| Message ID | bdd6f570-f387-0371-09fb-d7b8c9993e8b@virtuozzo.com |
|---|---|
| State | New |
| Headers | show |
| Series | ksmbd: force "fail immediately" flag on fs with its own ->lock | expand |
2021-12-17 20:23 GMT+09:00, Vasily Averin <vvs@virtuozzo.com>: > Like nfsd and lockd, ksmbd can cause deadlock if the exported > file system does not support asynchronous processing of blocking locks: > if all ksmbd worker threads handles such requests, > they can never finish and the server will not be able to handle > any other incoming requests. > > Any filesystem that leaves ->lock NULL will use posix_lock_file(), which > does the right thing. Simplest is just to assume that any filesystem > that defines its own ->lock is not safe to request a blocking lock from. > > To work around the problem we need to drop fl->fl_flag FL_SLEEP before > vfs_lock_file() execution, it forces affected functions to avoid blocking. > > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Acked-by: Namjae Jeon <linkinjeon@kernel.org> Thanks! > --- > fs/ksmbd/smb2pdu.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c > index 121f8e8c70ac..f2225491af02 100644 > --- a/fs/ksmbd/smb2pdu.c > +++ b/fs/ksmbd/smb2pdu.c > @@ -6634,6 +6634,12 @@ static int smb2_set_flock_flags(struct file_lock > *flock, int flags) > { > int cmd = -EINVAL; > > + if ((flock->fl_file->f_op->lock) && > + ((flags == SMB2_LOCKFLAG_SHARED) || > + (flags == SMB2_LOCKFLAG_EXCLUSIVE))) { > + ksmbd_debug(SMB, "force fail immediately request\n"); > + flags |= SMB2_LOCKFLAG_FAIL_IMMEDIATELY; > + } > /* Checking for wrong flag combination during lock request*/ > switch (flags) { > case SMB2_LOCKFLAG_SHARED: > -- > 2.25.1 > >
diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c index 121f8e8c70ac..f2225491af02 100644 --- a/fs/ksmbd/smb2pdu.c +++ b/fs/ksmbd/smb2pdu.c @@ -6634,6 +6634,12 @@ static int smb2_set_flock_flags(struct file_lock *flock, int flags) { int cmd = -EINVAL; + if ((flock->fl_file->f_op->lock) && + ((flags == SMB2_LOCKFLAG_SHARED) || + (flags == SMB2_LOCKFLAG_EXCLUSIVE))) { + ksmbd_debug(SMB, "force fail immediately request\n"); + flags |= SMB2_LOCKFLAG_FAIL_IMMEDIATELY; + } /* Checking for wrong flag combination during lock request*/ switch (flags) { case SMB2_LOCKFLAG_SHARED:
Like nfsd and lockd, ksmbd can cause deadlock if the exported file system does not support asynchronous processing of blocking locks: if all ksmbd worker threads handles such requests, they can never finish and the server will not be able to handle any other incoming requests. Any filesystem that leaves ->lock NULL will use posix_lock_file(), which does the right thing. Simplest is just to assume that any filesystem that defines its own ->lock is not safe to request a blocking lock from. To work around the problem we need to drop fl->fl_flag FL_SLEEP before vfs_lock_file() execution, it forces affected functions to avoid blocking. Signed-off-by: Vasily Averin <vvs@virtuozzo.com> --- fs/ksmbd/smb2pdu.c | 6 ++++++ 1 file changed, 6 insertions(+)