@@ -67,7 +67,7 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
* allocate a sufficiently large bvec array and may shorten the
* request.
*/
- if (async || user_backed_iter(iter)) {
+ if (user_backed_iter(iter)) {
n = netfs_extract_user_iter(iter, len, &wreq->iter, 0);
if (n < 0) {
ret = n;
@@ -77,6 +77,11 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
wreq->direct_bv_count = n;
wreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);
} else {
+ /* If this is a kernel-generated async DIO request,
+ * assume that any resources the iterator points to
+ * (eg. a bio_vec array) will persist till the end of
+ * the op.
+ */
wreq->iter = *iter;
}
Netfslib needs to be able to handle kernel-initiated asynchronous DIO that is supplied with a bio_vec[] array. Currently, because of the async flag, this gets passed to netfs_extract_user_iter() which throws a warning and fails because it only handles IOVEC and UBUF iterators. This can be triggered through a combination of cifs and a loopback blockdev with something like: mount //my/cifs/share /foo dd if=/dev/zero of=/foo/m0 bs=4K count=1K losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0 echo hello >/dev/loop2046 This causes the following to appear in syslog: WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs] and the write to fail. Fix this by removing the check in netfs_unbuffered_write_iter_locked() that causes async kernel DIO writes to be handled as userspace writes. Note that this change relies on the kernel caller maintaining the existence of the bio_vec array (or kvec[] or folio_queue) until the op is complete. Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support") Reported-by: Nicolas Baranger <nicolas.baranger@3xo.fr> Closes: https://lore.kernel.org/r/fedd8a40d54b2969097ffa4507979858@3xo.fr/ Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Nicolas Baranger <nicolas.baranger@3xo.fr> Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com> cc: Steve French <smfrench@gmail.com> cc: Jeff Layton <jlayton@kernel.org> cc: netfs@lists.linux.dev cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org --- fs/netfs/direct_write.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)