Re: [PATCH RFT 0/3] mm, drm: ensure .fault() does not have to be followed by .pfn_mkwrite() for write faults

[Paolo Bonzini]

On 8/3/26 10:55, David Hildenbrand (Arm) wrote:
On 7/31/26 18:05, Paolo Bonzini wrote:
Reported-by: Sergio Lopez <s...@redhat.com>

Reported-by: without Fixes: is odd.

Fixes: 6da8e9634bb7 ("mm: new follow_pfnmap API") would also be odd :) 
but I can certainly add it.
+        * @write_fault: if true, fail with -EFAULT unless the mapping is

Just wondering whether EPERM would be better.

It would be EACCES if anything, not EPERM; but almost all callers 
already pass EFAULT to userspace, and write() to a PROT_READ area 
returns EFAULT, so I don't think EACCES is the right choice.

+        * writable
         */
        struct vm_area_struct *vma;
        unsigned long address;
+       bool write_fault;

"write_fault" is a rather odd name for this, given that this function will not
trigger a write fault.

You want something that matches FOLL_WRITE.

"write_access" / "check_writable" maybe?
There are no for_write, write_access or check_write in mm/,  but there 
are a handful of each of these

        int write = (gup_flags & FOLL_WRITE);
        bool write = vmf->flags & FAULT_FLAG_WRITE;

so I'll go for just "write".

Thanks,

Paolo