linux-next: manual merge of the block tree with the ext4 tree

[Stephen Rothwell]

Hi Jens,

Today's linux-next merge of the block tree got a conflict in
fs/fs-writeback.c between commit ef7fdf5e8c87 ("vfs: add support for a
lazytime mount option") from the ext4 tree and commit 9c6ac78eb352
("writeback: fix a subtle race condition in I_DIRTY clearing") from the
block tree.

I fixed it up (I took a guess, plese check - see below) and can carry
the fix as necessary (no action is required).

-- 
Cheers,
Stephen Rothwell                    s...@canb.auug.org.au

diff --cc fs/fs-writeback.c
index 3d87174408ae,2d609a5fbfea..000000000000
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@@ -482,14 -479,30 +482,30 @@@ __writeback_single_inode(struct inode *
         * write_inode()
         */
        spin_lock(&inode->i_lock);
-       /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
-       if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
-               inode->i_state &= ~I_DIRTY_PAGES;
+ 
 -      dirty = inode->i_state & I_DIRTY;
 -      inode->i_state &= ~I_DIRTY;
 +      dirty = inode->i_state & I_DIRTY_INODE;
 +      inode->i_state &= ~I_DIRTY_INODE;
+ 
+       /*
+        * Paired with smp_mb() in __mark_inode_dirty().  This allows
+        * __mark_inode_dirty() to test i_state without grabbing i_lock -
+        * either they see the I_DIRTY bits cleared or we see the dirtied
+        * inode.
+        *
+        * I_DIRTY_PAGES is always cleared together above even if @mapping
+        * still has dirty pages.  The flag is reinstated after smp_mb() if
+        * necessary.  This guarantees that either __mark_inode_dirty()
+        * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
+        */
+       smp_mb();
+ 
+       if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+               inode->i_state |= I_DIRTY_PAGES;
+ 
        spin_unlock(&inode->i_lock);
+ 
        /* Don't write the inode if only I_DIRTY_PAGES was set */
 -      if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
 +      if (dirty) {
                int err = write_inode(inode, wbc);
                if (ret == 0)
                        ret = err;

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