mm: remove generic_writepages

Now that all external callers are gone, just fold it into do_writepages.

Link: https://lkml.kernel.org/r/20221229161031.391878-7-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/writeback.h

@@ -369,8 +369,6 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb);
 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
 				void *data);
 
-int generic_writepages(struct address_space *mapping,
-		       struct writeback_control *wbc);
 void tag_pages_for_writeback(struct address_space *mapping,
 			     pgoff_t start, pgoff_t end);
 int write_cache_pages(struct address_space *mapping,

mm/page-writeback.c

@@ -2526,12 +2526,8 @@ int write_cache_pages(struct address_space *mapping,
 }
 EXPORT_SYMBOL(write_cache_pages);
 
-/*
- * Function used by generic_writepages to call the real writepage
- * function and set the mapping flags on error
- */
-static int __writepage(struct page *page, struct writeback_control *wbc,
-		       void *data)
+static int writepage_cb(struct page *page, struct writeback_control *wbc,
+		void *data)
 {
 	struct address_space *mapping = data;
 	int ret = mapping->a_ops->writepage(page, wbc);
@@ -2539,34 +2535,6 @@ static int __writepage(struct page *page, struct writeback_control *wbc,
 	return ret;
 }
 
-/**
- * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
- * @mapping: address space structure to write
- * @wbc: subtract the number of written pages from *@wbc->nr_to_write
- *
- * This is a library function, which implements the writepages()
- * address_space_operation.
- *
- * Return: %0 on success, negative error code otherwise
- */
-int generic_writepages(struct address_space *mapping,
-		       struct writeback_control *wbc)
-{
-	struct blk_plug plug;
-	int ret;
-
-	/* deal with chardevs and other special file */
-	if (!mapping->a_ops->writepage)
-		return 0;
-
-	blk_start_plug(&plug);
-	ret = write_cache_pages(mapping, wbc, __writepage, mapping);
-	blk_finish_plug(&plug);
-	return ret;
-}
-
-EXPORT_SYMBOL(generic_writepages);
-
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
 	int ret;
@@ -2577,11 +2545,20 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 	wb = inode_to_wb_wbc(mapping->host, wbc);
 	wb_bandwidth_estimate_start(wb);
 	while (1) {
-		if (mapping->a_ops->writepages)
+		if (mapping->a_ops->writepages) {
 			ret = mapping->a_ops->writepages(mapping, wbc);
-		else
-			ret = generic_writepages(mapping, wbc);
-		if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL))
+		} else if (mapping->a_ops->writepage) {
+			struct blk_plug plug;
+
+			blk_start_plug(&plug);
+			ret = write_cache_pages(mapping, wbc, writepage_cb,
+						mapping);
+			blk_finish_plug(&plug);
+		} else {
+			/* deal with chardevs and other special files */
+			ret = 0;
+		}
+		if (ret != -ENOMEM || wbc->sync_mode != WB_SYNC_ALL)
 			break;
 
 		/*