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author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2007-09-25 21:55:03 +0200 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-09-26 18:22:04 +0200 |
commit | 255129d1e9ca0ed3d69d5517fae3e03d7ab4b806 (patch) | |
tree | e3dedbffebd4f0e15da97684500296c9bc4d3d6a /fs/lockd | |
parent | lguest example launcher truncates block device file to 0 length on problems (diff) | |
download | linux-255129d1e9ca0ed3d69d5517fae3e03d7ab4b806.tar.xz linux-255129d1e9ca0ed3d69d5517fae3e03d7ab4b806.zip |
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>
Diffstat (limited to 'fs/lockd')
-rw-r--r-- | 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 a21e4bc5444b..d098c7af0d22 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; |