linux-kernel - Re: [RFC PATCH v3 09/10] mm: create __do_mmap() to take an mm

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Message-ID: <c9a7444b-4b3b-4203-9d1d-8b6ded9ac1a9@oracle.com>
Date: Mon, 7 Oct 2024 10:46:41 -0700
From: Anthony Yznaga <anthony.yznaga@...cle.com>
To: "Kirill A. Shutemov" <kirill@...temov.name>
Cc: akpm@...ux-foundation.org, willy@...radead.org, markhemm@...glemail.com,
        viro@...iv.linux.org.uk, david@...hat.com, khalid@...nel.org,
        andreyknvl@...il.com, dave.hansen@...el.com, luto@...nel.org,
        brauner@...nel.org, arnd@...db.de, ebiederm@...ssion.com,
        catalin.marinas@....com, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhiramat@...nel.org,
        rostedt@...dmis.org, vasily.averin@...ux.dev, xhao@...ux.alibaba.com,
        pcc@...gle.com, neilb@...e.de, maz@...nel.org
Subject: Re: [RFC PATCH v3 09/10] mm: create __do_mmap() to take an mm_struct
 * arg


On 10/7/24 1:44 AM, Kirill A. Shutemov wrote:
> On Tue, Sep 03, 2024 at 04:22:40PM -0700, Anthony Yznaga wrote:
>> In preparation for mapping objects into an mshare region, create
>> __do_mmap() to allow mapping into a specified mm. There are no
>> functional changes otherwise.
>>
>> Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
>> ---
>>   include/linux/mm.h | 18 +++++++++++++++++-
>>   mm/mmap.c          | 12 +++++-------
>>   2 files changed, 22 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 3aa0b3322284..a9afbda73cb0 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -3409,11 +3409,27 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
>>   
>>   extern unsigned long mmap_region(struct file *file, unsigned long addr,
>>   	unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
>> -	struct list_head *uf);
>> +	struct list_head *uf, struct mm_struct *mm);
>> +#ifdef CONFIG_MMU
>> +extern unsigned long __do_mmap(struct file *file, unsigned long addr,
>> +	unsigned long len, unsigned long prot, unsigned long flags,
>> +	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
>> +	struct list_head *uf, struct mm_struct *mm);
>> +static inline unsigned long do_mmap(struct file *file, unsigned long addr,
>> +	unsigned long len, unsigned long prot, unsigned long flags,
>> +	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
>> +	struct list_head *uf)
>> +{
>> +	return __do_mmap(file, addr, len, prot, flags, vm_flags, pgoff,
>> +			 populate, uf, current->mm);
>> +}
>> +#else
>>   extern unsigned long do_mmap(struct file *file, unsigned long addr,
>>   	unsigned long len, unsigned long prot, unsigned long flags,
>>   	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
>>   	struct list_head *uf);
>> +#endif
>> +
>>   extern int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
>>   			 unsigned long start, size_t len, struct list_head *uf,
>>   			 bool unlock);
>> diff --git a/mm/mmap.c b/mm/mmap.c
>> index d0dfc85b209b..4112f18e7302 100644
>> --- a/mm/mmap.c
>> +++ b/mm/mmap.c
>> @@ -1250,15 +1250,14 @@ static inline bool file_mmap_ok(struct file *file, struct inode *inode,
>>   }
>>   
>>   /*
>> - * The caller must write-lock current->mm->mmap_lock.
>> + * The caller must write-lock mm->mmap_lock.
>>    */
>> -unsigned long do_mmap(struct file *file, unsigned long addr,
>> +unsigned long __do_mmap(struct file *file, unsigned long addr,
>>   			unsigned long len, unsigned long prot,
>>   			unsigned long flags, vm_flags_t vm_flags,
>>   			unsigned long pgoff, unsigned long *populate,
>> -			struct list_head *uf)
>> +			struct list_head *uf, struct mm_struct *mm)
> Argument list getting too long. At some point we need to have a struct to
> pass them around.

I'll look into doing that.


Anthony

>
>>   {
>> -	struct mm_struct *mm = current->mm;
>>   	int pkey = 0;
>>   
>>   	*populate = 0;
>> @@ -1465,7 +1464,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
>>   			vm_flags |= VM_NORESERVE;
>>   	}
>>   
>> -	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
>> +	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf, mm);
>>   	if (!IS_ERR_VALUE(addr) &&
>>   	    ((vm_flags & VM_LOCKED) ||
>>   	     (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
>> @@ -2848,9 +2847,8 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
>>   
>>   unsigned long mmap_region(struct file *file, unsigned long addr,
>>   		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
>> -		struct list_head *uf)
>> +		struct list_head *uf, struct mm_struct *mm)
>>   {
>> -	struct mm_struct *mm = current->mm;
>>   	struct vm_area_struct *vma = NULL;
>>   	struct vm_area_struct *next, *prev, *merge;
>>   	pgoff_t pglen = len >> PAGE_SHIFT;
>> -- 
>> 2.43.5
>>