[9/9] Documentation/mm: update hugetlbfs documentation to mention alloc_hugetlb_folio
Commit Message
alloc_huge_page() has been renamed to alloc_hugetlb_folio() so update the
documentation which mentions alloc_huge_page(). Subpool information has
been moved from page->private to having a dedicated field in struct folio,
reflect this in the documentation.
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---
Documentation/mm/hugetlbfs_reserv.rst | 21 ++++++++++---------
.../zh_CN/mm/hugetlbfs_reserv.rst | 14 ++++++-------
2 files changed, 18 insertions(+), 17 deletions(-)
@@ -181,14 +181,14 @@ Consuming Reservations/Allocating a Huge Page
Reservations are consumed when huge pages associated with the reservations
are allocated and instantiated in the corresponding mapping. The allocation
-is performed within the routine alloc_huge_page()::
+is performed within the routine alloc_hugetlb_folio()::
- struct page *alloc_huge_page(struct vm_area_struct *vma,
+ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve)
-alloc_huge_page is passed a VMA pointer and a virtual address, so it can
+alloc_hugetlb_folio is passed a VMA pointer and a virtual address, so it can
consult the reservation map to determine if a reservation exists. In addition,
-alloc_huge_page takes the argument avoid_reserve which indicates reserves
+alloc_hugetlb_folio takes the argument avoid_reserve which indicates reserves
should not be used even if it appears they have been set aside for the
specified address. The avoid_reserve argument is most often used in the case
of Copy on Write and Page Migration where additional copies of an existing
@@ -208,7 +208,8 @@ a reservation for the allocation. After determining whether a reservation
exists and can be used for the allocation, the routine dequeue_huge_page_vma()
is called. This routine takes two arguments related to reservations:
-- avoid_reserve, this is the same value/argument passed to alloc_huge_page()
+- avoid_reserve, this is the same value/argument passed to
+ alloc_hugetlb_folio().
- chg, even though this argument is of type long only the values 0 or 1 are
passed to dequeue_huge_page_vma. If the value is 0, it indicates a
reservation exists (see the section "Memory Policy and Reservations" for
@@ -233,9 +234,9 @@ the scope reservations. Even if a surplus page is allocated, the same
reservation based adjustments as above will be made: SetPagePrivate(page) and
resv_huge_pages--.
-After obtaining a new huge page, (page)->private is set to the value of
-the subpool associated with the page if it exists. This will be used for
-subpool accounting when the page is freed.
+After obtaining a new hugetlb folio, (folio)->_hugetlb_subpool is set to the
+value of the subpool associated with the page if it exists. This will be used
+for subpool accounting when the folio is freed.
The routine vma_commit_reservation() is then called to adjust the reserve
map based on the consumption of the reservation. In general, this involves
@@ -246,8 +247,8 @@ was no reservation in a shared mapping or this was a private mapping a new
entry must be created.
It is possible that the reserve map could have been changed between the call
-to vma_needs_reservation() at the beginning of alloc_huge_page() and the
-call to vma_commit_reservation() after the page was allocated. This would
+to vma_needs_reservation() at the beginning of alloc_hugetlb_folio() and the
+call to vma_commit_reservation() after the folio was allocated. This would
be possible if hugetlb_reserve_pages was called for the same page in a shared
mapping. In such cases, the reservation count and subpool free page count
will be off by one. This rare condition can be identified by comparing the
@@ -142,14 +142,14 @@ HPAGE_RESV_OWNER标志被设置，以表明该VMA拥有预留。
消耗预留/分配一个巨页
===========================
-当与预留相关的巨页在相应的映射中被分配和实例化时，预留就被消耗了。该分配是在函数alloc_huge_page()
+当与预留相关的巨页在相应的映射中被分配和实例化时，预留就被消耗了。该分配是在函数alloc_hugetlb_folio()
中进行的::
- struct page *alloc_huge_page(struct vm_area_struct *vma,
+ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve)
-alloc_huge_page被传递给一个VMA指针和一个虚拟地址，因此它可以查阅预留映射以确定是否存在预留。
-此外，alloc_huge_page需要一个参数avoid_reserve，该参数表示即使看起来已经为指定的地址预留了
+alloc_hugetlb_folio被传递给一个VMA指针和一个虚拟地址，因此它可以查阅预留映射以确定是否存在预留。
+此外，alloc_hugetlb_folio需要一个参数avoid_reserve，该参数表示即使看起来已经为指定的地址预留了
预留，也不应该使用预留。avoid_reserve参数最常被用于写时拷贝和页面迁移的情况下，即现有页面的额
外拷贝被分配。
@@ -162,7 +162,7 @@ vma_needs_reservation()返回的值通常为0或1。如果该地址存在预留
确定预留是否存在并可用于分配后，调用dequeue_huge_page_vma()函数。这个函数需要两个与预留有关
的参数：
-- avoid_reserve，这是传递给alloc_huge_page()的同一个值/参数。
+- avoid_reserve，这是传递给alloc_hugetlb_folio()的同一个值/参数。
- chg，尽管这个参数的类型是long，但只有0或1的值被传递给dequeue_huge_page_vma。如果该值为0，
则表明存在预留（关于可能的问题，请参见 “预留和内存策略” 一节）。如果值
为1，则表示不存在预留，如果可能的话，必须从全局空闲池中取出该页。
@@ -179,7 +179,7 @@ free_huge_pages的值被递减。如果有一个与该页相关的预留，将
的剩余巨页和超额分配的问题。即使分配了一个多余的页面，也会进行与上面一样的基于预留的调整:
SetPagePrivate(page) 和 resv_huge_pages--.
-在获得一个新的巨页后，(page)->private被设置为与该页面相关的子池的值，如果它存在的话。当页
+在获得一个新的巨页后，(folio)->_hugetlb_subpool被设置为与该页面相关的子池的值，如果它存在的话。当页
面被释放时，这将被用于子池的计数。
然后调用函数vma_commit_reservation()，根据预留的消耗情况调整预留映射。一般来说，这涉及
@@ -199,7 +199,7 @@ SetPagePrivate(page)和resv_huge_pages-。
已经存在，所以不做任何改变。然而，如果共享映射中没有预留，或者这是一个私有映射，则必须创建
一个新的条目。
-在alloc_huge_page()开始调用vma_needs_reservation()和页面分配后调用
+在alloc_hugetlb_folio()开始调用vma_needs_reservation()和页面分配后调用
vma_commit_reservation()之间，预留映射有可能被改变。如果hugetlb_reserve_pages在共
享映射中为同一页面被调用，这将是可能的。在这种情况下，预留计数和子池空闲页计数会有一个偏差。
这种罕见的情况可以通过比较vma_needs_reservation和vma_commit_reservation的返回值来