linux-kernel - Re: [PATCH v2] cxl/memdev: automate cleanup with _

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Message-ID: <CAH4c4jLAfMTn6wN3wJSOQZ3mAoYC3uhswDu6c+c6v-wv8mSifQ@mail.gmail.com>
Date: Thu, 26 Jun 2025 20:02:10 +0530
From: Pranav Tyagi <pranav.tyagi03@...il.com>
To: Robert Richter <rrichter@....com>
Cc: dave@...olabs.net, jonathan.cameron@...wei.com, dave.jiang@...el.com, 
	alison.schofield@...el.com, vishal.l.verma@...el.com, ira.weiny@...el.com, 
	dan.j.williams@...el.com, linux-cxl@...r.kernel.org, 
	linux-kernel@...r.kernel.org, ming.li@...omail.com, peterz@...radead.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH v2] cxl/memdev: automate cleanup with __free()

On Tue, Jun 24, 2025 at 8:47 PM Robert Richter <rrichter@....com> wrote:
>
> On 23.06.25 14:08:41, Pranav Tyagi wrote:
> > Use the scope based resource management (defined in linux/cleanup.h) to
> > automate the lifetime control of struct cxl_mbox_transfer_fw. This
> > eliminates explicit kfree() calls and makes the code more robust and
> > maintainable in presence of early returns.
> >
> > Signed-off-by: Pranav Tyagi <pranav.tyagi03@...il.com>
> > ---
> >  drivers/cxl/core/memdev.c | 21 ++++++++-------------
> >  1 file changed, 8 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> > index f88a13adf7fa..38f4449f9740 100644
> > --- a/drivers/cxl/core/memdev.c
> > +++ b/drivers/cxl/core/memdev.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/idr.h>
> >  #include <linux/pci.h>
> > +#include <linux/cleanup.h>
> >  #include <cxlmem.h>
> >  #include "trace.h"
> >  #include "core.h"
> > @@ -802,11 +803,10 @@ static int cxl_mem_activate_fw(struct cxl_memdev_state *mds, int slot)
> >  static int cxl_mem_abort_fw_xfer(struct cxl_memdev_state *mds)
> >  {
> >       struct cxl_mailbox *cxl_mbox = &mds->cxlds.cxl_mbox;
> > -     struct cxl_mbox_transfer_fw *transfer;
> >       struct cxl_mbox_cmd mbox_cmd;
> > -     int rc;
> > -
> > -     transfer = kzalloc(struct_size(transfer, data, 0), GFP_KERNEL);
> > +
> > +     struct cxl_mbox_transfer_fw *transfer __free(kfree) =
> > +             kzalloc(struct_size(transfer, data, 0), GFP_KERNEL);
>
> I don't see a reason for __free() here as there are no early exits.
>
> >       if (!transfer)
> >               return -ENOMEM;
> >
> > @@ -821,9 +821,7 @@ static int cxl_mem_abort_fw_xfer(struct cxl_memdev_state *mds)
> >
> >       transfer->action = CXL_FW_TRANSFER_ACTION_ABORT;
> >
> > -     rc = cxl_internal_send_cmd(cxl_mbox, &mbox_cmd);
> > -     kfree(transfer);
> > -     return rc;
> > +     return cxl_internal_send_cmd(cxl_mbox, &mbox_cmd);
> >  }
> >
> >  static void cxl_fw_cleanup(struct fw_upload *fwl)
> > @@ -880,7 +878,7 @@ static enum fw_upload_err cxl_fw_write(struct fw_upload *fwl, const u8 *data,
> >       struct cxl_dev_state *cxlds = &mds->cxlds;
> >       struct cxl_mailbox *cxl_mbox = &cxlds->cxl_mbox;
> >       struct cxl_memdev *cxlmd = cxlds->cxlmd;
> > -     struct cxl_mbox_transfer_fw *transfer;
> > +     struct cxl_mbox_transfer_fw *transfer __free(kfree);
>
> Jonathan already catched this.
>
> >       struct cxl_mbox_cmd mbox_cmd;
> >       u32 cur_size, remaining;
> >       size_t size_in;
> > @@ -949,7 +947,7 @@ static enum fw_upload_err cxl_fw_write(struct fw_upload *fwl, const u8 *data,
> >       rc = cxl_internal_send_cmd(cxl_mbox, &mbox_cmd);
> >       if (rc < 0) {
> >               rc = FW_UPLOAD_ERR_RW_ERROR;
> > -             goto out_free;
> > +             return rc;
>
> If you want to remove the goto here, just free transfer right after
> calling cxl_internal_send_cmd(). It is no longer used then.
>
> I only want those cleanup helpers where they are actually useful and
> do not just add complexity.
>
> Thanks,
>
> -Robert
>
> >       }
> >
> >       *written = cur_size;
> > @@ -963,14 +961,11 @@ static enum fw_upload_err cxl_fw_write(struct fw_upload *fwl, const u8 *data,
> >                       dev_err(&cxlmd->dev, "Error activating firmware: %d\n",
> >                               rc);
> >                       rc = FW_UPLOAD_ERR_HW_ERROR;
> > -                     goto out_free;
> > +                     return rc;
> >               }
> >       }
> >
> >       rc = FW_UPLOAD_ERR_NONE;
> > -
> > -out_free:
> > -     kfree(transfer);
> >       return rc;
> >  }
> >
> > --
> > 2.49.0
> >

Thank you for the feedback. I understand your concerns and completely
agree with your reasoning. Please pardon my misjudgment in sending this
patch. I am still a beginner with kernel development and learning to
better assess what makes a meaningful contribution.

Regards
Pranav Tyagi