1 files changed, 105 insertions, 69 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 49bc1b8e8f19..4b37f7cea4dd 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
+#include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
@@ -242,6 +243,7 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi,
 /**
  * bdi_start_writeback - start writeback
  * @bdi: the backing device to write from
+ * @sb: write inodes from this super_block
  * @nr_pages: the number of pages to write
  *
  * Description:
@@ -380,10 +382,10 @@ static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
         move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
 }
 
-static int write_inode(struct inode *inode, int sync)
+static int write_inode(struct inode *inode, struct writeback_control *wbc)
 {
         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
-                return inode->i_sb->s_op->write_inode(inode, sync);
+                return inode->i_sb->s_op->write_inode(inode, wbc);
         return 0;
 }
 
@@ -420,7 +422,6 @@ static int
 writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 {
         struct address_space *mapping = inode->i_mapping;
-        int wait = wbc->sync_mode == WB_SYNC_ALL;
         unsigned dirty;
         int ret;
 
@@ -438,7 +439,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
                  * We'll have another go at writing back this inode when we
                  * completed a full scan of b_io.
                  */
-                if (!wait) {
+                if (wbc->sync_mode != WB_SYNC_ALL) {
                         requeue_io(inode);
                         return 0;
                 }
@@ -460,15 +461,20 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 
         ret = do_writepages(mapping, wbc);
 
-        /* Don't write the inode if only I_DIRTY_PAGES was set */
-        if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
-                int err = write_inode(inode, wait);
+        /*
+         * Make sure to wait on the data before writing out the metadata.
+         * This is important for filesystems that modify metadata on data
+         * I/O completion.
+         */
+        if (wbc->sync_mode == WB_SYNC_ALL) {
+                int err = filemap_fdatawait(mapping);
                 if (ret == 0)
                         ret = err;
         }
 
-        if (wait) {
-                int err = filemap_fdatawait(mapping);
+        /* Don't write the inode if only I_DIRTY_PAGES was set */
+        if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
+                int err = write_inode(inode, wbc);
                 if (ret == 0)
                         ret = err;
         }
@@ -548,108 +554,85 @@ select_queue:
         return ret;
 }
 
-static void unpin_sb_for_writeback(struct super_block **psb)
+static void unpin_sb_for_writeback(struct super_block *sb)
 {
-        struct super_block *sb = *psb;
-
-        if (sb) {
-                up_read(&sb->s_umount);
-                put_super(sb);
-                *psb = NULL;
-        }
+        up_read(&sb->s_umount);
+        put_super(sb);
 }
 
+enum sb_pin_state {
+        SB_PINNED,
+        SB_NOT_PINNED,
+        SB_PIN_FAILED
+};
+
 /*
  * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
  * before calling writeback. So make sure that we do pin it, so it doesn't
  * go away while we are writing inodes from it.
- *
- * Returns 0 if the super was successfully pinned (or pinning wasn't needed),
- * 1 if we failed.
  */
-static int pin_sb_for_writeback(struct writeback_control *wbc,
-                                struct inode *inode, struct super_block **psb)
+static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
+                                              struct super_block *sb)
 {
-        struct super_block *sb = inode->i_sb;
-
-        /*
-         * If this sb is already pinned, nothing more to do. If not and
-         * *psb is non-NULL, unpin the old one first
-         */
-        if (sb == *psb)
-                return 0;
-        else if (*psb)
-                unpin_sb_for_writeback(psb);
-
         /*
          * Caller must already hold the ref for this
          */
         if (wbc->sync_mode == WB_SYNC_ALL) {
                 WARN_ON(!rwsem_is_locked(&sb->s_umount));
-                return 0;
+                return SB_NOT_PINNED;
         }
-
         spin_lock(&sb_lock);
         sb->s_count++;
         if (down_read_trylock(&sb->s_umount)) {
                 if (sb->s_root) {
                         spin_unlock(&sb_lock);
-                        goto pinned;
+                        return SB_PINNED;
                 }
                 /*
                  * umounted, drop rwsem again and fall through to failure
                  */
                 up_read(&sb->s_umount);
         }
-
         sb->s_count--;
         spin_unlock(&sb_lock);
-        return 1;
-pinned:
-        *psb = sb;
-        return 0;
+        return SB_PIN_FAILED;
 }
 
-static void writeback_inodes_wb(struct bdi_writeback *wb,
-                                struct writeback_control *wbc)
+/*
+ * Write a portion of b_io inodes which belong to @sb.
+ * If @wbc->sb != NULL, then find and write all such
+ * inodes. Otherwise write only ones which go sequentially
+ * in reverse order.
+ * Return 1, if the caller writeback routine should be
+ * interrupted. Otherwise return 0.
+ */
+static int writeback_sb_inodes(struct super_block *sb,
+                               struct bdi_writeback *wb,
+                               struct writeback_control *wbc)
 {
-        struct super_block *sb = wbc->sb, *pin_sb = NULL;
-        const unsigned long start = jiffies;    /* livelock avoidance */
-
-        spin_lock(&inode_lock);
-
-        if (!wbc->for_kupdate || list_empty(&wb->b_io))
-                queue_io(wb, wbc->older_than_this);
-
         while (!list_empty(&wb->b_io)) {
-                struct inode *inode = list_entry(wb->b_io.prev,
-                                                struct inode, i_list);
                 long pages_skipped;
-
-                /*
-                 * super block given and doesn't match, skip this inode
-                 */
-                if (sb && sb != inode->i_sb) {
+                struct inode *inode = list_entry(wb->b_io.prev,
+                                                 struct inode, i_list);
+                if (wbc->sb && sb != inode->i_sb) {
+                        /* super block given and doesn't
+                           match, skip this inode */
                         redirty_tail(inode);
                         continue;
                 }
-
+                if (sb != inode->i_sb)
+                        /* finish with this superblock */
+                        return 0;
                 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
                         requeue_io(inode);
                         continue;
                 }
-
                 /*
                  * Was this inode dirtied after sync_sb_inodes was called?
                  * This keeps sync from extra jobs and livelock.
                  */
-                if (inode_dirtied_after(inode, start))
-                        break;
-
-                if (pin_sb_for_writeback(wbc, inode, &pin_sb)) {
-                        requeue_io(inode);
-                        continue;
-                }
+                if (inode_dirtied_after(inode, wbc->wb_start))
+                        return 1;
 
                 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
                 __iget(inode);
@@ -668,14 +651,50 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
                 spin_lock(&inode_lock);
                 if (wbc->nr_to_write <= 0) {
                         wbc->more_io = 1;
-                        break;
+                        return 1;
                 }
                 if (!list_empty(&wb->b_more_io))
                         wbc->more_io = 1;
         }
+        /* b_io is empty */
+        return 1;
+}
+
+static void writeback_inodes_wb(struct bdi_writeback *wb,
+                                struct writeback_control *wbc)
+{
+        int ret = 0;
 
-        unpin_sb_for_writeback(&pin_sb);
+        wbc->wb_start = jiffies; /* livelock avoidance */
+        spin_lock(&inode_lock);
+        if (!wbc->for_kupdate || list_empty(&wb->b_io))
+                queue_io(wb, wbc->older_than_this);
 
+        while (!list_empty(&wb->b_io)) {
+                struct inode *inode = list_entry(wb->b_io.prev,
+                                                 struct inode, i_list);
+                struct super_block *sb = inode->i_sb;
+                enum sb_pin_state state;
+
+                if (wbc->sb && sb != wbc->sb) {
+                        /* super block given and doesn't
+                           match, skip this inode */
+                        redirty_tail(inode);
+                        continue;
+                }
+                state = pin_sb_for_writeback(wbc, sb);
+
+                if (state == SB_PIN_FAILED) {
+                        requeue_io(inode);
+                        continue;
+                }
+                ret = writeback_sb_inodes(sb, wb, wbc);
+
+                if (state == SB_PINNED)
+                        unpin_sb_for_writeback(sb);
+                if (ret)
+                        break;
+        }
         spin_unlock(&inode_lock);
         /* Leave any unwritten inodes on b_io */
 }
@@ -1187,6 +1206,23 @@ void writeback_inodes_sb(struct super_block *sb)
 EXPORT_SYMBOL(writeback_inodes_sb);
 
 /**
+ * writeback_inodes_sb_if_idle  -       start writeback if none underway
+ * @sb: the superblock
+ *
+ * Invoke writeback_inodes_sb 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)
+{
+        if (!writeback_in_progress(sb->s_bdi)) {
+                writeback_inodes_sb(sb);
+                return 1;
+        } else
+                return 0;
+}
+EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
+
+/**
  * sync_inodes_sb       -       sync sb inode pages
  * @sb: the superblock
  *