mm: consistently use current->mm in mm_get_unmapped_area()

mm_get_unmapped_area() is a wrapper around arch_get_unmapped_area() /
arch_get_unmapped_area_topdown(), both of which search current->mm for
some free space. Neither take an mm_struct - they implicitly operate on
current->mm.

But the wrapper takes an mm_struct and uses it to decide whether to search
bottom up or top down. All callers pass in current->mm for this, so
everything is working consistently. But it feels like an accident waiting
to happen; eventually someone will call that function with a different mm,
expecting to find free space in it, but what gets returned is free space
in the current mm.

So let's simplify by removing the parameter and have the wrapper use
current->mm to decide which end to start at. Now everything is consistent
and self-documenting.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ryan Roberts <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Reviewed-by: Oscar Salvador <[e-mail]>
Reviewed-by: Dev Jain <[e-mail]>
Reviewed-by: Anshuman Khandual <[e-mail]>
Reviewed-by: Lorenzo Stoakes <[e-mail]>
Reviewed-by: Baolin Wang <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Suren Baghdasaryan <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/sparc/kernel/sys_sparc_64.c

···
 
 	if (flags & MAP_FIXED) {
 		/* Ok, don't mess with it. */
-		return mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags);
+		return mm_get_unmapped_area(NULL, orig_addr, len, pgoff, flags);
 	}
 	flags &= ~MAP_SHARED;
 
···
 		align_goal = (64UL * 1024);
 
 	do {
-		addr = mm_get_unmapped_area(current->mm, NULL, orig_addr,
+		addr = mm_get_unmapped_area(NULL, orig_addr,
 					    len + (align_goal - PAGE_SIZE), pgoff, flags);
 		if (!(addr & ~PAGE_MASK)) {
 			addr = (addr + (align_goal - 1UL)) & ~(align_goal - 1UL);
···
 	 * be obtained.
 	 */
 	if (addr & ~PAGE_MASK)
-		addr = mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags);
+		addr = mm_get_unmapped_area(NULL, orig_addr, len, pgoff, flags);
 
 	return addr;
 }

arch/x86/kernel/cpu/sgx/driver.c

···
 	if (flags & MAP_FIXED)
 		return addr;
 
-	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(file, addr, len, pgoff, flags);
 }
 
 #ifdef CONFIG_COMPAT

drivers/char/mem.c

···
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	return thp_get_unmapped_area(file, addr, len, pgoff, flags);
 #else
-	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(file, addr, len, pgoff, flags);
 #endif
 }
 #endif /* CONFIG_MMU */

drivers/dax/device.c

···
 	if ((off + len_align) < off)
 		goto out;
 
-	addr_align = mm_get_unmapped_area(current->mm, filp, addr, len_align,
-					  pgoff, flags);
+	addr_align = mm_get_unmapped_area(filp, addr, len_align, pgoff, flags);
 	if (!IS_ERR_VALUE(addr_align)) {
 		addr_align += (off - addr_align) & (align - 1);
 		return addr_align;
 	}
  out:
-	return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(filp, addr, len, pgoff, flags);
 }
 
 static const struct address_space_operations dev_dax_aops = {

fs/hugetlbfs/inode.c

···
 	if (addr)
 		addr0 = ALIGN(addr, huge_page_size(h));
 
-	return mm_get_unmapped_area_vmflags(current->mm, file, addr0, len, pgoff,
-					    flags, 0);
+	return mm_get_unmapped_area_vmflags(file, addr0, len, pgoff, flags, 0);
 }
 
 /*

fs/proc/inode.c

···
 		return pde->proc_ops->proc_get_unmapped_area(file, orig_addr, len, pgoff, flags);
 
 #ifdef CONFIG_MMU
-	return mm_get_unmapped_area(current->mm, file, orig_addr, len, pgoff, flags);
+	return mm_get_unmapped_area(file, orig_addr, len, pgoff, flags);
 #endif
 
 	return orig_addr;

fs/ramfs/file-mmu.c

···
 		unsigned long addr, unsigned long len, unsigned long pgoff,
 		unsigned long flags)
 {
-	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(file, addr, len, pgoff, flags);
 }
 
 const struct file_operations ramfs_file_operations = {

include/linux/sched/mm.h

···
 			       unsigned long len, unsigned long pgoff,
 			       unsigned long flags, vm_flags_t);
 
-unsigned long mm_get_unmapped_area(struct mm_struct *mm, struct file *filp,
-				   unsigned long addr, unsigned long len,
-				   unsigned long pgoff, unsigned long flags);
+unsigned long mm_get_unmapped_area(struct file *filp, unsigned long addr,
+				   unsigned long len, unsigned long pgoff,
+				   unsigned long flags);
 
-unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm,
-					   struct file *filp,
+unsigned long mm_get_unmapped_area_vmflags(struct file *filp,
 					   unsigned long addr,
 					   unsigned long len,
 					   unsigned long pgoff,

io_uring/memmap.c

···
 #else
 	addr = 0UL;
 #endif
-	return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(filp, addr, len, pgoff, flags);
 }
 
 #else /* !CONFIG_MMU */

kernel/bpf/arena.c

···
 			return -EINVAL;
 	}
 
-	ret = mm_get_unmapped_area(current->mm, filp, addr, len * 2, 0, flags);
+	ret = mm_get_unmapped_area(filp, addr, len * 2, 0, flags);
 	if (IS_ERR_VALUE(ret))
 		return ret;
 	if ((ret >> 32) == ((ret + len - 1) >> 32))

kernel/bpf/syscall.c

···
 	if (map->ops->map_get_unmapped_area)
 		return map->ops->map_get_unmapped_area(filp, addr, len, pgoff, flags);
 #ifdef CONFIG_MMU
-	return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(filp, addr, len, pgoff, flags);
 #else
 	return addr;
 #endif

mm/huge_memory.c

···
 	if (len_pad < len || (off + len_pad) < off)
 		return 0;
 
-	ret = mm_get_unmapped_area_vmflags(current->mm, filp, addr, len_pad,
+	ret = mm_get_unmapped_area_vmflags(filp, addr, len_pad,
 					   off >> PAGE_SHIFT, flags, vm_flags);
 
 	/*
···
 	if (ret)
 		return ret;
 
-	return mm_get_unmapped_area_vmflags(current->mm, filp, addr, len, pgoff, flags,
+	return mm_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags,
 					    vm_flags);
 }
 

mm/mmap.c

···
 }
 #endif
 
-unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, struct file *filp,
-					   unsigned long addr, unsigned long len,
-					   unsigned long pgoff, unsigned long flags,
-					   vm_flags_t vm_flags)
+unsigned long mm_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
+					   unsigned long len, unsigned long pgoff,
+					   unsigned long flags, vm_flags_t vm_flags)
 {
-	if (mm_flags_test(MMF_TOPDOWN, mm))
+	if (mm_flags_test(MMF_TOPDOWN, current->mm))
 		return arch_get_unmapped_area_topdown(filp, addr, len, pgoff,
 						      flags, vm_flags);
 	return arch_get_unmapped_area(filp, addr, len, pgoff, flags, vm_flags);
···
 		addr = thp_get_unmapped_area_vmflags(file, addr, len,
 						     pgoff, flags, vm_flags);
 	} else {
-		addr = mm_get_unmapped_area_vmflags(current->mm, file, addr, len,
+		addr = mm_get_unmapped_area_vmflags(file, addr, len,
 						    pgoff, flags, vm_flags);
 	}
 	if (IS_ERR_VALUE(addr))
···
 }
 
 unsigned long
-mm_get_unmapped_area(struct mm_struct *mm, struct file *file,
-		     unsigned long addr, unsigned long len,
+mm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 		     unsigned long pgoff, unsigned long flags)
 {
-	return mm_get_unmapped_area_vmflags(mm, file, addr, len,
-					    pgoff, flags, 0);
+	return mm_get_unmapped_area_vmflags(file, addr, len, pgoff, flags, 0);
 }
 EXPORT_SYMBOL(mm_get_unmapped_area);
 

mm/shmem.c

···
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
-	addr = mm_get_unmapped_area(current->mm, file, uaddr, len, pgoff,
-				    flags);
+	addr = mm_get_unmapped_area(file, uaddr, len, pgoff, flags);
 
 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
 		return addr;
···
 	if (inflated_len < len)
 		return addr;
 
-	inflated_addr = mm_get_unmapped_area(current->mm, NULL, uaddr,
-					     inflated_len, 0, flags);
+	inflated_addr = mm_get_unmapped_area(NULL, uaddr, inflated_len, 0, flags);
 	if (IS_ERR_VALUE(inflated_addr))
 		return addr;
 	if (inflated_addr & ~PAGE_MASK)
···
 				      unsigned long addr, unsigned long len,
 				      unsigned long pgoff, unsigned long flags)
 {
-	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
+	return mm_get_unmapped_area(file, addr, len, pgoff, flags);
 }
 #endif