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lockd: Add refcounting to struct nlm_block
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Otherwise, the block may disappear from underneath us when in
nlmsvc_retry_blocked.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Trond Myklebust authored and Trond Myklebust committed Mar 20, 2006
1 parent 09c7938 commit 6849c0c
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Showing 2 changed files with 47 additions and 50 deletions.
94 changes: 45 additions & 49 deletions fs/lockd/svclock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@
#define nlm_deadlock nlm_lck_denied
#endif

static void nlmsvc_release_block(struct nlm_block *block);
static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
static int nlmsvc_remove_block(struct nlm_block *block);

Expand All @@ -58,6 +59,7 @@ nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
struct nlm_block **bp, *b;

dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
kref_get(&block->b_count);
if (block->b_queued)
nlmsvc_remove_block(block);
bp = &nlm_blocked;
Expand Down Expand Up @@ -90,6 +92,7 @@ nlmsvc_remove_block(struct nlm_block *block)
if (b == block) {
*bp = block->b_next;
block->b_queued = 0;
nlmsvc_release_block(block);
return 1;
}
}
Expand Down Expand Up @@ -123,6 +126,7 @@ nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove)
*head = block->b_next;
block->b_queued = 0;
}
kref_get(&block->b_count);
return block;
}
}
Expand Down Expand Up @@ -155,6 +159,8 @@ nlmsvc_find_block(struct nlm_cookie *cookie, struct sockaddr_in *sin)
break;
}

if (block != NULL)
kref_get(&block->b_count);
return block;
}

Expand Down Expand Up @@ -188,6 +194,7 @@ nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
memset(block, 0, sizeof(*block));
locks_init_lock(&block->b_call.a_args.lock.fl);
locks_init_lock(&block->b_call.a_res.lock.fl);
kref_init(&block->b_count);

if (!nlmclnt_setgrantargs(&block->b_call, lock))
goto failed_free;
Expand Down Expand Up @@ -228,27 +235,24 @@ nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
* It is the caller's responsibility to check whether the file
* can be closed hereafter.
*/
static int
nlmsvc_delete_block(struct nlm_block *block)
static int nlmsvc_unlink_block(struct nlm_block *block)
{
struct file_lock *fl = &block->b_call.a_args.lock.fl;
struct nlm_file *file = block->b_file;
struct nlm_block **bp;
int status;

dprintk("lockd: deleting block %p...\n", block);
dprintk("lockd: unlinking block %p...\n", block);

/* Remove block from list */
status = posix_unblock_lock(block->b_file->f_file, &block->b_call.a_args.lock.fl);
nlmsvc_remove_block(block);
status = posix_unblock_lock(file->f_file, fl);
return status;
}

/* If the block is in the middle of a GRANT callback,
* don't kill it yet. */
if (block->b_incall) {
nlmsvc_insert_block(block, NLM_NEVER);
block->b_done = 1;
return status;
}
static void nlmsvc_free_block(struct kref *kref)
{
struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
struct nlm_file *file = block->b_file;
struct nlm_block **bp;

dprintk("lockd: freeing block %p...\n", block);

/* Remove block from file's list of blocks */
for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
Expand All @@ -262,7 +266,12 @@ nlmsvc_delete_block(struct nlm_block *block)
nlm_release_host(block->b_host);
nlmclnt_freegrantargs(&block->b_call);
kfree(block);
return status;
}

static void nlmsvc_release_block(struct nlm_block *block)
{
if (block != NULL)
kref_put(&block->b_count, nlmsvc_free_block);
}

/*
Expand All @@ -282,7 +291,7 @@ nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
block->b_host->h_inuse = 1;
else if (action == NLM_ACT_UNLOCK) {
if (host == NULL || host == block->b_host)
nlmsvc_delete_block(block);
nlmsvc_unlink_block(block);
}
}
up(&file->f_sema);
Expand Down Expand Up @@ -318,9 +327,9 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
block = nlmsvc_lookup_block(file, lock, 0);
if (block == NULL) {
if (newblock != NULL)
lock = &newblock->b_call.a_args.lock.fl;
lock = &newblock->b_call.a_args.lock;
} else
lock = &block->b_call.a_args.lock.fl;
lock = &block->b_call.a_args.lock;

error = posix_lock_file(file->f_file, &lock->fl);
lock->fl.fl_flags &= ~FL_SLEEP;
Expand Down Expand Up @@ -363,12 +372,10 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,

/* Append to list of blocked */
nlmsvc_insert_block(newblock, NLM_NEVER);
newblock = NULL;

out:
up(&file->f_sema);
if (newblock != NULL)
nlmsvc_delete_block(newblock);
nlmsvc_release_block(newblock);
nlmsvc_release_block(block);
dprintk("lockd: nlmsvc_lock returned %u\n", ret);
return ret;
}
Expand Down Expand Up @@ -450,8 +457,10 @@ nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
(long long)lock->fl.fl_end);

down(&file->f_sema);
if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL)
status = nlmsvc_delete_block(block);
if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL) {
status = nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
}
up(&file->f_sema);
return status ? nlm_lck_denied : nlm_granted;
}
Expand Down Expand Up @@ -514,7 +523,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
down(&file->f_sema);

/* Unlink block request from list */
nlmsvc_remove_block(block);
nlmsvc_unlink_block(block);

/* If b_granted is true this means we've been here before.
* Just retry the grant callback, possibly refreshing the RPC
Expand All @@ -525,7 +534,6 @@ nlmsvc_grant_blocked(struct nlm_block *block)
}

/* Try the lock operation again */
posix_unblock_lock(file->f_file, &lock->fl);
lock->fl.fl_flags |= FL_SLEEP;
error = posix_lock_file(file->f_file, &lock->fl);
lock->fl.fl_flags &= ~FL_SLEEP;
Expand All @@ -548,16 +556,15 @@ nlmsvc_grant_blocked(struct nlm_block *block)
/* Lock was granted by VFS. */
dprintk("lockd: GRANTing blocked lock.\n");
block->b_granted = 1;
block->b_incall = 1;

/* Schedule next grant callback in 30 seconds */
nlmsvc_insert_block(block, 30 * HZ);

/* Call the client */
nlm_get_host(block->b_call.a_host);
kref_get(&block->b_count);
if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
&nlmsvc_grant_ops) < 0)
nlm_release_host(block->b_call.a_host);
nlmsvc_release_block(block);
out_unlock:
up(&file->f_sema);
}
Expand All @@ -573,20 +580,10 @@ nlmsvc_grant_blocked(struct nlm_block *block)
static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
{
struct nlm_rqst *call = data;
struct nlm_block *block;
struct nlm_block *block = container_of(call, struct nlm_block, b_call);
unsigned long timeout;
struct sockaddr_in *peer_addr = RPC_PEERADDR(task->tk_client);

dprintk("lockd: GRANT_MSG RPC callback\n");
dprintk("callback: looking for cookie %s, host (%u.%u.%u.%u)\n",
nlmdbg_cookie2a(&call->a_args.cookie),
NIPQUAD(peer_addr->sin_addr.s_addr));
if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) {
dprintk("lockd: no block for cookie %s, host (%u.%u.%u.%u)\n",
nlmdbg_cookie2a(&call->a_args.cookie),
NIPQUAD(peer_addr->sin_addr.s_addr));
return;
}

/* Technically, we should down the file semaphore here. Since we
* move the block towards the head of the queue only, no harm
Expand All @@ -603,9 +600,7 @@ static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
}
nlmsvc_insert_block(block, timeout);
svc_wake_up(block->b_daemon);
block->b_incall = 0;

nlm_release_host(call->a_host);
nlmsvc_release_block(block);
}

static const struct rpc_call_ops nlmsvc_grant_ops = {
Expand All @@ -631,20 +626,19 @@ nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status

file->f_count++;
down(&file->f_sema);
block = nlmsvc_find_block(cookie, &rqstp->rq_addr);
if (block) {
if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
/* Try again in a couple of seconds */
nlmsvc_insert_block(block, 10 * HZ);
up(&file->f_sema);
} else {
/* Lock is now held by client, or has been rejected.
* In both cases, the block should be removed. */
nlmsvc_delete_block(block);
up(&file->f_sema);
nlmsvc_unlink_block(block);
}
}
up(&file->f_sema);
nlm_release_file(file);
nlmsvc_release_block(block);
}

/*
Expand All @@ -667,10 +661,12 @@ nlmsvc_retry_blocked(void)
break;
dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
block, block->b_when, block->b_done);
kref_get(&block->b_count);
if (block->b_done)
nlmsvc_delete_block(block);
nlmsvc_unlink_block(block);
else
nlmsvc_grant_blocked(block);
nlmsvc_release_block(block);
}

if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
Expand Down
3 changes: 2 additions & 1 deletion include/linux/lockd/lockd.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include <linux/config.h>
#include <linux/in.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/utsname.h>
#include <linux/nfsd/nfsfh.h>
#include <linux/lockd/bind.h>
Expand Down Expand Up @@ -110,6 +111,7 @@ struct nlm_file {
*/
#define NLM_NEVER (~(unsigned long) 0)
struct nlm_block {
struct kref b_count; /* Reference count */
struct nlm_block * b_next; /* linked list (all blocks) */
struct nlm_block * b_fnext; /* linked list (per file) */
struct nlm_rqst b_call; /* RPC args & callback info */
Expand All @@ -119,7 +121,6 @@ struct nlm_block {
unsigned int b_id; /* block id */
unsigned char b_queued; /* re-queued */
unsigned char b_granted; /* VFS granted lock */
unsigned char b_incall; /* doing callback */
unsigned char b_done; /* callback complete */
struct nlm_file * b_file; /* file in question */
};
Expand Down

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