linux-kernel - [PATCH v5 10/18] mm/filemap: Change filemap_create

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Message-Id: <20210122160140.223228-11-willy@infradead.org>
Date:   Fri, 22 Jan 2021 16:01:32 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Kent Overstreet <kent.overstreet@...il.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH v5 10/18] mm/filemap: Change filemap_create_page calling conventions

By moving the iocb flag checks to the caller, we can pass the
file and the page index instead of the iocb.  It never needed the iter.
By passing the pagevec, we can return an errno (or AOP_TRUNCATED_PAGE)
instead of an ERR_PTR.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@...il.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 mm/filemap.c | 53 ++++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index ceb2931f5725f..3e0790626addf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2303,32 +2303,33 @@ static struct page *filemap_update_page(struct kiocb *iocb, struct file *filp,
 	return NULL;
 }
 
-static struct page *filemap_create_page(struct kiocb *iocb,
-		struct iov_iter *iter)
+static int filemap_create_page(struct file *file,
+		struct address_space *mapping, pgoff_t index,
+		struct pagevec *pvec)
 {
-	struct file *filp = iocb->ki_filp;
-	struct address_space *mapping = filp->f_mapping;
-	pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
 	struct page *page;
 	int error;
 
-	if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
-		return ERR_PTR(-EAGAIN);
-
 	page = page_cache_alloc(mapping);
 	if (!page)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	error = add_to_page_cache_lru(page, mapping, index,
-				      mapping_gfp_constraint(mapping, GFP_KERNEL));
-	if (!error)
-		error = filemap_read_page(iocb->ki_filp, mapping, page);
-	if (!error)
-		return page;
+			mapping_gfp_constraint(mapping, GFP_KERNEL));
+	if (error == -EEXIST)
+		error = AOP_TRUNCATED_PAGE;
+	if (error)
+		goto error;
+
+	error = filemap_read_page(file, mapping, page);
+	if (error)
+		goto error;
+
+	pagevec_add(pvec, page);
+	return 0;
+error:
 	put_page(page);
-	if (error == -EEXIST || error == AOP_TRUNCATED_PAGE)
-		return NULL;
-	return ERR_PTR(error);
+	return error;
 }
 
 static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
@@ -2356,15 +2357,15 @@ static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
 	page_cache_sync_readahead(mapping, ra, filp, index, last_index - index);
 
 	filemap_get_read_batch(mapping, index, last_index, pvec);
-	if (pvec->nr)
-		goto got_pages;
-
-	pvec->pages[0] = filemap_create_page(iocb, iter);
-	err = PTR_ERR_OR_ZERO(pvec->pages[0]);
-	if (IS_ERR_OR_NULL(pvec->pages[0]))
-		goto err;
-	pvec->nr = 1;
-	return 0;
+	if (!pagevec_count(pvec)) {
+		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
+			return -EAGAIN;
+		err = filemap_create_page(filp, mapping,
+				iocb->ki_pos >> PAGE_SHIFT, pvec);
+		if (err == AOP_TRUNCATED_PAGE)
+			goto find_page;
+		return err;
+	}
 got_pages:
 	{
 		struct page *page = pvec->pages[pvec->nr - 1];
-- 
2.29.2