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From: David Howells <dhowells@redhat.com>
To: viro@zeniv.linux.org.uk
Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org,
	linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 7/8] afs: Mark afs_net::ws_cell as __rcu and set using rcu functions
Date: Wed, 23 May 2018 13:17:25 +0100	[thread overview]
Message-ID: <152707784586.27887.18287659934370022329.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <152707780120.27887.10118775145086304138.stgit@warthog.procyon.org.uk>

The afs_net::ws_cell member is sometimes used under RCU conditions from
within an seq-readlock.  It isn't, however, marked __rcu and it isn't set
using the proper RCU barrier-imposing functions.

Fix this by annotating it with __rcu and using appropriate barriers to
make sure accesses are correctly ordered.

Without this, the code can produce the following warning:

>> fs/afs/proc.c:151:24: sparse: incompatible types in comparison expression (different address spaces)

Fixes: f044c8847bb6 ("afs: Lay the groundwork for supporting network namespaces")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/cell.c     |    8 ++++----
 fs/afs/internal.h |    2 +-
 fs/afs/proc.c     |    2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index fdf4c36cff79..80fd127239ce 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -341,8 +341,8 @@ int afs_cell_init(struct afs_net *net, const char *rootcell)
 
 	/* install the new cell */
 	write_seqlock(&net->cells_lock);
-	old_root = net->ws_cell;
-	net->ws_cell = new_root;
+	old_root = rcu_access_pointer(net->ws_cell);
+	rcu_assign_pointer(net->ws_cell, new_root);
 	write_sequnlock(&net->cells_lock);
 
 	afs_put_cell(net, old_root);
@@ -755,8 +755,8 @@ void afs_cell_purge(struct afs_net *net)
 	_enter("");
 
 	write_seqlock(&net->cells_lock);
-	ws = net->ws_cell;
-	net->ws_cell = NULL;
+	ws = rcu_access_pointer(net->ws_cell);
+	RCU_INIT_POINTER(net->ws_cell, NULL);
 	write_sequnlock(&net->cells_lock);
 	afs_put_cell(net, ws);
 
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index f8086ec95e24..5d922ad148a8 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -231,7 +231,7 @@ struct afs_net {
 
 	/* Cell database */
 	struct rb_root		cells;
-	struct afs_cell		*ws_cell;
+	struct afs_cell __rcu	*ws_cell;
 	struct work_struct	cells_manager;
 	struct timer_list	cells_timer;
 	atomic_t		cells_outstanding;
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index b45ee7576aa8..362f281b1b16 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -173,7 +173,7 @@ static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,
 
 	if (*_pos > 0)
 		return 0;
-	if (!net->ws_cell)
+	if (!rcu_access_pointer(net->ws_cell))
 		return 0;
 
 	rcu_read_lock();

  parent reply	other threads:[~2018-05-23 12:17 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-23 12:16 [PATCH 0/8] afs: Network-namespacing David Howells
2018-05-23 12:16 ` [PATCH 1/8] afs: Move /proc management functions to the end of the file David Howells
2018-05-23 12:16 ` [PATCH 2/8] afs: Rearrange fs/afs/proc.c by moving fops and open functions down David Howells
2018-05-23 12:17 ` [PATCH 3/8] afs: Rearrange fs/afs/proc.c to move the show routines up David Howells
2018-05-23 12:17 ` [PATCH 4/8] afs: Rearrange fs/afs/proc.c to remove remaining predeclarations David Howells
2018-05-23 12:17 ` [PATCH 5/8] proc: Add a way to make network proc files writable David Howells
2018-05-23 12:17 ` [PATCH 6/8] afs: Fix a Sparse warning in xdr_decode_AFSFetchStatus() David Howells
2018-05-23 12:17 ` David Howells [this message]
2018-05-23 12:17 ` [PATCH 8/8] afs: Implement network namespacing David Howells

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