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virtiofsd: Do not support blocking flock 

With the current implementation, blocking flock can lead to
deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
to perform a blocking flock request.

Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
Message-Id: <20220113153249.710216-1-sebastian.hasler@stuvus.uni-stuttgart.de>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
This commit is contained in:
Sebastian Hasler 2022-01-13 16:32:49 +01:00 committed by Dr. David Alan Gilbert
parent c13b8e9973
commit 41af4459ac
1 changed files with 9 additions and 0 deletions
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9
tools/virtiofsd/passthrough_ll.c
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@ -2467,6 +2467,15 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
int res;
(void)ino;
if (!(op & LOCK_NB)) {
/*
* Blocking flock can deadlock as there is only one thread
* serving the queue.
*/
fuse_reply_err(req, EOPNOTSUPP);
return;
}
res = flock(lo_fi_fd(req, fi), op);
fuse_reply_err(req, res == -1 ? errno : 0);