writeback: don't call mapping_set_error on AOP_WRITEPAGE_ACTIVATE

Patch series "convert write_cache_pages() to an iterator", v8.

This is an evolution of the series Matthew Wilcox originally sent in June
2023, which has changed quite a bit since and now has a while based
iterator.

This patch (of 14):

mapping_set_error should only be called on 0 returns (which it ignores) or
a negative error code.

writepage_cb ends up being able to call writepage_cb on the magic
AOP_WRITEPAGE_ACTIVATE return value from ->writepage which means success
but the caller needs to unlock the page.  Ignore that and just call
mapping_set_error on negative errors.

(no fixes tag as this goes back more than 20 years over various renames
and refactors so I've given up chasing down the original introduction)

Link: https://lkml.kernel.org/r/20240215063649.2164017-1-hch@lst.de
Link: https://lkml.kernel.org/r/20240215063649.2164017-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 3f255534986a2fda07e2d35187bb385f64749c5c..703e83c69ffe0820fc327619539c7219cf797c13 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2535,7 +2535,9 @@ static int writepage_cb(struct folio *folio, struct writeback_control *wbc,
 {
        struct address_space *mapping = data;
        int ret = mapping->a_ops->writepage(&folio->page, wbc);
-       mapping_set_error(mapping, ret);
+
+       if (ret < 0)
+               mapping_set_error(mapping, ret);
        return ret;
 }