mm/mempolicy: rewrite alloc_pages_vma documentation

mainline inclusion
from mainline-5.13-rc1
commit eb350739
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZVL2
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eb35073960510762dee417574589b7a8971c68ab

-------------------------------------------------

The current formatting doesn't quite work with kernel-doc.

Link: https://lkml.kernel.org/r/20210225150642.2582252-7-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: NMike Rapoport <rppt@linux.ibm.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit eb350739)
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>
Reviewed-by: NTong Tiangen <tongtiangen@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/mempolicy.c

@@ -2147,30 +2147,22 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
 }
 
 /**
- * 	alloc_pages_vma	- Allocate a page for a VMA.
- *
- * 	@gfp:
- *      %GFP_USER    user allocation.
- *      %GFP_KERNEL  kernel allocations,
- *      %GFP_HIGHMEM highmem/user allocations,
- *      %GFP_FS      allocation should not call back into a file system.
- *      %GFP_ATOMIC  don't sleep.
+ * alloc_pages_vma - Allocate a page for a VMA.
+ * @gfp: GFP flags.
+ * @order: Order of the GFP allocation.
+ * @vma: Pointer to VMA or NULL if not available.
+ * @addr: Virtual address of the allocation.  Must be inside @vma.
+ * @node: Which node to prefer for allocation (modulo policy).
+ * @hugepage: For hugepages try only the preferred node if possible.
  *
- *	@order:Order of the GFP allocation.
- * 	@vma:  Pointer to VMA or NULL if not available.
- *	@addr: Virtual Address of the allocation. Must be inside the VMA.
- *	@node: Which node to prefer for allocation (modulo policy).
- *	@hugepage: for hugepages try only the preferred node if possible
+ * Allocate a page for a specific address in @vma, using the appropriate
+ * NUMA policy.  When @vma is not NULL the caller must hold the mmap_lock
+ * of the mm_struct of the VMA to prevent it from going away.  Should be
+ * used for all allocations for pages that will be mapped into user space.
  *
- * 	This function allocates a page from the kernel page pool and applies
- *	a NUMA policy associated with the VMA or the current process.
- *	When VMA is not NULL caller must read-lock the mmap_lock of the
- *	mm_struct of the VMA to prevent it from going away. Should be used for
- *	all allocations for pages that will be mapped into user space. Returns
- *	NULL when no page can be allocated.
+ * Return: The page on success or NULL if allocation fails.
  */
-struct page *
-alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
+struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 		unsigned long addr, int node, bool hugepage)
 {
 	struct mempolicy *pol;