linux-kernel - [PATCH 2/2] mm/filemap: rewrite mapping_needs

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Date:   Mon, 22 Jul 2019 12:36:10 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>
Subject: [PATCH 2/2] mm/filemap: rewrite mapping_needs_writeback in less
 fancy manner

This actually checks that writeback is needed or in progress.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 mm/filemap.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index d9572593e5c7..29f503ffd70b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -618,10 +618,13 @@ int filemap_fdatawait_keep_errors(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
 
+/* Returns true if writeback might be needed or already in progress. */
 static bool mapping_needs_writeback(struct address_space *mapping)
 {
-	return (!dax_mapping(mapping) && mapping->nrpages) ||
-	    (dax_mapping(mapping) && mapping->nrexceptional);
+	if (dax_mapping(mapping))
+		return mapping->nrexceptional;
+
+	return mapping->nrpages;
 }
 
 int filemap_write_and_wait(struct address_space *mapping)