From:   "Matthew Wilcox (Oracle)" <willy@infradead.org>
To:     "Theodore Tso" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>
Cc:     "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 01/31] fs: Add FGP_WRITEBEGIN
Date:   Thu, 26 Jan 2023 20:23:45 +0000
Message-Id: <20230126202415.1682629-2-willy@infradead.org>
In-Reply-To: <20230126202415.1682629-1-willy@infradead.org>
References: <20230126202415.1682629-1-willy@infradead.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

This particular combination of flags is used by most filesystems
in their ->write_begin method, although it does find use in a
few other places.  Before folios, it warranted its own function
(grab_cache_page_write_begin()), but I think that just having specialised
flags is enough.  It certainly helps the few places that have been
converted from grab_cache_page_write_begin() to __filemap_get_folio().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/ext4/move_extent.c    | 5 ++---
 fs/iomap/buffered-io.c   | 2 +-
 fs/netfs/buffered_read.c | 3 +--
 include/linux/pagemap.h  | 2 ++
 mm/folio-compat.c        | 4 +---
 5 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 2de9829aed63..0cb361f0a4fe 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -126,7 +126,6 @@ mext_folio_double_lock(struct inode *inode1, struct inode *inode2,
 {
 	struct address_space *mapping[2];
 	unsigned int flags;
-	unsigned fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE;
 
 	BUG_ON(!inode1 || !inode2);
 	if (inode1 < inode2) {
@@ -139,14 +138,14 @@ mext_folio_double_lock(struct inode *inode1, struct inode *inode2,
 	}
 
 	flags = memalloc_nofs_save();
-	folio[0] = __filemap_get_folio(mapping[0], index1, fgp_flags,
+	folio[0] = __filemap_get_folio(mapping[0], index1, FGP_WRITEBEGIN,
 			mapping_gfp_mask(mapping[0]));
 	if (!folio[0]) {
 		memalloc_nofs_restore(flags);
 		return -ENOMEM;
 	}
 
-	folio[1] = __filemap_get_folio(mapping[1], index2, fgp_flags,
+	folio[1] = __filemap_get_folio(mapping[1], index2, FGP_WRITEBEGIN,
 			mapping_gfp_mask(mapping[1]));
 	memalloc_nofs_restore(flags);
 	if (!folio[1]) {
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 6f4c97a6d7e9..10a203515583 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -467,7 +467,7 @@ EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
  */
 struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos)
 {
-	unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
+	unsigned fgp = FGP_WRITEBEGIN | FGP_NOFS;
 	struct folio *folio;
 
 	if (iter->flags & IOMAP_NOWAIT)
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 7679a68e8193..e3d754a9e1b0 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -341,14 +341,13 @@ int netfs_write_begin(struct netfs_inode *ctx,
 {
 	struct netfs_io_request *rreq;
 	struct folio *folio;
-	unsigned int fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE;
 	pgoff_t index = pos >> PAGE_SHIFT;
 	int ret;
 
 	DEFINE_READAHEAD(ractl, file, NULL, mapping, index);
 
 retry:
-	folio = __filemap_get_folio(mapping, index, fgp_flags,
+	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
 				    mapping_gfp_mask(mapping));
 	if (!folio)
 		return -ENOMEM;
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 9f1081683771..47069662f4b8 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -507,6 +507,8 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
 #define FGP_ENTRY		0x00000080
 #define FGP_STABLE		0x00000100
 
+#define FGP_WRITEBEGIN		(FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE)
+
 struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 		int fgp_flags, gfp_t gfp);
 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 18c48b557926..668350748828 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -106,9 +106,7 @@ EXPORT_SYMBOL(pagecache_get_page);
 struct page *grab_cache_page_write_begin(struct address_space *mapping,
 					pgoff_t index)
 {
-	unsigned fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE;
-
-	return pagecache_get_page(mapping, index, fgp_flags,
+	return pagecache_get_page(mapping, index, FGP_WRITEBEGIN,
 			mapping_gfp_mask(mapping));
 }
 EXPORT_SYMBOL(grab_cache_page_write_begin);
-- 
2.35.1