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    SubjectRe: [PATCH v1 06/10] powerpc/pseries/iommu: Add ddw_list_add() helper
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    On 18/08/2020 09:40, Leonardo Bras wrote:
    > There are two functions adding DDW to the direct_window_list in a
    > similar way, so create a ddw_list_add() to avoid duplicity and
    > simplify those functions.
    >
    > Also, on enable_ddw(), add list_del() on out_free_window to allow
    > removing the window from list if any error occurs.
    >
    > Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
    > ---
    > arch/powerpc/platforms/pseries/iommu.c | 42 ++++++++++++++++----------
    > 1 file changed, 26 insertions(+), 16 deletions(-)
    >
    > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
    > index 39617ce0ec83..fcdefcc0f365 100644
    > --- a/arch/powerpc/platforms/pseries/iommu.c
    > +++ b/arch/powerpc/platforms/pseries/iommu.c
    > @@ -872,6 +872,24 @@ static u64 find_existing_ddw(struct device_node *pdn)
    > return dma_addr;
    > }
    >
    > +static struct direct_window *ddw_list_add(struct device_node *pdn,
    > + const struct dynamic_dma_window_prop *dma64)
    > +{
    > + struct direct_window *window;
    > +
    > + window = kzalloc(sizeof(*window), GFP_KERNEL);
    > + if (!window)
    > + return NULL;
    > +
    > + window->device = pdn;
    > + window->prop = dma64;
    > + spin_lock(&direct_window_list_lock);
    > + list_add(&window->list, &direct_window_list);
    > + spin_unlock(&direct_window_list_lock);
    > +
    > + return window;
    > +}
    > +
    > static int find_existing_ddw_windows(void)
    > {
    > int len;
    > @@ -887,18 +905,11 @@ static int find_existing_ddw_windows(void)
    > if (!direct64)
    > continue;
    >
    > - window = kzalloc(sizeof(*window), GFP_KERNEL);
    > - if (!window || len < sizeof(struct dynamic_dma_window_prop)) {
    > + window = ddw_list_add(pdn, direct64);
    > + if (!window || len < sizeof(*direct64)) {


    Since you are touching this code, it looks like the "len <
    sizeof(*direct64)" part should go above to "if (!direct64)".



    > kfree(window);
    > remove_ddw(pdn, true);
    > - continue;
    > }
    > -
    > - window->device = pdn;
    > - window->prop = direct64;
    > - spin_lock(&direct_window_list_lock);
    > - list_add(&window->list, &direct_window_list);
    > - spin_unlock(&direct_window_list_lock);
    > }
    >
    > return 0;
    > @@ -1261,7 +1272,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
    > dev_dbg(&dev->dev, "created tce table LIOBN 0x%x for %pOF\n",
    > create.liobn, dn);
    >
    > - window = kzalloc(sizeof(*window), GFP_KERNEL);
    > + /* Add new window to existing DDW list */

    The comment seems to duplicate what the ddw_list_add name already suggests.


    > + window = ddw_list_add(pdn, ddwprop);
    > if (!window)
    > goto out_clear_window;
    >
    > @@ -1280,16 +1292,14 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
    > goto out_free_window;
    > }
    >
    > - window->device = pdn;
    > - window->prop = ddwprop;
    > - spin_lock(&direct_window_list_lock);
    > - list_add(&window->list, &direct_window_list);
    > - spin_unlock(&direct_window_list_lock);

    I'd leave these 3 lines here and in find_existing_ddw_windows() (which
    would make ddw_list_add -> ddw_prop_alloc). In general you want to have
    less stuff to do on the failure path. kmalloc may fail and needs kfree
    but you can safely delay list_add (which cannot fail) and avoid having
    the lock help twice in the same function (one of them is hidden inside
    ddw_list_add).

    Not sure if this change is really needed after all. Thanks,

    > -
    > dma_addr = be64_to_cpu(ddwprop->dma_base);
    > goto out_unlock;
    >
    > out_free_window:
    > + spin_lock(&direct_window_list_lock);
    > + list_del(&window->list);
    > + spin_unlock(&direct_window_list_lock);
    > +
    > kfree(window);
    >
    > out_clear_window:
    >

    --
    Alexey

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