Obsolete scoutfs_writepage

Due to folios, the kernel will call scoutfs_writepages() and this
becomes unused. It could be ported but the helper function to call isn't
exported anymore.

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/Makefile.kernelcompat

@@ -306,6 +306,17 @@ ifneq (,$(shell grep 'int buffer_migrate_folio.struct address_space' include/lin
 ccflags-y += -DKC_HAVE_BUFFER_MIGRATE_FOLIO
 endif
 
+#
+# v6.7-rc4-307-g17bf23a981be
+#
+# block_write_full_page() is replaced with block_write_full_folio(),
+# but that isn't exported as it used to be (and the only users now
+# are builtin). However, the kernel will fall back to using the
+# .writepages method instead, so we can drop this method.
+ifneq (,$(shell grep 'int block_write_full_page.struct page' include/linux/buffer_head.h))
+ccflags-y += -DKC_HAVE_BLOCK_WRITE_FULL_PAGE
+endif
+
 #
 # v6.15-13744-g41cb08555c41
 #

kmod/src/data.c

@@ -785,10 +785,12 @@ static void scoutfs_readahead(struct readahead_control *rac)
 	scoutfs_unlock(sb, inode_lock, SCOUTFS_LOCK_READ);
 }
 
+#ifdef KC_HAVE_BLOCK_WRITE_FULL_PAGE
 static int scoutfs_writepage(struct page *page, struct writeback_control *wbc)
 {
 	return block_write_full_page(page, scoutfs_get_block_write, wbc);
 }
+#endif
 
 static int scoutfs_writepages(struct address_space *mapping,
 			      struct writeback_control *wbc)
@@ -2246,7 +2248,9 @@ const struct address_space_operations scoutfs_file_aops = {
 	.readpage		= scoutfs_readpage,
 #endif
 	.readahead		= scoutfs_readahead,
+#ifdef KC_HAVE_BLOCK_WRITE_FULL_PAGE
 	.writepage		= scoutfs_writepage,
+#endif
 	.writepages		= scoutfs_writepages,
 	.write_begin		= scoutfs_write_begin,
 	.write_end		= scoutfs_write_end,