lkml.org 
[lkml]   [2009]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] adjust gfp mask passed on nested vmalloc() invocation
    On Mon, 5 Oct 2009, Jan Beulich wrote:

    > - fix a latent bug resulting from blindly or-ing in __GFP_ZERO, since
    > the combination of this and __GFP_HIGHMEM (possibly passed into the
    > function) is forbidden in interrupt context
    > - avoid wasting more precious resources (DMA or DMA32 pools), when
    > being called through vmalloc_32{,_user}()
    > - explicitly allow using high memory here even if the outer allocation
    > request doesn't allow it, unless is collides with __GFP_ZERO
    >
    > Signed-off-by: Jan Beulich <jbeulich@novell.com>

    I thought vmalloc.c was a BUG_ON(in_interrupt()) zone?
    The locking is all spin_lock stuff, not spin_lock_irq stuff.
    That's probably why your "bug" has remained "latent".

    Using HIGHMEM for internal arrays looks reasonable to me; but if
    __GFP_ZERO were a problem, wouldn't it be much cleaner to skip the
    "unless it collides" and #ifdef CONFIG_HIGHMEM !in_interrupt() stuff,
    just memset the array returned from __vmalloc_node()?

    Hugh

    >
    > ---
    > mm/vmalloc.c | 12 ++++++++----
    > 1 file changed, 8 insertions(+), 4 deletions(-)
    >
    > --- linux-2.6.32-rc3/mm/vmalloc.c 2009-10-05 11:59:56.000000000 +0200
    > +++ 2.6.32-rc3-vmalloc-nested-gfp/mm/vmalloc.c 2009-10-05 08:40:36.000000000 +0200
    > @@ -1410,6 +1410,7 @@ static void *__vmalloc_area_node(struct
    > {
    > struct page **pages;
    > unsigned int nr_pages, array_size, i;
    > + gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
    >
    > nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT;
    > array_size = (nr_pages * sizeof(struct page *));
    > @@ -1417,13 +1418,16 @@ static void *__vmalloc_area_node(struct
    > area->nr_pages = nr_pages;
    > /* Please note that the recursion is strictly bounded. */
    > if (array_size > PAGE_SIZE) {
    > - pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
    > +#ifdef CONFIG_HIGHMEM
    > + /* See the comment in prep_zero_page(). */
    > + if (!in_interrupt())
    > + nested_gfp |= __GFP_HIGHMEM;
    > +#endif
    > + pages = __vmalloc_node(array_size, nested_gfp,
    > PAGE_KERNEL, node, caller);
    > area->flags |= VM_VPAGES;
    > } else {
    > - pages = kmalloc_node(array_size,
    > - (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
    > - node);
    > + pages = kmalloc_node(array_size, nested_gfp, node);
    > }
    > area->pages = pages;
    > area->caller = caller;


    \
     
     \ /
      Last update: 2009-10-07 00:05    [W:0.036 / U:0.416 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site