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Date: Tue, 25 Oct 2016 03:13:09 +0300 From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> To: "Theodore Ts'o" <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Jan Kara <jack@...e.com>, Andrew Morton <akpm@...ux-foundation.org> Cc: Alexander Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Dave Hansen <dave.hansen@...el.com>, Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>, Ross Zwisler <ross.zwisler@...ux.intel.com>, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-block@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: [PATCHv4 10/43] thp: try to free page's buffers before attempt split We want page to be isolated from the rest of the system before spliting 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 <kirill.shutemov@...ux.intel.com> --- 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 ebbacd14d450..006a8a42acfb 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -395,6 +395,7 @@ 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 e7cda8e86f2c..40fe91ac383c 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> @@ -2066,7 +2067,6 @@ 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)) { @@ -2095,6 +2095,23 @@ 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; -- 2.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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