Re: [PATCHv6 05/37] thp: try to free page's buffers before attempt split
From: Matthew Wilcox <willy@infradead.org>
Date: 2017-02-09 20:14:16
Also in:
linux-ext4, linux-fsdevel, linux-mm, lkml
On Thu, Jan 26, 2017 at 02:57:47PM +0300, Kirill A. Shutemov wrote:
quoted hunk ↗ jump to hunk
@@ -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. + */
It took me a few reads to get this. May I suggest: /* * Cannot split a page with buffers. If the caller has * already started writeback, we can wait for it to finish, * but we cannot start writeback if we were called from vmscan */
+ if (!PageSwapBacked(head) && PagePrivate(page)) {Also, it looks weird to test PageSwapBacked of *head* and PagePrivate of *page*. I think it's correct, but it still looks weird. Reviewed-by: Matthew Wilcox <redacted>