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-rw-r--r--fs/dax.c34
1 files changed, 34 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 8f70e3b59b91..c576f6181dc8 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -54,6 +54,40 @@ static int __init init_dax_wait_table(void)
}
fs_initcall(init_dax_wait_table);
+/*
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a zero page or
+ * an empty entry that is just used for locking. In total four special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
+ * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
+ */
+#define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
+#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
+
+static unsigned long dax_radix_sector(void *entry)
+{
+ return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+ return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+ ((unsigned long)sector << RADIX_DAX_SHIFT) |
+ RADIX_DAX_ENTRY_LOCK);
+}
+
+static unsigned int dax_radix_order(void *entry)
+{
+ if ((unsigned long)entry & RADIX_DAX_PMD)
+ return PMD_SHIFT - PAGE_SHIFT;
+ return 0;
+}
+
static int dax_is_pmd_entry(void *entry)
{
return (unsigned long)entry & RADIX_DAX_PMD;