[PATCHv6 05/37] thp: try to free page's buffers before attempt split
From: Kirill A. Shutemov <hidden>
Date: 2017-01-26 11:57:47
Also in:
linux-ext4, linux-fsdevel, linux-mm, lkml
Subsystem:
memory management, memory management - thp (transparent huge page), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds
We want page to be isolated from the rest of the system before splitting it. We rely on page count to be 2 for file pages to make sure nobody uses the page: one pin to caller, one to radix-tree. Filesystems with backing storage can have page count increased if it has buffers. Let's try to free them, before attempt split. And remove one guarding VM_BUG_ON_PAGE(). Signed-off-by: Kirill A. Shutemov <redacted> --- include/linux/buffer_head.h | 1 + mm/huge_memory.c | 19 ++++++++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index d67ab83823ad..fd4134ce9c54 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h@@ -400,6 +400,7 @@ extern int __set_page_dirty_buffers(struct page *page); #else /* CONFIG_BLOCK */ static inline void buffer_init(void) {} +static inline int page_has_buffers(struct page *page) { return 0; } static inline int try_to_free_buffers(struct page *page) { return 1; } static inline int inode_has_buffers(struct inode *inode) { return 0; } static inline void invalidate_inode_buffers(struct inode *inode) {}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 89819fe4debc..55aee62e8444 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -30,6 +30,7 @@ #include <linux/userfaultfd_k.h> #include <linux/page_idle.h> #include <linux/shmem_fs.h> +#include <linux/buffer_head.h> #include <asm/tlb.h> #include <asm/pgalloc.h>
@@ -2117,7 +2118,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) VM_BUG_ON_PAGE(is_huge_zero_page(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page); - VM_BUG_ON_PAGE(!PageSwapBacked(page), page); VM_BUG_ON_PAGE(!PageCompound(page), page); if (PageAnon(head)) {
@@ -2146,6 +2146,23 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) goto out; } + /* Try to free buffers before attempt split */ + if (!PageSwapBacked(head) && PagePrivate(page)) { + /* + * We cannot trigger writeback from here due possible + * recursion if triggered from vmscan, only wait. + * + * Caller can trigger writeback it on its own, if safe. + */ + wait_on_page_writeback(head); + + if (page_has_buffers(head) && !try_to_release_page(head, + GFP_KERNEL)) { + ret = -EBUSY; + goto out; + } + } + /* Addidional pin from radix tree */ extra_pins = 1; anon_vma = NULL;
--
2.11.0