linux-kernel - [PATCH 06/11] iomap: Support THPs in invalidatepage

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Date:   Mon, 24 Aug 2020 16:16:55 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-block@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 06/11] iomap: Support THPs in invalidatepage

If we're punching a hole in a THP, we need to remove the per-page
iomap data as the THP is about to be split and each page will need
its own.  This means that writepage can now come across a page with
no iop allocated, so remove the assertions that there is already one,
and just create one (with the Uptodate bits set) if there isn't one.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/iomap/buffered-io.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 5cc0343b6a8e..9ea162617398 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -54,6 +54,8 @@ iomap_page_create(struct inode *inode, struct page *page)
 	iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
 			GFP_NOFS | __GFP_NOFAIL);
 	spin_lock_init(&iop->uptodate_lock);
+	if (PageUptodate(page))
+		bitmap_fill(iop->uptodate, nr_blocks);
 	attach_page_private(page, iop);
 	return iop;
 }
@@ -483,10 +485,17 @@ iomap_invalidatepage(struct page *page, unsigned int offset, unsigned int len)
 	 * If we are invalidating the entire page, clear the dirty state from it
 	 * and release it to avoid unnecessary buildup of the LRU.
 	 */
-	if (offset == 0 && len == PAGE_SIZE) {
+	if (offset == 0 && len == thp_size(page)) {
 		WARN_ON_ONCE(PageWriteback(page));
 		cancel_dirty_page(page);
 		iomap_page_release(page);
+		return;
+	}
+
+	/* Punching a hole in a THP requires releasing the iop */
+	if (PageTransHuge(page)) {
+		VM_BUG_ON_PAGE(!PageUptodate(page), page);
+		iomap_page_release(page);
 	}
 }
 EXPORT_SYMBOL_GPL(iomap_invalidatepage);
@@ -1043,14 +1052,13 @@ static void
 iomap_finish_page_writeback(struct inode *inode, struct page *page,
 		int error, unsigned int len)
 {
-	struct iomap_page *iop = to_iomap_page(page);
+	struct iomap_page *iop = iomap_page_create(inode, page);
 
 	if (error) {
 		SetPageError(page);
 		mapping_set_error(inode->i_mapping, -EIO);
 	}
 
-	WARN_ON_ONCE(i_blocks_per_page(inode, page) > 1 && !iop);
 	WARN_ON_ONCE(iop && atomic_read(&iop->write_count) <= 0);
 
 	if (!iop || atomic_sub_and_test(len, &iop->write_count))
@@ -1340,14 +1348,13 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
 		struct writeback_control *wbc, struct inode *inode,
 		struct page *page, u64 end_offset)
 {
-	struct iomap_page *iop = to_iomap_page(page);
+	struct iomap_page *iop = iomap_page_create(inode, page);
 	struct iomap_ioend *ioend, *next;
 	unsigned len = i_blocksize(inode);
 	u64 file_offset; /* file offset of page */
 	int error = 0, count = 0, i;
 	LIST_HEAD(submit_list);
 
-	WARN_ON_ONCE(i_blocks_per_page(inode, page) > 1 && !iop);
 	WARN_ON_ONCE(iop && atomic_read(&iop->write_count) != 0);
 
 	/*
-- 
2.28.0