linux-kernel - [PATCH v2 3/4] mm/truncate: bail out early from invalidate_inode_pages2

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Date:   Mon, 24 Apr 2017 19:41:34 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>
CC:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>,
        Alexey Kuznetsov <kuznet@...tuozzo.com>,
        Christoph Hellwig <hch@....de>,
        Nikolay Borisov <n.borisov.lkml@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-mm@...ck.org>
Subject: [PATCH v2 3/4] mm/truncate: bail out early from invalidate_inode_pages2_range() if mapping is empty

If mapping is empty (both ->nrpages and ->nrexceptional is zero) we can
avoid pointless lookups in empty radix tree and bail out immediately after
cleancache invalidation.

Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 mm/truncate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/truncate.c b/mm/truncate.c
index 6263aff..8f12b0e 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -624,6 +624,9 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	int did_range_unmap = 0;
 
 	cleancache_invalidate_inode(mapping);
+	if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
+		return 0;
+
 	pagevec_init(&pvec, 0);
 	index = start;
 	while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
-- 
2.10.2