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afs: Mark afs_net::ws_cell as __rcu and set using rcu functions 

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: f044c8847b ("afs: Lay the groundwork for supporting network namespaces")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
hifive-unleashed-5.1
David Howells 2018-05-23 11:51:29 +01:00
parent c875c76a06
commit 1588def91d
3 changed files with 6 additions and 6 deletions
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8
fs/afs/cell.c
View File

@ -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);

2
fs/afs/internal.h
View File

@ -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;

2
fs/afs/proc.c
View File

@ -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();