Merge tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux

Pull writeback fixes from Wu Fengguang:
 "Two writeback fixes

   - fix negative (setpoint - dirty) in 32bit archs

   - use down_read_trylock() in writeback_inodes_sb(_nr)_if_idle()"

* tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
  Negative (setpoint-dirty) in bdi_position_ratio()
  vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename them

1 files changed, 20 insertions, 24 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 359494ea1bde..21f46fb3a101 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1344,47 +1344,43 @@ void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
 EXPORT_SYMBOL(writeback_inodes_sb);
 
 /**
- * writeback_inodes_sb_if_idle  -       start writeback if none underway
+ * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
  * @sb: the superblock
- * @reason: reason why some writeback work was initiated
+ * @nr: the number of pages to write
+ * @reason: the reason of writeback
  *
- * Invoke writeback_inodes_sb if no writeback is currently underway.
+ * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
  * Returns 1 if writeback was started, 0 if not.
  */
-int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
+int try_to_writeback_inodes_sb_nr(struct super_block *sb,
+                                  unsigned long nr,
+                                  enum wb_reason reason)
 {
-        if (!writeback_in_progress(sb->s_bdi)) {
-                down_read(&sb->s_umount);
-                writeback_inodes_sb(sb, reason);
-                up_read(&sb->s_umount);
+        if (writeback_in_progress(sb->s_bdi))
                 return 1;
-        } else
+
+        if (!down_read_trylock(&sb->s_umount))
                 return 0;
+
+        writeback_inodes_sb_nr(sb, nr, reason);
+        up_read(&sb->s_umount);
+        return 1;
 }
-EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
+EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
 
 /**
- * writeback_inodes_sb_nr_if_idle       -       start writeback if none underway
+ * try_to_writeback_inodes_sb - try to start writeback if none underway
  * @sb: the superblock
- * @nr: the number of pages to write
  * @reason: reason why some writeback work was initiated
  *
- * Invoke writeback_inodes_sb if no writeback is currently underway.
+ * Implement by try_to_writeback_inodes_sb_nr()
  * Returns 1 if writeback was started, 0 if not.
  */
-int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
-                                   unsigned long nr,
-                                   enum wb_reason reason)
+int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
 {
-        if (!writeback_in_progress(sb->s_bdi)) {
-                down_read(&sb->s_umount);
-                writeback_inodes_sb_nr(sb, nr, reason);
-                up_read(&sb->s_umount);
-                return 1;
-        } else
-                return 0;
+        return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
 }
-EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
+EXPORT_SYMBOL(try_to_writeback_inodes_sb);
 
 /**
  * sync_inodes_sb       -       sync sb inode pages