Patch "Btrfs: igrab inode in writepage" has been added to the 3.10-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Btrfs: igrab inode in writepage

to the 3.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     btrfs-igrab-inode-in-writepage.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From be7bd730841e69fe8f70120098596f648cd1f3ff Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik@fb.com>
Date: Thu, 22 Oct 2015 15:05:09 -0400
Subject: Btrfs: igrab inode in writepage

From: Josef Bacik <jbacik@fb.com>

commit be7bd730841e69fe8f70120098596f648cd1f3ff upstream.

We hit this panic on a few of our boxes this week where we have an
ordered_extent with an NULL inode.  We do an igrab() of the inode in writepages,
but weren't doing it in writepage which can be called directly from the VM on
dirty pages.  If the inode has been unlinked then we could have I_FREEING set
which means igrab() would return NULL and we get this panic.  Fix this by trying
to igrab in btrfs_writepage, and if it returns NULL then just redirty the page
and return AOP_WRITEPAGE_ACTIVATE; so the VM knows it wasn't successful.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/inode.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7477,15 +7477,28 @@ int btrfs_readpage(struct file *file, st
 static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct extent_io_tree *tree;
-
+	struct inode *inode = page->mapping->host;
+	int ret;
 
 	if (current->flags & PF_MEMALLOC) {
 		redirty_page_for_writepage(wbc, page);
 		unlock_page(page);
 		return 0;
 	}
+
+	/*
+	 * If we are under memory pressure we will call this directly from the
+	 * VM, we need to make sure we have the inode referenced for the ordered
+	 * extent.  If not just return like we didn't do anything.
+	 */
+	if (!igrab(inode)) {
+		redirty_page_for_writepage(wbc, page);
+		return AOP_WRITEPAGE_ACTIVATE;
+	}
 	tree = &BTRFS_I(page->mapping->host)->io_tree;
-	return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
+	ret = extent_write_full_page(tree, page, btrfs_get_extent, wbc);
+	btrfs_add_delayed_iput(inode);
+	return ret;
 }
 
 static int btrfs_writepages(struct address_space *mapping,


Patches currently in stable-queue which might be from jbacik@fb.com are

queue-3.10/btrfs-igrab-inode-in-writepage.patch