• C
    Make page->private usable in compound pages · d85f3385
    Christoph Lameter 提交于
    If we add a new flag so that we can distinguish between the first page and the
    tail pages then we can avoid to use page->private in the first page.
    page->private == page for the first page, so there is no real information in
    there.
    
    Freeing up page->private makes the use of compound pages more transparent.
    They become more usable like real pages.  Right now we have to be careful f.e.
     if we are going beyond PAGE_SIZE allocations in the slab on i386 because we
    can then no longer use the private field.  This is one of the issues that
    cause us not to support debugging for page size slabs in SLAB.
    
    Having page->private available for SLUB would allow more meta information in
    the page struct.  I can probably avoid the 16 bit ints that I have in there
    right now.
    
    Also if page->private is available then a compound page may be equipped with
    buffer heads.  This may free up the way for filesystems to support larger
    blocks than page size.
    
    We add PageTail as an alias of PageReclaim.  Compound pages cannot currently
    be reclaimed.  Because of the alias one needs to check PageCompound first.
    
    The RFC for the this approach was discussed at
    http://marc.info/?t=117574302800001&r=1&w=2
    
    [nacc@us.ibm.com: fix hugetlbfs]
    Signed-off-by: NChristoph Lameter <clameter@sgi.com>
    Signed-off-by: NNishanth Aravamudan <nacc@us.ibm.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    d85f3385
internal.h 1.0 KB