writeback: fix WB_SYNC_NONE writeback from umount

[net-next-2.6.git] / fs / fs-writeback.c

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 760dc8d0b4ff0863326b5afcb0ba10dc19da13b9..67db89786e7dae77cfdb3bbbc9092e7892393354 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -45,6 +45,7 @@ struct wb_writeback_args {
        int for_kupdate:1;
        int range_cyclic:1;
        int for_background:1;
+       int sb_pinned:1;
 };
 
 /*
@@ -230,6 +231,11 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi,
                .sync_mode      = WB_SYNC_ALL,
                .nr_pages       = LONG_MAX,
                .range_cyclic   = 0,
+               /*
+                * Setting sb_pinned is not necessary for WB_SYNC_ALL, but
+                * lets make it explicitly clear.
+                */
+               .sb_pinned      = 1,
        };
        struct bdi_work work;
 
@@ -245,21 +251,23 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi,
  * @bdi: the backing device to write from
  * @sb: write inodes from this super_block
  * @nr_pages: the number of pages to write
+ * @sb_locked: caller already holds sb umount sem.
  *
  * Description:
  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
  *   started when this function returns, we make no guarentees on
- *   completion. Caller need not hold sb s_umount semaphore.
+ *   completion. Caller specifies whether sb umount sem is held already or not.
  *
  */
 void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
-                        long nr_pages)
+                        long nr_pages, int sb_locked)
 {
        struct wb_writeback_args args = {
                .sb             = sb,
                .sync_mode      = WB_SYNC_NONE,
                .nr_pages       = nr_pages,
                .range_cyclic   = 1,
+               .sb_pinned      = sb_locked,
        };
 
        /*
@@ -577,7 +585,7 @@ static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
        /*
         * Caller must already hold the ref for this
         */
-       if (wbc->sync_mode == WB_SYNC_ALL) {
+       if (wbc->sync_mode == WB_SYNC_ALL || wbc->sb_pinned) {
                WARN_ON(!rwsem_is_locked(&sb->s_umount));
                return SB_NOT_PINNED;
        }
@@ -751,6 +759,7 @@ static long wb_writeback(struct bdi_writeback *wb,
                .for_kupdate            = args->for_kupdate,
                .for_background         = args->for_background,
                .range_cyclic           = args->range_cyclic,
+               .sb_pinned              = args->sb_pinned,
        };
        unsigned long oldest_jif;
        long wrote = 0;
@@ -1193,6 +1202,18 @@ static void wait_sb_inodes(struct super_block *sb)
        iput(old_inode);
 }
 
+static void __writeback_inodes_sb(struct super_block *sb, int sb_locked)
+{
+       unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
+       unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
+       long nr_to_write;
+
+       nr_to_write = nr_dirty + nr_unstable +
+                       (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+
+       bdi_start_writeback(sb->s_bdi, sb, nr_to_write, sb_locked);
+}
+
 /**
  * writeback_inodes_sb -       writeback dirty inodes from given super_block
  * @sb: the superblock
@@ -1204,17 +1225,22 @@ static void wait_sb_inodes(struct super_block *sb)
  */
 void writeback_inodes_sb(struct super_block *sb)
 {
-       unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
-       unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-       long nr_to_write;
-
-       nr_to_write = nr_dirty + nr_unstable +
-                       (inodes_stat.nr_inodes - inodes_stat.nr_unused);
-
-       bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
+       __writeback_inodes_sb(sb, 0);
 }
 EXPORT_SYMBOL(writeback_inodes_sb);
 
+/**
+ * writeback_inodes_sb_locked  - writeback dirty inodes from given super_block
+ * @sb: the superblock
+ *
+ * Like writeback_inodes_sb(), except the caller already holds the
+ * sb umount sem.
+ */
+void writeback_inodes_sb_locked(struct super_block *sb)
+{
+       __writeback_inodes_sb(sb, 1);
+}
+
 /**
  * writeback_inodes_sb_if_idle -       start writeback if none underway
  * @sb: the superblock