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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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Trond Myklebust 2007-09-25 15:55:03 -04:00 committed by Linus Torvalds
parent f6a592e8ab
commit 255129d1e9
1 changed files with 18 additions and 11 deletions
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29
fs/lockd/svclock.c
View File

@ -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;