On 04/28/2016 01:40 PM, Olga Kornievskaia wrote: > On Thu, Apr 28, 2016 at 1:22 PM, Anna Schumaker > <Anna.Schumaker@xxxxxxxxxx> wrote: >> On 04/28/2016 12:05 PM, Chuck Lever wrote: >>> >>>> On Apr 28, 2016, at 11:56 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >>>> >>>> Chuck or Anna, >>>> >>>> If the patch is accepted, do you mind expanding the commit message to >>>> include the wording about the LOCK and CB_RECALL race (so that it's >>>> documented to look back into it). >>> >>> Anna's choice. >> >> Sounds like a good idea. Is there any particular wording that you want? If not, then I can try to base something off of your email from Tuesday (4/26). > > No particular wording. Could be as little as: "helps with LOCK and > CB_RECALL race" or could include my explanation of what happens from > Tuesday. Okay, how does this look? http://git.linux-nfs.org/?p=anna/linux-nfs.git;a=commit;h=aa56ecf86281edd8dd488484596675813928f140 As a side note, I just put together a [testing] branch with this patch and all the others I could find from the last month or so. Please let me know if it looks like I'm missing anything! Thanks, Anna > >> >> Anna >> >>> >>> >>>> On Thu, Apr 28, 2016 at 10:09 AM, Anna Schumaker >>>> <Anna.Schumaker@xxxxxxxxxx> wrote: >>>>> On 04/28/2016 10:06 AM, Chuck Lever wrote: >>>>>> >>>>>>> On Apr 28, 2016, at 9:13 AM, Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> wrote: >>>>>>> >>>>>>> The patch looks pretty straightforward to me, and it sounds like it fixes a few problems that people are seeing. One question (below): >>>>>>> >>>>>>> On 04/28/2016 08:43 AM, William Dauchy wrote: >>>>>>>> Hello Anna, >>>>>>>> >>>>>>>> Could you have a look at this one please? >>>>>>>> >>>>>>>> Thanks, >>>>>>>> >>>>>>>> William >>>>>>>> >>>>>>>> On Tue, Apr 26, 2016 at 4:24 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >>>>>>>>> I believe this patch also helps with a race between a LOCK and >>>>>>>>> CB_RECALL. Application does a lock as the delegation is being >>>>>>>>> recalled. The lock thread sees the delegated state and acquires a >>>>>>>>> local lock. At the same time delegation doesn't see it the lock yet >>>>>>>>> and returns the delegation. Application proceeds to do IO. It ends up >>>>>>>>> using an open stateid for the IO (as there is no delegation stateid or >>>>>>>>> lock stateid). The server is unaware of the lock so it can give that >>>>>>>>> lock to somebody else. Yet this client thinks it has a local lock. It >>>>>>>>> leads to inconsistent data between clients. >>>>>>>>> >>>>>>>>> On Mon, Apr 11, 2016 at 4:20 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: >>>>>>>>>> At Connectathon 2016, we found that recent upstream Linux clients >>>>>>>>>> would occasionally send a LOCK operation with a zero stateid. This >>>>>>>>>> appeared to happen in close proximity to another thread returning >>>>>>>>>> a delegation before unlinking the same file while it remained open. >>>>>>>>>> >>>>>>>>>> Earlier, the client received a write delegation on this file and >>>>>>>>>> returned the open stateid. Now, as it is getting ready to unlink the >>>>>>>>>> file, it returns the write delegation. But there is still an open >>>>>>>>>> file descriptor on that file, so the client must OPEN the file >>>>>>>>>> again before it returns the delegation. >>>>>>>>>> >>>>>>>>>> Since commit 24311f884189 ('NFSv4: Recovery of recalled read >>>>>>>>>> delegations is broken'), nfs_open_delegation_recall() clears the >>>>>>>>>> NFS_DELEGATED_STATE flag _before_ it sends the OPEN. This allows a >>>>>>>>>> racing LOCK on the same inode to be put on the wire before the OPEN >>>>>>>>>> operation has returned a valid open stateid. >>>>>>>>>> >>>>>>>>>> To eliminate this race, serialize delegation return with the >>>>>>>>>> acquisition of a file lock on the same file. Adopt the same approach >>>>>>>>>> as is used in the unlock path. >>>>>>>>>> >>>>>>>>>> Fixes: 24311f884189 ('NFSv4: Recovery of recalled read ... ') >>>>>>>>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> >>>>>>>>>> --- >>>>>>>>>> Hi- >>>>>>>>>> >>>>>>>>>> This fix appears to be both safe and effective. Please consider >>>>>>>>>> it for v4.7 and for stable. Thanks! >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> fs/nfs/nfs4proc.c | 4 ++++ >>>>>>>>>> 1 file changed, 4 insertions(+) >>>>>>>>>> >>>>>>>>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >>>>>>>>>> index 01bef06..c40f1b6 100644 >>>>>>>>>> --- a/fs/nfs/nfs4proc.c >>>>>>>>>> +++ b/fs/nfs/nfs4proc.c >>>>>>>>>> @@ -6054,6 +6054,7 @@ static int nfs41_lock_expired(struct nfs4_state *state, struct file_lock *reques >>>>>>>>>> static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock *request) >>>>>>>>>> { >>>>>>>>>> struct nfs_inode *nfsi = NFS_I(state->inode); >>>>>>>>>> + struct nfs4_state_owner *sp = state->owner; >>>>>>>>>> unsigned char fl_flags = request->fl_flags; >>>>>>>>>> int status = -ENOLCK; >>>>>>>>>> >>>>>>>>>> @@ -6068,6 +6069,7 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock >>>>>>>>>> status = do_vfs_lock(state->inode, request); >>>>>>>>>> if (status < 0) >>>>>>>>>> goto out; >>>>>>>>>> + mutex_lock(&sp->so_delegreturn_mutex); >>>>>>> >>>>>>> From what I can tell, the first call to do_vfs_lock() in this function is used to test if we can take the lock locally. Do we need to worry about this racing with delegreturn, too? >>>>>> >>>>>> When I included that call in the critical section, >>>>>> cthon04 locking tests deadlocked. >>>>> >>>>> Got it. Thanks for checking! >>>>> >>>>> Anna >>>>> >>>>>> >>>>>> >>>>>>> Thanks, >>>>>>> Anna >>>>>>> >>>>>>>>>> down_read(&nfsi->rwsem); >>>>>>>>>> if (test_bit(NFS_DELEGATED_STATE, &state->flags)) { >>>>>>>>>> /* Yes: cache locks! */ >>>>>>>>>> @@ -6075,9 +6077,11 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock >>>>>>>>>> request->fl_flags = fl_flags & ~FL_SLEEP; >>>>>>>>>> status = do_vfs_lock(state->inode, request); >>>>>>>>>> up_read(&nfsi->rwsem); >>>>>>>>>> + mutex_unlock(&sp->so_delegreturn_mutex); >>>>>>>>>> goto out; >>>>>>>>>> } >>>>>>>>>> up_read(&nfsi->rwsem); >>>>>>>>>> + mutex_unlock(&sp->so_delegreturn_mutex); >>>>>>>>>> status = _nfs4_do_setlk(state, cmd, request, NFS_LOCK_NEW); >>>>>>>>>> out: >>>>>>>>>> request->fl_flags = fl_flags; >>>>>> >>>>>> -- >>>>>> Chuck Lever >>>>>> >>>>>> >>>>>> >>>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >>> -- >>> Chuck Lever >>> >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
