| Message ID | 48a9d50b-f7b9-407d-06db-5c9079dfbf24@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix two bugs CB_NOTIFY_LOCK failing to wake a water | expand |
Hi Yihao, On 19/5/13 14:57, Yihao Wu wrote: > Commit b7dbcc0e433f "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" > found this bug. However it didn't fix it. > > This commit replaces schedule_timeout() with wait_woken() and > default_wake_function() with woken_wake_function() in function > nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses > memory barriers in its implementation to avoid potential race condition > when putting a process into sleeping state and then waking it up. > > Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks") > Cc: stable@vger.kernel.org #4.9+ > Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com> > --- > fs/nfs/nfs4proc.c | 23 +++++++---------------- > 1 file changed, 7 insertions(+), 16 deletions(-) > > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c > index c29cbef..f9ed6b5 100644 > --- a/fs/nfs/nfs4proc.c > +++ b/fs/nfs/nfs4proc.c > @@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter { > struct task_struct *task; > struct inode *inode; > struct nfs_lowner *owner; > - bool notified; > }; > > static int > @@ -6954,13 +6953,13 @@ struct nfs4_lock_waiter { > /* Make sure it's for the right inode */ > if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh)) > return 0; > - > - waiter->notified = true; > } > > /* override "private" so we can use default_wake_function */ > wait->private = waiter->task; > - ret = autoremove_wake_function(wait, mode, flags, key); > + ret = woken_wake_function(wait, mode, flags, key); > + if (ret) > + list_del_init(&wait->entry); > wait->private = waiter; > return ret; > } > @@ -6979,8 +6978,7 @@ struct nfs4_lock_waiter { > .s_dev = server->s_dev }; > struct nfs4_lock_waiter waiter = { .task = current, > .inode = state->inode, > - .owner = &owner, > - .notified = false }; > + .owner = &owner}; > wait_queue_entry_t wait; > > /* Don't bother with waitqueue if we don't expect a callback */ > @@ -6993,21 +6991,14 @@ struct nfs4_lock_waiter { > add_wait_queue(q, &wait); > > while(!signalled()) { > - waiter.notified = false; > status = nfs4_proc_setlk(state, cmd, request); > if ((status != -EAGAIN) || IS_SETLK(cmd)) > break; > > status = -ERESTARTSYS; > - spin_lock_irqsave(&q->lock, flags); > - if (waiter.notified) { > - spin_unlock_irqrestore(&q->lock, flags); > - continue; > - } > - set_current_state(TASK_INTERRUPTIBLE); > - spin_unlock_irqrestore(&q->lock, flags); > - > - freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT); > + freezer_do_not_count(); > + wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT); > + freezer_count(); Since now variable 'flags' is not used anymore, we have to delete it as well. Otherwise there is a compile warning “unused variable ‘flags’”. Thanks, Joseph > } > > finish_wait(q, &wait); >
On 2019/5/17 5:22 PM, Joseph Qi wrote: > Hi Yihao, > > On 19/5/13 14:57, Yihao Wu wrote: >> Commit b7dbcc0e433f "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" >> found this bug. However it didn't fix it. >> >> This commit replaces schedule_timeout() with wait_woken() and >> default_wake_function() with woken_wake_function() in function >> nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses >> memory barriers in its implementation to avoid potential race condition >> when putting a process into sleeping state and then waking it up. >> >> Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks") >> Cc: stable@vger.kernel.org #4.9+ >> Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com> >> --- >> fs/nfs/nfs4proc.c | 23 +++++++---------------- >> 1 file changed, 7 insertions(+), 16 deletions(-) >> >> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >> index c29cbef..f9ed6b5 100644 >> --- a/fs/nfs/nfs4proc.c >> +++ b/fs/nfs/nfs4proc.c >> @@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter { >> struct task_struct *task; >> struct inode *inode; >> struct nfs_lowner *owner; >> - bool notified; >> }; >> >> static int >> @@ -6954,13 +6953,13 @@ struct nfs4_lock_waiter { >> /* Make sure it's for the right inode */ >> if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh)) >> return 0; >> - >> - waiter->notified = true; >> } >> >> /* override "private" so we can use default_wake_function */ >> wait->private = waiter->task; >> - ret = autoremove_wake_function(wait, mode, flags, key); >> + ret = woken_wake_function(wait, mode, flags, key); >> + if (ret) >> + list_del_init(&wait->entry); >> wait->private = waiter; >> return ret; >> } >> @@ -6979,8 +6978,7 @@ struct nfs4_lock_waiter { >> .s_dev = server->s_dev }; >> struct nfs4_lock_waiter waiter = { .task = current, >> .inode = state->inode, >> - .owner = &owner, >> - .notified = false }; >> + .owner = &owner}; >> wait_queue_entry_t wait; >> >> /* Don't bother with waitqueue if we don't expect a callback */ >> @@ -6993,21 +6991,14 @@ struct nfs4_lock_waiter { >> add_wait_queue(q, &wait); >> >> while(!signalled()) { >> - waiter.notified = false; >> status = nfs4_proc_setlk(state, cmd, request); >> if ((status != -EAGAIN) || IS_SETLK(cmd)) >> break; >> >> status = -ERESTARTSYS; >> - spin_lock_irqsave(&q->lock, flags); >> - if (waiter.notified) { >> - spin_unlock_irqrestore(&q->lock, flags); >> - continue; >> - } >> - set_current_state(TASK_INTERRUPTIBLE); >> - spin_unlock_irqrestore(&q->lock, flags); >> - >> - freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT); >> + freezer_do_not_count(); >> + wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT); >> + freezer_count(); > > Since now variable 'flags' is not used anymore, we have to delete it as well. > Otherwise there is a compile warning “unused variable ‘flags’”. > > Thanks, > Joseph Thank you Joseph. I'll remove unused 'flags' in PATCH v3. Thanks, Yihao Wu > >> } >> >> finish_wait(q, &wait); >>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index c29cbef..f9ed6b5 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter { struct task_struct *task; struct inode *inode; struct nfs_lowner *owner; - bool notified; }; static int @@ -6954,13 +6953,13 @@ struct nfs4_lock_waiter { /* Make sure it's for the right inode */ if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh)) return 0; - - waiter->notified = true; } /* override "private" so we can use default_wake_function */ wait->private = waiter->task; - ret = autoremove_wake_function(wait, mode, flags, key); + ret = woken_wake_function(wait, mode, flags, key); + if (ret) + list_del_init(&wait->entry); wait->private = waiter; return ret; } @@ -6979,8 +6978,7 @@ struct nfs4_lock_waiter { .s_dev = server->s_dev }; struct nfs4_lock_waiter waiter = { .task = current, .inode = state->inode, - .owner = &owner, - .notified = false }; + .owner = &owner}; wait_queue_entry_t wait; /* Don't bother with waitqueue if we don't expect a callback */ @@ -6993,21 +6991,14 @@ struct nfs4_lock_waiter { add_wait_queue(q, &wait); while(!signalled()) { - waiter.notified = false; status = nfs4_proc_setlk(state, cmd, request); if ((status != -EAGAIN) || IS_SETLK(cmd)) break; status = -ERESTARTSYS; - spin_lock_irqsave(&q->lock, flags); - if (waiter.notified) { - spin_unlock_irqrestore(&q->lock, flags); - continue; - } - set_current_state(TASK_INTERRUPTIBLE); - spin_unlock_irqrestore(&q->lock, flags); - - freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT); + freezer_do_not_count(); + wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT); + freezer_count(); } finish_wait(q, &wait);
Commit b7dbcc0e433f "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" found this bug. However it didn't fix it. This commit replaces schedule_timeout() with wait_woken() and default_wake_function() with woken_wake_function() in function nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses memory barriers in its implementation to avoid potential race condition when putting a process into sleeping state and then waking it up. Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks") Cc: stable@vger.kernel.org #4.9+ Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com> --- fs/nfs/nfs4proc.c | 23 +++++++---------------- 1 file changed, 7 insertions(+), 16 deletions(-)