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SubjectRE: [PATCH 4/9] staging: fsl-mc: don't use devres api for refcounted objects
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> -----Original Message-----
> From: laurentiu.tudor@nxp.com [mailto:laurentiu.tudor@nxp.com]
> Sent: Wednesday, February 01, 2017 5:43 AM
> To: gregkh@linuxfoundation.org
> Cc: devel@driverdev.osuosl.org; linux-kernel@vger.kernel.org; agraf@suse.de; arnd@arndb.de; Ioana
> Ciornei <ioana.ciornei@nxp.com>; Ruxandra Ioana Radulescu <ruxandra.radulescu@nxp.com>; Bharat Bhushan
> <bharat.bhushan@nxp.com>; Stuart Yoder <stuart.yoder@nxp.com>; Catalin Horghidan
> <catalin.horghidan@nxp.com>; Leo Li <leoyang.li@nxp.com>; Roy Pledge <roy.pledge@nxp.com>; Laurentiu
> Tudor <laurentiu.tudor@nxp.com>
> Subject: [PATCH 4/9] staging: fsl-mc: don't use devres api for refcounted objects
>
> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>
> Mixing two memory management systems, in this case
> managed device resource api and refcounted objects
> is a bad idea. Lifetime of an object is controlled
> by its refcount so allocating it with other apis
> that have their own lifetime control is not ok.
> Drop devm_*() apis in favor of plain allocations.
>
> While at it, let's drop the slab cache for objects
> until we actually have proof that it improves
> performance. This allows for some code cleanup.

Those 2 changes (dropping devm_* apis and slab cache
changes) are 2 orthogonal things, right? It would
be better to split those into separate patches. Mixing
them makes it harder to review.

> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
> ---
> drivers/staging/fsl-mc/bus/fsl-mc-bus.c | 43 +++++----------------------------
> 1 file changed, 6 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/staging/fsl-mc/bus/fsl-mc-bus.c b/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> index 6601bde..c493427 100644
> --- a/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> +++ b/drivers/staging/fsl-mc/bus/fsl-mc-bus.c
> @@ -27,8 +27,6 @@
> #include "fsl-mc-private.h"
> #include "dprc-cmd.h"
>
> -static struct kmem_cache *mc_dev_cache;
> -
> /**
> * Default DMA mask for devices on a fsl-mc bus
> */
> @@ -422,17 +420,12 @@ bool fsl_mc_is_root_dprc(struct device *dev)
> static void fsl_mc_device_release(struct device *dev)
> {
> struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
> - struct fsl_mc_bus *mc_bus = NULL;
>
> kfree(mc_dev->regions);
> -
> - if (strcmp(mc_dev->obj_desc.type, "dprc") == 0)
> - mc_bus = to_fsl_mc_bus(mc_dev);
> -
> - if (mc_bus)
> - devm_kfree(mc_dev->dev.parent, mc_bus);
> + if (!strcmp(mc_dev->obj_desc.type, "dprc"))
> + kfree(to_fsl_mc_bus(mc_dev));
> else
> - kmem_cache_free(mc_dev_cache, mc_dev);
> + kfree(mc_dev);
> }
>
> /**
> @@ -457,7 +450,7 @@ int fsl_mc_device_add(struct dprc_obj_desc *obj_desc,
> /*
> * Allocate an MC bus device object:
> */
> - mc_bus = devm_kzalloc(parent_dev, sizeof(*mc_bus), GFP_KERNEL);
> + mc_bus = kzalloc(sizeof(*mc_bus), GFP_KERNEL);
> if (!mc_bus)
> return -ENOMEM;
>
> @@ -466,7 +459,7 @@ int fsl_mc_device_add(struct dprc_obj_desc *obj_desc,
> /*
> * Allocate a regular fsl_mc_device object:
> */
> - mc_dev = kmem_cache_zalloc(mc_dev_cache, GFP_KERNEL);
> + mc_dev = kzalloc(sizeof(*mc_dev), GFP_KERNEL);
> if (!mc_dev)
> return -ENOMEM;
> }
> @@ -561,10 +554,7 @@ int fsl_mc_device_add(struct dprc_obj_desc *obj_desc,
>
> error_cleanup_dev:
> kfree(mc_dev->regions);
> - if (mc_bus)
> - devm_kfree(parent_dev, mc_bus);
> - else
> - kmem_cache_free(mc_dev_cache, mc_dev);
> + kfree(mc_bus ? (void *)mc_bus : (void *)mc_dev);
>
> return error;
> }
> @@ -578,23 +568,11 @@ int fsl_mc_device_add(struct dprc_obj_desc *obj_desc,
> */
> void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
> {
> - struct fsl_mc_bus *mc_bus = NULL;
> -
> - kfree(mc_dev->regions);
> -
> /*
> * The device-specific remove callback will get invoked by device_del()
> */
> device_del(&mc_dev->dev);
> put_device(&mc_dev->dev);
> -
> - if (strcmp(mc_dev->obj_desc.type, "dprc") == 0)
> - mc_bus = to_fsl_mc_bus(mc_dev);
> -
> - if (mc_bus)
> - devm_kfree(mc_dev->dev.parent, mc_bus);
> - else
> - kmem_cache_free(mc_dev_cache, mc_dev);
> }

The above changes in fsl_mc_device_remove(), I think
actually belong in patch #3 of this series.

Stuart

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