> On Mar 24, 2015, at 10:29 PM, Steve French <smfrench@xxxxxxxxx> wrote: > > On Tue, Mar 24, 2015 at 7:18 PM, Chengyu Song <csong84@xxxxxxxxxx> wrote: >> posix_lock_file_wait may fail under certain circumstances, and its result is >> usually checked/returned. But given the complexity of cifs, I'm not sure if >> the result is intentially left unchecked and always expected to succeed. >> >> Signed-off-by: Chengyu Song <csong84@xxxxxxxxxx> >> --- >> fs/cifs/file.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/fs/cifs/file.c b/fs/cifs/file.c >> index a94b3e6..beef67b 100644 >> --- a/fs/cifs/file.c >> +++ b/fs/cifs/file.c >> @@ -1553,8 +1553,8 @@ cifs_setlk(struct file *file, struct file_lock *flock, __u32 type, >> rc = server->ops->mand_unlock_range(cfile, flock, xid); >> >> out: >> - if (flock->fl_flags & FL_POSIX) >> - posix_lock_file_wait(file, flock); >> + if (flock->fl_flags & FL_POSIX && !rc) >> + rc = posix_lock_file_wait(file, flock); >> return rc; >> } >> > > This is interesting. Useful comparisons include > > For network file systems you could > - enforce byte range locks only at the server > - enforce locks only on the client, and don't send to the server > - do both > > Since cifs byte range locks are often emulated (except when Unix > Extensions are enabled, e.g. on mounts to Samba), we do the latter by > default, as does fs/9p (although they do it in a different order, > trying to grab the local byte range lock first). > > But another interesting comparison point is nfs, where the code for v3 > vs. v4 looks different. Take a look at nfsv3 (see fs/nfs/file.c) where > the choice is made to either do the posix_lock_file_wait (if 'local' > locking only) or if sending locks to the server then don't call to set > the local lock. Alternatively nfs4proc.c handles it differently. > > There may not be a perfect answer on this one but was wondering if you > have experimented with what happens when you mount with "nobrl" (which > is the cifs mount option which causes locks not to be sent to the > server, and thus only evaulted locally). My suspicion is that you can > demonstrate a failure if you mount with nobrl (without your patch). > Maybe it's better to provide more context. We're developing a static checker that cross check different implementations of filesystems, and this is a warning we get from that tool as it is the only place where the return value of posix_lock_file_wait is not checked/forwarded. So I have not experimented with mounting options. And I guess another thing is, for the path of posix_lock == false, posix_lock_file_wait is never invoked if any error happens. But for CIFSSMBPosixLock, its return value is never checked and posix_lock_file_wait is always invoked. Thanks, Chengyu-- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
