• Konstantin Khlebnikov's avatar
    page_writeback: clean up mess around cancel_dirty_page() · b9ea2515
    Konstantin Khlebnikov authored
    This patch replaces cancel_dirty_page() with a helper function
    account_page_cleaned() which only updates counters.  It's called from
    truncate_complete_page() and from try_to_free_buffers() (hack for ext3).
    Page is locked in both cases, page-lock protects against concurrent
    dirtiers: see commit 2d6d7f98 ("mm: protect set_page_dirty() from
    ongoing truncation").
    Delete_from_page_cache() shouldn't be called for dirty pages, they must
    be handled by caller (either written or truncated).  This patch treats
    final dirty accounting fixup at the end of __delete_from_page_cache() as
    a debug check and adds WARN_ON_ONCE() around it.  If something removes
    dirty pages without proper handling that might be a bug and unwritten
    data might be lost.
    Hugetlbfs has no dirty pages accounting, ClearPageDirty() is enough
    cancel_dirty_page() in nfs_wb_page_cancel() is redundant.  This is
    helper for nfs_invalidate_page() and it's called only in case complete
    The mess was started in v2.6.20 after commits 46d2277c ("Clean up
    and make try_to_free_buffers() not race with dirty pages") and
    3e67c098 ("truncate: clear page dirtiness before running
    try_to_free_buffers()") first was reverted right in v2.6.20 in commit
    ecdfc978 ("Resurrect 'try_to_free_buffers()' VM hackery"), second in
    v2.6.25 commit a2b34564 ("Fix dirty page accounting leak with ext3
    Custom fixes were introduced between these points.  NFS in v2.6.23, commit
    1b3b4a1a ("NFS: Fix a write request leak in nfs_invalidate_page()").
    Kludge in __delete_from_page_cache() in v2.6.24, commit 3a692790 ("Do
    dirty page accounting when removing a page from the page cache").  Since
    v2.6.25 all of them are redundant.
    [akpm@linux-foundation.org: coding-style fixes]
    Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Jan Kara <jack@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
buffer.c 88.8 KB