[PATCH 208/222] NFS: Ensure that we free the rpc_task after read and write cleanups are done

[Herton Ronaldo Krzesinski]

3.5.7.3 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <Trond.Myklebust at netapp.com>

commit 6db6dd7d3fd8f7c765dabc376493d6791ab28bd6 upstream.

This patch ensures that we free the rpc_task after the cleanup callbacks
are done in order to avoid a deadlock problem that can be triggered if
the callback needs to wait for another workqueue item to complete.

Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Cc: Weston Andros Adamson <dros at netapp.com>
Cc: Tejun Heo <tj at kernel.org>
Cc: Bruce Fields <bfields at fieldses.org>
[ herton: adjust context ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 fs/nfs/read.c  |   10 +++++++---
 fs/nfs/write.c |   10 +++++++---
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 86ced78..b151ad5 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -91,12 +91,16 @@ void nfs_readdata_release(struct nfs_read_data *rdata)
 	put_nfs_open_context(rdata->args.context);
 	if (rdata->pages.pagevec != rdata->pages.page_array)
 		kfree(rdata->pages.pagevec);
-	if (rdata != &read_header->rpc_data)
-		kfree(rdata);
-	else
+	if (rdata == &read_header->rpc_data) {
 		rdata->header = NULL;
+		rdata = NULL;
+	}
 	if (atomic_dec_and_test(&hdr->refcnt))
 		hdr->completion_ops->completion(hdr);
+	/* Note: we only free the rpc_task after callbacks are done.
+	 * See the comment in rpc_free_task() for why
+	 */
+	kfree(rdata);
 }
 
 static
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index bce88ac..a440deb 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -124,12 +124,16 @@ void nfs_writedata_release(struct nfs_write_data *wdata)
 	put_nfs_open_context(wdata->args.context);
 	if (wdata->pages.pagevec != wdata->pages.page_array)
 		kfree(wdata->pages.pagevec);
-	if (wdata != &write_header->rpc_data)
-		kfree(wdata);
-	else
+	if (wdata == &write_header->rpc_data) {
 		wdata->header = NULL;
+		wdata = NULL;
+	}
 	if (atomic_dec_and_test(&hdr->refcnt))
 		hdr->completion_ops->completion(hdr);
+	/* Note: we only free the rpc_task after callbacks are done.
+	 * See the comment in rpc_free_task() for why
+	 */
+	kfree(wdata);
 }
 
 static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
-- 
1.7.9.5