XArray: Change xa_insert to return -EBUSY

Userspace translates EEXIST to "File exists" which isn't a very good
error message for the problem.  "Device or resource busy" is a better
indication of what went wrong.
Signed-off-by: Matthew Wilcox <willy@infradead.org>

Documentation/core-api/xarray.rst

@@ -85,7 +85,7 @@ which was at that index; if it returns the same entry which was passed as
 
 If you want to only store a new entry to an index if the current entry
 at that index is ``NULL``, you can use :c:func:`xa_insert` which
-returns ``-EEXIST`` if the entry is not empty.
+returns ``-EBUSY`` if the entry is not empty.
 
 You can enquire whether a mark is set on an entry by using
 :c:func:`xa_get_mark`.  If the entry is not ``NULL``, you can set a mark

fs/nilfs2/btnode.c

@@ -189,7 +189,7 @@ int nilfs_btnode_prepare_change_key(struct address_space *btnc,
 		 */
 		if (!err)
 			return 0;
-		else if (err != -EEXIST)
+		else if (err != -EBUSY)
 			goto failed_unlock;
 
 		err = invalidate_inode_pages2_range(btnc, newkey, newkey);

include/linux/xarray.h

@@ -664,7 +664,7 @@ static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
  *
  * Context: Any context.  Takes and releases the xa_lock.  May sleep if
  * the @gfp flags permit.
- * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
  * -ENOMEM if memory could not be allocated.
  */
 static inline int xa_insert(struct xarray *xa, unsigned long index,
@@ -693,7 +693,7 @@ static inline int xa_insert(struct xarray *xa, unsigned long index,
  *
  * Context: Any context.  Takes and releases the xa_lock while
  * disabling softirqs.  May sleep if the @gfp flags permit.
- * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
  * -ENOMEM if memory could not be allocated.
  */
 static inline int xa_insert_bh(struct xarray *xa, unsigned long index,
@@ -722,7 +722,7 @@ static inline int xa_insert_bh(struct xarray *xa, unsigned long index,
  *
  * Context: Process context.  Takes and releases the xa_lock while
  * disabling interrupts.  May sleep if the @gfp flags permit.
- * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
  * -ENOMEM if memory could not be allocated.
  */
 static inline int xa_insert_irq(struct xarray *xa, unsigned long index,

lib/test_xarray.c

@@ -346,7 +346,7 @@ static noinline void check_cmpxchg(struct xarray *xa)
 
 	XA_BUG_ON(xa, !xa_empty(xa));
 	XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_KERNEL) != NULL);
-	XA_BUG_ON(xa, xa_insert(xa, 12345678, xa, GFP_KERNEL) != -EEXIST);
+	XA_BUG_ON(xa, xa_insert(xa, 12345678, xa, GFP_KERNEL) != -EBUSY);
 	XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, SIX, FIVE, GFP_KERNEL) != LOTS);
 	XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, LOTS, FIVE, GFP_KERNEL) != LOTS);
 	XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, FIVE, LOTS, GFP_KERNEL) != FIVE);
@@ -388,7 +388,7 @@ static noinline void check_reserve(struct xarray *xa)
 	/* But xa_insert does not */
 	xa_reserve(xa, 12345678, GFP_KERNEL);
 	XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) !=
-			-EEXIST);
+			-EBUSY);
 	XA_BUG_ON(xa, xa_empty(xa));
 	XA_BUG_ON(xa, xa_erase(xa, 12345678) != NULL);
 	XA_BUG_ON(xa, !xa_empty(xa));

lib/xarray.c

@@ -1451,7 +1451,7 @@ EXPORT_SYMBOL(__xa_cmpxchg);
  *
  * Context: Any context.  Expects xa_lock to be held on entry.  May
  * release and reacquire xa_lock if @gfp flags permit.
- * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
  * -ENOMEM if memory could not be allocated.
  */
 int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
@@ -1471,7 +1471,7 @@ int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
 			if (xa_track_free(xa))
 				xas_clear_mark(&xas, XA_FREE_MARK);
 		} else {
-			xas_set_err(&xas, -EEXIST);
+			xas_set_err(&xas, -EBUSY);
 		}
 	} while (__xas_nomem(&xas, gfp));