linux/fs/lockd/clntlock.c
Trond Myklebust 28df955a2a NLM: Fix reclaim races
Currently it is possible for a task to remove its locks at the same time as
the NLM recovery thread is trying to recover them. This quickly leads to an
Oops.
Protect the locks using an rw semaphore while they are being recovered.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2006-06-09 09:40:27 -04:00

240 lines
5.8 KiB
C

/*
* linux/fs/lockd/clntlock.c
*
* Lock handling for the client side NLM implementation
*
* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/time.h>
#include <linux/nfs_fs.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/smp_lock.h>
#define NLMDBG_FACILITY NLMDBG_CLIENT
/*
* Local function prototypes
*/
static int reclaimer(void *ptr);
/*
* The following functions handle blocking and granting from the
* client perspective.
*/
/*
* This is the representation of a blocked client lock.
*/
struct nlm_wait {
struct list_head b_list; /* linked list */
wait_queue_head_t b_wait; /* where to wait on */
struct nlm_host * b_host;
struct file_lock * b_lock; /* local file lock */
unsigned short b_reclaim; /* got to reclaim lock */
u32 b_status; /* grant callback status */
};
static LIST_HEAD(nlm_blocked);
/*
* Queue up a lock for blocking so that the GRANTED request can see it
*/
struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)
{
struct nlm_wait *block;
block = kmalloc(sizeof(*block), GFP_KERNEL);
if (block != NULL) {
block->b_host = host;
block->b_lock = fl;
init_waitqueue_head(&block->b_wait);
block->b_status = NLM_LCK_BLOCKED;
list_add(&block->b_list, &nlm_blocked);
}
return block;
}
void nlmclnt_finish_block(struct nlm_wait *block)
{
if (block == NULL)
return;
list_del(&block->b_list);
kfree(block);
}
/*
* Block on a lock
*/
int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)
{
long ret;
/* A borken server might ask us to block even if we didn't
* request it. Just say no!
*/
if (block == NULL)
return -EAGAIN;
/* Go to sleep waiting for GRANT callback. Some servers seem
* to lose callbacks, however, so we're going to poll from
* time to time just to make sure.
*
* For now, the retry frequency is pretty high; normally
* a 1 minute timeout would do. See the comment before
* nlmclnt_lock for an explanation.
*/
ret = wait_event_interruptible_timeout(block->b_wait,
block->b_status != NLM_LCK_BLOCKED,
timeout);
if (ret < 0)
return -ERESTARTSYS;
req->a_res.status = block->b_status;
return 0;
}
/*
* The server lockd has called us back to tell us the lock was granted
*/
u32 nlmclnt_grant(const struct sockaddr_in *addr, const struct nlm_lock *lock)
{
const struct file_lock *fl = &lock->fl;
const struct nfs_fh *fh = &lock->fh;
struct nlm_wait *block;
u32 res = nlm_lck_denied;
/*
* Look up blocked request based on arguments.
* Warning: must not use cookie to match it!
*/
list_for_each_entry(block, &nlm_blocked, b_list) {
struct file_lock *fl_blocked = block->b_lock;
if (fl_blocked->fl_start != fl->fl_start)
continue;
if (fl_blocked->fl_end != fl->fl_end)
continue;
/*
* Careful! The NLM server will return the 32-bit "pid" that
* we put on the wire: in this case the lockowner "pid".
*/
if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)
continue;
if (!nlm_cmp_addr(&block->b_host->h_addr, addr))
continue;
if (nfs_compare_fh(NFS_FH(fl_blocked->fl_file->f_dentry->d_inode) ,fh) != 0)
continue;
/* Alright, we found a lock. Set the return status
* and wake up the caller
*/
block->b_status = NLM_LCK_GRANTED;
wake_up(&block->b_wait);
res = nlm_granted;
}
return res;
}
/*
* The following procedures deal with the recovery of locks after a
* server crash.
*/
/*
* Someone has sent us an SM_NOTIFY. Ensure we bind to the new port number,
* that we mark locks for reclaiming, and that we bump the pseudo NSM state.
*/
static void nlmclnt_prepare_reclaim(struct nlm_host *host)
{
down_write(&host->h_rwsem);
host->h_monitored = 0;
host->h_state++;
host->h_nextrebind = 0;
nlm_rebind_host(host);
/*
* Mark the locks for reclaiming.
*/
list_splice_init(&host->h_granted, &host->h_reclaim);
dprintk("NLM: reclaiming locks for host %s", host->h_name);
}
static void nlmclnt_finish_reclaim(struct nlm_host *host)
{
host->h_reclaiming = 0;
up_write(&host->h_rwsem);
dprintk("NLM: done reclaiming locks for host %s", host->h_name);
}
/*
* Reclaim all locks on server host. We do this by spawning a separate
* reclaimer thread.
*/
void
nlmclnt_recovery(struct nlm_host *host, u32 newstate)
{
if (host->h_nsmstate == newstate)
return;
host->h_nsmstate = newstate;
if (!host->h_reclaiming++) {
nlm_get_host(host);
__module_get(THIS_MODULE);
if (kernel_thread(reclaimer, host, CLONE_KERNEL) < 0)
module_put(THIS_MODULE);
}
}
static int
reclaimer(void *ptr)
{
struct nlm_host *host = (struct nlm_host *) ptr;
struct nlm_wait *block;
struct file_lock *fl, *next;
u32 nsmstate;
daemonize("%s-reclaim", host->h_name);
allow_signal(SIGKILL);
/* This one ensures that our parent doesn't terminate while the
* reclaim is in progress */
lock_kernel();
lockd_up();
nlmclnt_prepare_reclaim(host);
/* First, reclaim all locks that have been marked. */
restart:
nsmstate = host->h_nsmstate;
list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
list_del_init(&fl->fl_u.nfs_fl.list);
if (signalled())
continue;
if (nlmclnt_reclaim(host, fl) != 0)
continue;
list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
if (host->h_nsmstate != nsmstate) {
/* Argh! The server rebooted again! */
list_splice_init(&host->h_granted, &host->h_reclaim);
goto restart;
}
}
nlmclnt_finish_reclaim(host);
/* Now, wake up all processes that sleep on a blocked lock */
list_for_each_entry(block, &nlm_blocked, b_list) {
if (block->b_host == host) {
block->b_status = NLM_LCK_DENIED_GRACE_PERIOD;
wake_up(&block->b_wait);
}
}
/* Release host handle after use */
nlm_release_host(host);
lockd_down();
unlock_kernel();
module_put_and_exit(0);
}