[bug report] mm: avoid leaving partial pfn mappings around in error case

[Dan Carpenter <dan.carpenter@linaro.org>]

Hi Linus,

Commit 79a61cc3fc04 ("mm: avoid leaving partial pfn mappings around in
error case") from Sep 11, 2024 (linux-next), leads to the following
Smatch static checker warning:

	mm/memory.c:2709 remap_pfn_range_notrack()
	warn: sleeping in atomic context

mm/memory.c
    2696 int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
    2697                 unsigned long pfn, unsigned long size, pgprot_t prot)
    2698 {
    2699         int error = remap_pfn_range_internal(vma, addr, pfn, size, prot);
    2700 
    2701         if (!error)
    2702                 return 0;
    2703 
    2704         /*
    2705          * A partial pfn range mapping is dangerous: it does not
    2706          * maintain page reference counts, and callers may free
    2707          * pages due to the error. So zap it early.
    2708          */
--> 2709         zap_page_range_single(vma, addr, size, NULL);

The lru_add_drain() function at the start of zap_page_range_single() takes a
mutext.

    2710         return error;
    2711 }

It's the preempt_disable() in gru_fault() which is the issue.  The call tree
is:

gru_fault() <- disables preempt
-> remap_pfn_range()
   -> remap_pfn_range_notrack()

regards,
dan carpenter