netdev - Re: [PATCH v9 vfio 4/7] vfio/pds: Add VFIO live migration support

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Message-ID: <d245e6aa-8422-0c88-fbe2-42d9af6c1bf4@amd.com>
Date: Fri, 5 May 2023 08:37:23 -0700
From: Brett Creeley <bcreeley@....com>
To: Jason Gunthorpe <jgg@...dia.com>, Brett Creeley <brett.creeley@....com>
Cc: kvm@...r.kernel.org, netdev@...r.kernel.org, alex.williamson@...hat.com,
 yishaih@...dia.com, shameerali.kolothum.thodi@...wei.com,
 kevin.tian@...el.com, shannon.nelson@....com, drivers@...sando.io
Subject: Re: [PATCH v9 vfio 4/7] vfio/pds: Add VFIO live migration support

On 5/4/2023 10:34 AM, Jason Gunthorpe wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> On Fri, Apr 21, 2023 at 06:06:39PM -0700, Brett Creeley wrote:
> 
>> +static struct pds_vfio_lm_file *
>> +pds_vfio_get_lm_file(const struct file_operations *fops, int flags, u64 size)
>> +{
>> +     struct pds_vfio_lm_file *lm_file = NULL;
>> +     unsigned long long npages;
>> +     struct page **pages;
>> +     int err = 0;
>> +
>> +     if (!size)
>> +             return NULL;
>> +
>> +     /* Alloc file structure */
>> +     lm_file = kzalloc(sizeof(*lm_file), GFP_KERNEL);
>> +     if (!lm_file)
>> +             return NULL;
>> +
>> +     /* Create file */
>> +     lm_file->filep = anon_inode_getfile("pds_vfio_lm", fops, lm_file, flags);
>> +     if (!lm_file->filep)
>> +             goto err_get_file;
>> +
>> +     stream_open(lm_file->filep->f_inode, lm_file->filep);
>> +     mutex_init(&lm_file->lock);
>> +
>> +     lm_file->size = size;
>> +
>> +     /* Allocate memory for file pages */
>> +     npages = DIV_ROUND_UP_ULL(lm_file->size, PAGE_SIZE);
>> +
>> +     pages = kcalloc(npages, sizeof(*pages), GFP_KERNEL);
>> +     if (!pages)
>> +             goto err_alloc_pages;
>> +
>> +     for (unsigned long long i = 0; i < npages; i++) {
>> +             pages[i] = alloc_page(GFP_KERNEL);
>> +             if (!pages[i])
>> +                     goto err_alloc_page;
>> +     }
>> +
>> +     lm_file->pages = pages;
>> +     lm_file->npages = npages;
>> +     lm_file->alloc_size = npages * PAGE_SIZE;
>> +
>> +     /* Create scatterlist of file pages to use for DMA mapping later */
>> +     err = sg_alloc_table_from_pages(&lm_file->sg_table, pages, npages,
>> +                                     0, size, GFP_KERNEL);
>> +     if (err)
>> +             goto err_alloc_sg_table;
>> +
>> +     /* prevent file from being released before we are done with it */
>> +     get_file(lm_file->filep);
>> +
>> +     return lm_file;
>> +
>> +err_alloc_sg_table:
>> +err_alloc_page:
> 
> What is with these double error out labels? I see it in a few places,
> that is not the kernel style.
> 
> In VFIO we have been trying to label the err outs based on what they
> free, it is not a 'call from' scheme.
> 
> Jason

Yeah this is kind of ugly. Thanks for pointing it out. I will fix it and 
any other occurrences in the next revision.

Brett