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SUNRPC: Fix a potential race in rpc_wake_up_task() 

Use RCU to ensure that we can safely call rpc_finish_wakeup after we've
called __rpc_do_wake_up_task. If not, there is a theoretical race, in which
the rpc_task finishes executing, and gets freed first.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2006-11-13 16:23:44 -05:00
parent e6b3c4db6f
commit 8aca67f0ae
5 changed files with 47 additions and 20 deletions
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8
fs/nfs/read.c
View File

@ -65,13 +65,19 @@ struct nfs_read_data *nfs_readdata_alloc(size_t len)
return p;
}
static void nfs_readdata_free(struct nfs_read_data *p)
static void nfs_readdata_rcu_free(struct rcu_head *head)
{
struct nfs_read_data *p = container_of(head, struct nfs_read_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_rdata_mempool);
}
static void nfs_readdata_free(struct nfs_read_data *rdata)
{
call_rcu_bh(&rdata->task.u.tk_rcu, nfs_readdata_rcu_free);
}
void nfs_readdata_release(void *data)
{
nfs_readdata_free(data);

20
fs/nfs/write.c
View File

@ -102,13 +102,19 @@ struct nfs_write_data *nfs_commit_alloc(void)
return p;
}
void nfs_commit_free(struct nfs_write_data *p)
void nfs_commit_rcu_free(struct rcu_head *head)
{
struct nfs_write_data *p = container_of(head, struct nfs_write_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_commit_mempool);
}
void nfs_commit_free(struct nfs_write_data *wdata)
{
call_rcu_bh(&wdata->task.u.tk_rcu, nfs_commit_rcu_free);
}
struct nfs_write_data *nfs_writedata_alloc(size_t len)
{
unsigned int pagecount = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
@ -131,13 +137,19 @@ struct nfs_write_data *nfs_writedata_alloc(size_t len)
return p;
}
static void nfs_writedata_free(struct nfs_write_data *p)
static void nfs_writedata_rcu_free(struct rcu_head *head)
{
struct nfs_write_data *p = container_of(head, struct nfs_write_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_wdata_mempool);
}
static void nfs_writedata_free(struct nfs_write_data *wdata)
{
call_rcu_bh(&wdata->task.u.tk_rcu, nfs_writedata_rcu_free);
}
void nfs_writedata_release(void *wdata)
{
nfs_writedata_free(wdata);
@ -258,7 +270,7 @@ static int nfs_writepage_sync(struct nfs_open_context *ctx, struct inode *inode,
io_error:
nfs_end_data_update(inode);
end_page_writeback(page);
nfs_writedata_free(wdata);
nfs_writedata_release(wdata);
return written ? written : result;
}
@ -1043,7 +1055,7 @@ out_bad:
while (!list_empty(&list)) {
data = list_entry(list.next, struct nfs_write_data, pages);
list_del(&data->pages);
nfs_writedata_free(data);
nfs_writedata_release(data);
}
nfs_mark_request_dirty(req);
nfs_clear_page_writeback(req);

7
include/linux/nfs_fs.h
View File

@ -428,11 +428,6 @@ extern int nfs_updatepage(struct file *, struct page *, unsigned int, unsigned
extern int nfs_writeback_done(struct rpc_task *, struct nfs_write_data *);
extern void nfs_writedata_release(void *);
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
struct nfs_write_data *nfs_commit_alloc(void);
void nfs_commit_free(struct nfs_write_data *p);
#endif
/*
* Try to write back everything synchronously (but check the
* return value!)
@ -440,6 +435,8 @@ void nfs_commit_free(struct nfs_write_data *p);
extern int nfs_sync_inode_wait(struct inode *, unsigned long, unsigned int, int);
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
extern int nfs_commit_inode(struct inode *, int);
extern struct nfs_write_data *nfs_commit_alloc(void);
extern void nfs_commit_free(struct nfs_write_data *wdata);
extern void nfs_commit_release(void *wdata);
#else
static inline int

2
include/linux/sunrpc/sched.h
View File

@ -11,6 +11,7 @@
#include <linux/timer.h>
#include <linux/sunrpc/types.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
@ -85,6 +86,7 @@ struct rpc_task {
union {
struct work_struct tk_work; /* Async task work queue */
struct rpc_wait tk_wait; /* RPC wait */
struct rcu_head tk_rcu; /* for task deletion */
} u;
unsigned short tk_timeouts; /* maj timeouts */

30
net/sunrpc/sched.c
View File

@ -427,16 +427,19 @@ __rpc_default_timer(struct rpc_task *task)
*/
void rpc_wake_up_task(struct rpc_task *task)
{
rcu_read_lock_bh();
if (rpc_start_wakeup(task)) {
if (RPC_IS_QUEUED(task)) {
struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;
spin_lock_bh(&queue->lock);
/* Note: we're already in a bh-safe context */
spin_lock(&queue->lock);
__rpc_do_wake_up_task(task);
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
}
rpc_finish_wakeup(task);
}
rcu_read_unlock_bh();
}
/*
@ -499,14 +502,16 @@ struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
struct rpc_task *task = NULL;
dprintk("RPC: wake_up_next(%p \"%s\")\n", queue, rpc_qname(queue));
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
if (RPC_IS_PRIORITY(queue))
task = __rpc_wake_up_next_priority(queue);
else {
task_for_first(task, &queue->tasks[0])
__rpc_wake_up_task(task);
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
return task;
}
@ -522,7 +527,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
struct rpc_task *task, *next;
struct list_head *head;
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list)
@ -531,7 +537,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}
/**
@ -546,7 +553,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
struct rpc_task *task, *next;
struct list_head *head;
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
@ -557,7 +565,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}
static void __rpc_atrun(struct rpc_task *task)
@ -817,8 +826,9 @@ rpc_alloc_task(void)
return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
}
static void rpc_free_task(struct rpc_task *task)
static void rpc_free_task(struct rcu_head *rcu)
{
struct rpc_task *task = container_of(rcu, struct rpc_task, u.tk_rcu);
dprintk("RPC: %4d freeing task\n", task->tk_pid);
mempool_free(task, rpc_task_mempool);
}
@ -872,7 +882,7 @@ void rpc_put_task(struct rpc_task *task)
task->tk_client = NULL;
}
if (task->tk_flags & RPC_TASK_DYNAMIC)
rpc_free_task(task);
call_rcu_bh(&task->u.tk_rcu, rpc_free_task);
if (tk_ops->rpc_release)
tk_ops->rpc_release(calldata);
}