linux-kernel - [PATCH v2 2/2] dax: use PG_PMD

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Date:   Tue, 22 Aug 2017 16:24:36 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        "Slusarz, Marcin" <marcin.slusarz@...el.com>
Subject: [PATCH v2 2/2] dax: use PG_PMD_COLOUR instead of open coding

Use ~PG_PMD_COLOUR in dax_entry_waitqueue() instead of open coding an
equivalent page offset mask.

Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 fs/dax.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 865d42c..0e2a1fd 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -42,6 +42,9 @@
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 
+/* The 'colour' (ie low bits) within a PMD of a page offset.  */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
@@ -98,7 +101,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * the range covered by the PMD map to the same bit lock.
 	 */
 	if (dax_is_pmd_entry(entry))
-		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+		index &= ~PG_PMD_COLOUR;
 
 	key->mapping = mapping;
 	key->entry_start = index;
@@ -1262,12 +1265,6 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
 }
 
 #ifdef CONFIG_FS_DAX_PMD
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below functions.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
 static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
 		loff_t pos, void **entryp)
 {
-- 
2.9.5