Merge tag 'xarray-5.5' of git://git.infradead.org/users/willy/linux-dax

Pull XArray fixes from Matthew Wilcox:
 "Primarily bugfixes, mostly around handling index wrap-around
  correctly.

  A couple of doc fixes and adding missing APIs.

  I had an oops live on stage at linux.conf.au this year, and it turned
  out to be a bug in xas_find() which I can't prove isn't triggerable in
  the current codebase. Then in looking for the bug, I spotted two more
  bugs.

  The bots have had a few days to chew on this with no problems
  reported, and it passes the test-suite (which now has more tests to
  make sure these problems don't come back)"

* tag 'xarray-5.5' of git://git.infradead.org/users/willy/linux-dax:
  XArray: Add xa_for_each_range
  XArray: Fix xas_find returning too many entries
  XArray: Fix xa_find_after with multi-index entries
  XArray: Fix infinite loop with entry at ULONG_MAX
  XArray: Add wrappers for nested spinlocks
  XArray: Improve documentation of search marks
  XArray: Fix xas_pause at ULONG_MAX

1 files changed, 40 insertions, 5 deletions

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 86eecbd98e84..f73e1775ded0 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -417,6 +417,36 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
 }
 
 /**
+ * xa_for_each_range() - Iterate over a portion of an XArray.
+ * @xa: XArray.
+ * @index: Index of @entry.
+ * @entry: Entry retrieved from array.
+ * @start: First index to retrieve from array.
+ * @last: Last index to retrieve from array.
+ *
+ * During the iteration, @entry will have the value of the entry stored
+ * in @xa at @index.  You may modify @index during the iteration if you
+ * want to skip or reprocess indices.  It is safe to modify the array
+ * during the iteration.  At the end of the iteration, @entry will be set
+ * to NULL and @index will have a value less than or equal to max.
+ *
+ * xa_for_each_range() is O(n.log(n)) while xas_for_each() is O(n).  You have
+ * to handle your own locking with xas_for_each(), and if you have to unlock
+ * after each iteration, it will also end up being O(n.log(n)).
+ * xa_for_each_range() will spin if it hits a retry entry; if you intend to
+ * see retry entries, you should use the xas_for_each() iterator instead.
+ * The xas_for_each() iterator will expand into more inline code than
+ * xa_for_each_range().
+ *
+ * Context: Any context.  Takes and releases the RCU lock.
+ */
+#define xa_for_each_range(xa, index, entry, start, last)		\
+	for (index = start,						\
+	     entry = xa_find(xa, &index, last, XA_PRESENT);		\
+	     entry;							\
+	     entry = xa_find_after(xa, &index, last, XA_PRESENT))
+
+/**
  * xa_for_each_start() - Iterate over a portion of an XArray.
  * @xa: XArray.
  * @index: Index of @entry.
@@ -439,11 +469,8 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
  *
  * Context: Any context.  Takes and releases the RCU lock.
  */
-#define xa_for_each_start(xa, index, entry, start)			\
-	for (index = start,						\
-	     entry = xa_find(xa, &index, ULONG_MAX, XA_PRESENT);	\
-	     entry;							\
-	     entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT))
+#define xa_for_each_start(xa, index, entry, start) \
+	xa_for_each_range(xa, index, entry, start, ULONG_MAX)
 
 /**
  * xa_for_each() - Iterate over present entries in an XArray.
@@ -508,6 +535,14 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
 				spin_lock_irqsave(&(xa)->xa_lock, flags)
 #define xa_unlock_irqrestore(xa, flags) \
 				spin_unlock_irqrestore(&(xa)->xa_lock, flags)
+#define xa_lock_nested(xa, subclass) \
+				spin_lock_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_bh_nested(xa, subclass) \
+				spin_lock_bh_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_irq_nested(xa, subclass) \
+				spin_lock_irq_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_irqsave_nested(xa, flags, subclass) \
+		spin_lock_irqsave_nested(&(xa)->xa_lock, flags, subclass)
 
 /*
  * Versions of the normal API which require the caller to hold the