+ mm-filemap-change-filemap_create_page-calling-conventions.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/filemap: change filemap_create_page calling conventions
has been added to the -mm tree.  Its filename is
     mm-filemap-change-filemap_create_page-calling-conventions.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-filemap-change-filemap_create_page-calling-conventions.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-filemap-change-filemap_create_page-calling-conventions.patch

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: 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.

Link: https://lkml.kernel.org/r/20210122160140.223228-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/filemap.c |   53 ++++++++++++++++++++++++-------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

--- a/mm/filemap.c~mm-filemap-change-filemap_create_page-calling-conventions
+++ a/mm/filemap.c
@@ -2284,32 +2284,33 @@ truncated:
 	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,
@@ -2337,15 +2338,15 @@ find_page:
 	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];
_

Patches currently in -mm which might be from willy@infradead.org are

mm-debug-improve-memcg-debugging.patch
mm-filemap-rename-generic_file_buffered_read-subfunctions.patch
mm-filemap-remove-dynamically-allocated-array-from-filemap_read.patch
mm-filemap-convert-filemap_get_pages-to-take-a-pagevec.patch
mm-filemap-use-head-pages-in-generic_file_buffered_read.patch
mm-filemap-pass-a-sleep-state-to-put_and_wait_on_page_locked.patch
mm-filemap-support-readpage-splitting-a-page.patch
mm-filemap-inline-__wait_on_page_locked_async-into-caller.patch
mm-filemap-dont-call-readpage-if-iocb_waitq-is-set.patch
mm-filemap-change-filemap_read_page-calling-conventions.patch
mm-filemap-change-filemap_create_page-calling-conventions.patch
mm-filemap-convert-filemap_update_page-to-return-an-errno.patch
mm-filemap-move-the-iocb-checks-into-filemap_update_page.patch
mm-filemap-add-filemap_range_uptodate.patch
mm-filemap-split-filemap_readahead-out-of-filemap_get_pages.patch
mm-filemap-restructure-filemap_get_pages.patch
mm-filemap-dont-relock-the-page-after-calling-readpage.patch
mm-make-pagecache-tagged-lookups-return-only-head-pages.patch
mm-shmem-use-pagevec_lookup-in-shmem_unlock_mapping.patch
mm-swap-optimise-get_shadow_from_swap_cache.patch
mm-add-fgp_entry.patch
mm-filemap-rename-find_get_entry-to-mapping_get_entry.patch
mm-filemap-add-helper-for-finding-pages.patch
mm-filemap-add-helper-for-finding-pages-fix.patch
mm-filemap-add-mapping_seek_hole_data.patch
mm-filemap-add-mapping_seek_hole_data-fix.patch
iomap-use-mapping_seek_hole_data.patch
mm-add-and-use-find_lock_entries.patch
mm-add-and-use-find_lock_entries-fix.patch
mm-add-an-end-parameter-to-find_get_entries.patch
mm-add-an-end-parameter-to-pagevec_lookup_entries.patch
mm-remove-nr_entries-parameter-from-pagevec_lookup_entries.patch
mm-pass-pvec-directly-to-find_get_entries.patch
mm-remove-pagevec_lookup_entries.patch