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authorSeth Forshee <seth.forshee@canonical.com>2016-03-11 10:35:34 -0600
committerMiklos Szeredi <miklos@szeredi.hu>2016-03-14 15:02:51 +0100
commit744742d692e37ad5c20630e57d526c8f2e2fe3c9 (patch)
treeef5965099fadc7d4c199a104e4715256afc53e9f /fs/fuse/cuse.c
parent7cabc61e01a0a8b663bd2b4c982aa53048218734 (diff)
fuse: Add reference counting for fuse_io_priv
The 'reqs' member of fuse_io_priv serves two purposes. First is to track the number of oustanding async requests to the server and to signal that the io request is completed. The second is to be a reference count on the structure to know when it can be freed. For sync io requests these purposes can be at odds. fuse_direct_IO() wants to block until the request is done, and since the signal is sent when 'reqs' reaches 0 it cannot keep a reference to the object. Yet it needs to use the object after the userspace server has completed processing requests. This leads to some handshaking and special casing that it needlessly complicated and responsible for at least one race condition. It's much cleaner and safer to maintain a separate reference count for the object lifecycle and to let 'reqs' just be a count of outstanding requests to the userspace server. Then we can know for sure when it is safe to free the object without any handshaking or special cases. The catch here is that most of the time these objects are stack allocated and should not be freed. Initializing these objects with a single reference that is never released prevents accidental attempts to free the objects. Fixes: 9d5722b7777e ("fuse: handle synchronous iocbs internally") Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/fuse/cuse.c')
-rw-r--r--fs/fuse/cuse.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 8e3ee1936c7e..c5b6b7165489 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -90,7 +90,7 @@ static struct list_head *cuse_conntbl_head(dev_t devt)
static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
{
- struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
+ struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb->ki_filp);
loff_t pos = 0;
return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE);
@@ -98,7 +98,7 @@ static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from)
{
- struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
+ struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb->ki_filp);
loff_t pos = 0;
/*
* No locking or generic_write_checks(), the server is