Attachment 202831 Details for Bug 280311 – NLM: Fix a circular lock dependency in lockd

[patch] NLM: Fix a circular lock dependency in lockd

linux-2.6.23-001-fix_lockd_circular_dependency.dif (text/plain), 3.38 KB, created by Trond Myklebust on 2007-09-21 20:51:25 UTC

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Creator: Trond Myklebust

Created: 2007-09-21 20:51:25 UTC

Size: 3.38 KB

patch

obsolete

>From: Trond Myklebust <Trond.Myklebust@netapp.com>
>Date: Wed, 19 Sep 2007 11:54:54 -0400
>NLM: Fix a circular lock dependency in lockd
>
>The problem is that the garbage collector for the 'host' structures
>nlm_gc_hosts(), holds nlm_host_mutex while calling down to
>nlmsvc_mark_resources, which, eventually takes the file->f_mutex.
>
>We cannot therefore call nlmsvc_lookup_host() from within
>nlmsvc_create_block, since the caller will already hold file->f_mutex, so
>the attempt to grab nlm_host_mutex may deadlock.
>
>Fix the problem by calling nlmsvc_lookup_host() outside the file->f_mutex.
>
>Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
>---
>
> fs/lockd/svclock.c |   29 ++++++++++++++++++-----------
> 1 files changed, 18 insertions(+), 11 deletions(-)
>
>diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
>index a21e4bc..d098c7a 100644
>--- a/fs/lockd/svclock.c
>+++ b/fs/lockd/svclock.c
>@@ -171,19 +171,14 @@ found:
>  * GRANTED_RES message by cookie, without having to rely on the client's IP
>  * address. --okir
>  */
>-static inline struct nlm_block *
>-nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
>-		struct nlm_lock *lock, struct nlm_cookie *cookie)
>+static struct nlm_block *
>+nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
>+		    struct nlm_file *file, struct nlm_lock *lock,
>+		    struct nlm_cookie *cookie)
> {
> 	struct nlm_block	*block;
>-	struct nlm_host		*host;
> 	struct nlm_rqst		*call = NULL;
> 
>-	/* Create host handle for callback */
>-	host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
>-	if (host == NULL)
>-		return NULL;
>-
> 	call = nlm_alloc_call(host);
> 	if (call == NULL)
> 		return NULL;
>@@ -366,6 +361,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> 			struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
> {
> 	struct nlm_block	*block = NULL;
>+	struct nlm_host		*host;
> 	int			error;
> 	__be32			ret;
> 
>@@ -377,6 +373,10 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> 				(long long)lock->fl.fl_end,
> 				wait);
> 
>+	/* Create host handle for callback */
>+	host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
>+	if (host == NULL)
>+		return nlm_lck_denied_nolocks;
> 
> 	/* Lock file against concurrent access */
> 	mutex_lock(&file->f_mutex);
>@@ -385,7 +385,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> 	 */
> 	block = nlmsvc_lookup_block(file, lock);
> 	if (block == NULL) {
>-		block = nlmsvc_create_block(rqstp, file, lock, cookie);
>+		block = nlmsvc_create_block(rqstp, nlm_get_host(host), file,
>+				lock, cookie);
> 		ret = nlm_lck_denied_nolocks;
> 		if (block == NULL)
> 			goto out;
>@@ -449,6 +450,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> out:
> 	mutex_unlock(&file->f_mutex);
> 	nlmsvc_release_block(block);
>+	nlm_release_host(host);
> 	dprintk("lockd: nlmsvc_lock returned %u\n", ret);
> 	return ret;
> }
>@@ -477,10 +479,15 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> 
> 	if (block == NULL) {
> 		struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
>+		struct nlm_host	*host;
> 
> 		if (conf == NULL)
> 			return nlm_granted;
>-		block = nlmsvc_create_block(rqstp, file, lock, cookie);
>+		/* Create host handle for callback */
>+		host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
>+		if (host == NULL)
>+			return nlm_lck_denied_nolocks;
>+		block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
> 		if (block == NULL) {
> 			kfree(conf);
> 			return nlm_granted;

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Attachments on bug 280311: 196301 | 202831 | 203001