On Thu, Aug 19, 2010 at 7:34 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> On Thu, Aug 19, 2010 at 01:57:25PM -0700, Michael Rubin wrote:
>> Exporting account_pages_dirty and adding a symmetric routine
>> account_pages_writeback.
>
> s/account_pages_writeback/account_page_writeback/
Got it. thanks.
> I'd recommend to separate the changes into two patches.
> It's actually a bug fix to export account_pages_dirty() for ceph,
> which should be a good candidate for 2.6.36.
Good idea.
>> This allows code outside of the mm core to safely manipulate page state
>> and not worry about the other accounting. Not using these routines means
>> that some code will lose track of the accounting and we get bugs. This
>> has happened once already.
>>
>> Signed-off-by: Michael Rubin <mrubin@xxxxxxxxxx>
>> ---
>> fs/ceph/addr.c | 8 ++------
>> fs/nilfs2/segment.c | 2 +-
>> include/linux/mm.h | 1 +
>> mm/page-writeback.c | 15 +++++++++++++++
>> 4 files changed, 19 insertions(+), 7 deletions(-)
>>
>> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
>> index d9c60b8..359aa3a 100644
>> --- a/fs/ceph/addr.c
>> +++ b/fs/ceph/addr.c
>> @@ -106,12 +106,8 @@ static int ceph_set_page_dirty(struct page *page)
>> if (page->mapping) { /* Race with truncate? */
>> WARN_ON_ONCE(!PageUptodate(page));
>>
>> - if (mapping_cap_account_dirty(mapping)) {
>> - __inc_zone_page_state(page, NR_FILE_DIRTY);
>> - __inc_bdi_stat(mapping->backing_dev_info,
>> - BDI_RECLAIMABLE);
>> - task_io_account_write(PAGE_CACHE_SIZE);
>> - }
>> + if (mapping_cap_account_dirty(mapping))
>
> That 'if' is not necessary. account_page_dirtied() already has one.
> The extra 'if' is not an optimization either, because the ceph fs is
> not likely to have un-accountable mappings.
Sweet. Thanks.
>
>> + account_page_dirtied(page, page->mapping);
>> radix_tree_tag_set(&mapping->page_tree,
>> page_index(page), PAGECACHE_TAG_DIRTY);
>>
>> diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
>> index c920164..967ed7d 100644
>> --- a/fs/nilfs2/segment.c
>> +++ b/fs/nilfs2/segment.c
>> @@ -1599,7 +1599,7 @@ nilfs_copy_replace_page_buffers(struct page *page, struct list_head *out)
>> kunmap_atomic(kaddr, KM_USER0);
>>
>> if (!TestSetPageWriteback(clone_page))
>> - inc_zone_page_state(clone_page, NR_WRITEBACK);
>> + account_page_writeback(clone_page, page_mapping(clone_page));
>> unlock_page(clone_page);
>>
>> return 0;
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index a2b4804..b138392 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -855,6 +855,7 @@ int __set_page_dirty_no_writeback(struct page *page);
>> int redirty_page_for_writepage(struct writeback_control *wbc,
>> struct page *page);
>> void account_page_dirtied(struct page *page, struct address_space *mapping);
>> +void account_page_writeback(struct page *page, struct address_space *mapping);
>> int set_page_dirty(struct page *page);
>> int set_page_dirty_lock(struct page *page);
>> int clear_page_dirty_for_io(struct page *page);
>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
>> index 37498ef..b8e7b3b 100644
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -1096,6 +1096,21 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
>> task_io_account_write(PAGE_CACHE_SIZE);
>> }
>> }
>> +EXPORT_SYMBOL(account_page_dirtied);
>> +
>> +/*
>> + * Helper function for set_page_writeback family.
>> + * NOTE: Unlike account_page_dirtied this does not rely on being atomic
>> + * wrt interrupts.
>> + */
>> +
>> +void account_page_writeback(struct page *page, struct address_space *mapping)
>> +{
>> + if (mapping_cap_account_dirty(mapping))
>
> The 'if' test and *mapping parameter looks unnecessary at least for
> now. The only place a mapping has BDI_CAP_NO_ACCT_WB but not
> BDI_CAP_NO_WRITEBACK is fuse, which does its own accounting.
Cool.
Thanks.
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