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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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