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SubjectRe: NR_UNSTABLE_FS vs. NR_FILE_DIRTY: double counting pages?
Trond Myklebust wrote:
> On Fri, 2007-04-27 at 18:21 -0700, Ethan Solomita wrote:
>> There are several places where we add together NR_UNSTABLE_FS and
>> NF_FILE_DIRTY:
>>
>> sync_inodes_sb()
>> balance_dirty_pages()
>> wakeup_pdflush()
>> wb_kupdate()
>> prefetch_suitable()
>>
>> I can trace a standard codepath where it seems both of these are set
>> on the same page:
>>
>> nfs_file_aops.commit_write ->
>> nfs_commit_write
>> nfs_updatepages
>> nfs_writepage_setup
>> nfs_wb_page
>> nfs_wb_page_priority
>> nfs_writepage_locked
>> nfs_flush_mapping
>> nfs_flush_list
>> nfs_flush_multi
>> nfs_write_partial_ops.rpc_call_done
>> nfs_writeback_done_partial
>> nfs_writepage_release
>> nfs_reschedule_unstable_write
>> nfs_mark_request_commit
>> incr NR_UNSTABLE_NFS
>>
>> nfs_file_aops.commit_write ->
>> nfs_commit_write
>> nfs_updatepage
>> __set_page_dirty_nobuffers
>> incr NF_FILE_DIRTY
>>
>>
>> This is the standard code path that derives from sys_write(). Can
>> someone either show how this code sequence can't happen, or confirm for
>> me that there's a bug?
>> -- Ethan
>
> It should not happen. If the page is on the unstable list, then it will
> be committed before nfs_updatepage is allowed to redirty it. See the
> recent fixes in 2.6.21-rc7.

Above I present a codepath called straight from sys_write() which seems
to do what I say. I could be wrong, but can you address the code paths I
show above which seem to set both?
-- Ethan
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