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

Stephen Rothwell
2014-11-26T02:42:14Z

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Hi Jens,

Today's linux-next merge of the block tree got a conflict in
fs/fs-writeback.c between commit 74ba19abbeae ("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 (maybe, please check - see below) and can carry the fix
as necessary (no action is required).

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

diff --cc fs/fs-writeback.c
index cab2d6d74828,2d609a5fbfea..000000000000
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@@ -480,12 -479,28 +480,28 @@@ __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_SYNC | I_DIRTY_DATASYNC | I_DIRTY_TIME);
- inode->i_state &= ~I_DIRTY;
++ inode->i_state &= ~(I_DIRTY | I_DIRTY_TIME);
+
+ /*
+ * 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)) {
int err = write_inode(inode, wbc);

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