..1ab8378 100644
>> --- a/drivers/ata/libata-sff.c
>> +++ b/drivers/ata/libata-sff.c
>> @@ -38,6 +38,7 @@
>> #include <linux/module.h>
>> #include <linux/libata.h>
>> #include <linux/highmem.h>
>> +#include <linux/huge_mm.h>
>>
>> #include "libata.h"
>>
>> @@ -734,7 +735,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
>> do_write);
>> }
>>
>> - if (!do_write && !PageSlab(page))
>> + if (!do_write && !page_managed_by_slab(page))
>> flush_dcache_page(page);
>>
>> qc->curbytes += qc->sect_size;
>> diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
>> index 920ede2..de5b395 100644
>> --- a/drivers/block/drbd/drbd_main.c
>> +++ b/drivers/block/drbd/drbd_main.c
>> @@ -2734,7 +2734,8 @@ static int _drbd_send_page(struct drbd_conf *mdev, struct page *page,
>> * put_page(); and would cause either a VM_BUG directly, or
>> * __page_cache_release a page that would actually still be referenced
>> * by someone, leading to some obscure delayed Oops somewhere else. */
>> - if (disable_sendpage || (page_count(page) < 1) || PageSlab(page))
>> + if (disable_sendpage || (page_count(page) < 1) ||
>> + page_managed_by_slab(page))
>> return _drbd_no_send_page(mdev, page, offset, size, msg_flags);
>>
>> msg_flags |= MSG_NOSIGNAL;
>> diff --git a/fs/proc/page.c b/fs/proc/page.c
>> index 7fcd0d6..ae42dc7 100644
>> --- a/fs/proc/page.c
>> +++ b/fs/proc/page.c
>> @@ -40,7 +40,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
>> ppage = pfn_to_page(pfn);
>> else
>> ppage = NULL;
>> - if (!ppage || PageSlab(ppage))
>> + if (!ppage || page_managed_by_slab(ppage))
>> pcount = 0;
>> else
>> pcount = page_mapcount(ppage);
>> @@ -98,7 +98,7 @@ u64 stable_page_flags(struct page *page)
>> * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
>> * simple test in page_mapped() is not enough.
>> */
>> - if (!PageSlab(page) && page_mapped(page))
>> + if (!page_managed_by_slab(page) && page_mapped(page))
>> u |= 1 << KPF_MMAP;
>> if (PageAnon(page))
>> u |= 1 << KPF_ANON;
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 67d5d94..bb26fab 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -364,4 +364,11 @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
>>
>> void __init kmem_cache_init_late(void);
>>
>> +/*
>> + * Check whether a page is allocated/managed by SLAB/SLUB/SLOB allocator.
>> + * Defined as macro instead of function to avoid header file pollution.
>> + */
>> +#define page_managed_by_slab(page) (!!PageSlab(compound_trans_head(page)))
>> +#define mem_managed_by_slab(addr) page_managed_by_slab(virt_to_page(addr))
>> +
>> #endif /* _LINUX_SLAB_H */
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index ab1e714..684e7f7 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -88,7 +88,7 @@ static int hwpoison_filter_dev(struct page *p)
>> /*
>> * page_mapping() does not accept slab pages.
>> */
>> - if (PageSlab(p))
>> + if (page_managed_by_slab(p))
>> return -EINVAL;
>>
>> mapping = page_mapping(p);
>> @@ -233,7 +233,7 @@ static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
>> */
>> void shake_page(struct page *p, int access)
>> {
>> - if (!PageSlab(p)) {
>> + if (!page_managed_by_slab(p)) {
>> lru_add_drain_all();
>> if (PageLRU(p))
>> return;
>> @@ -862,7 +862,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
>> struct page *hpage = compound_head(p);
>> struct page *ppage;
>>
>> - if (PageReserved(p) || PageSlab(p))
>> + if (PageReserved(p) || page_managed_by_slab(p))
>> return SWAP_SUCCESS;
>>
>> /*
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 6a4bf91..32a908b 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -688,17 +688,15 @@ static void free_map_bootmem(struct page *page, unsigned long nr_pages)
>>
>> static void free_section_usemap(struct page *memmap, unsigned long *usemap)
>> {
>> - struct page *usemap_page;
>> unsigned long nr_pages;
>>
>> if (!usemap)
>> return;
>>
>> - usemap_page = virt_to_page(usemap);
>> /*
>> * Check to see if allocation came from hot-plug-add
>> */
>> - if (PageSlab(usemap_page)) {
>> + if (mem_managed_by_slab(usemap)) {
>> kfree(usemap);
>> if (memmap)
>> __kfree_section_memmap(memmap, PAGES_PER_SECTION);
>
>
> .
>




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