Commit 21d706d5 authored by David Howells's avatar David Howells
Browse files

netfs: Add support for DIO buffering 



Add a bvec array pointer and an iterator to netfs_io_request for either
holding a copy of a DIO iterator or a list of all the bits of buffer
pointed to by a DIO iterator.

There are two problems:  Firstly, if an iovec-class iov_iter is passed to
->read_iter() or ->write_iter(), this cannot be passed directly to
kernel_sendmsg() or kernel_recvmsg() as that may cause locking recursion if
a fault is generated, so we need to keep track of the pages involved
separately.

Secondly, if the I/O is asynchronous, we must copy the iov_iter describing
the buffer before returning to the caller as it may be immediately
deallocated.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
parent 92b6cc5d

fs/netfs/objects.c

+10 −0
Original line number Diff line number Diff line
@@ -76,6 +76,7 @@ static void netfs_free_request(struct work_struct *work) 
{

	struct netfs_io_request *rreq =

		container_of(work, struct netfs_io_request, work);

	unsigned int i;



	trace_netfs_rreq(rreq, netfs_rreq_trace_free);

	netfs_proc_del_rreq(rreq);
@@ -84,6 +85,15 @@ static void netfs_free_request(struct work_struct *work) 
		rreq->netfs_ops->free_request(rreq);

	if (rreq->cache_resources.ops)

		rreq->cache_resources.ops->end_operation(&rreq->cache_resources);

	if (rreq->direct_bv) {

		for (i = 0; i < rreq->direct_bv_count; i++) {

			if (rreq->direct_bv[i].bv_page) {

				if (rreq->direct_bv_unpin)

					unpin_user_page(rreq->direct_bv[i].bv_page);

			}

		}

		kvfree(rreq->direct_bv);

	}

	kfree_rcu(rreq, rcu);

	netfs_stat_d(&netfs_n_rh_rreq);

}

include/linux/netfs.h

+3 −0
Original line number Diff line number Diff line
@@ -190,6 +190,8 @@ struct netfs_io_request { 
	struct iov_iter		iter;		/* Unencrypted-side iterator */

	struct iov_iter		io_iter;	/* I/O (Encrypted-side) iterator */

	void			*netfs_priv;	/* Private data for the netfs */

	struct bio_vec		*direct_bv;	/* DIO buffer list (when handling iovec-iter) */

	unsigned int		direct_bv_count; /* Number of elements in direct_bv[] */

	unsigned int		debug_id;

	atomic_t		nr_outstanding;	/* Number of ops in progress */

	atomic_t		nr_copy_ops;	/* Number of copy-to-cache ops in progress */
@@ -197,6 +199,7 @@ struct netfs_io_request { 
	size_t			len;		/* Length of the request */

	short			error;		/* 0 or error that occurred */

	enum netfs_io_origin	origin;		/* Origin of the request */

	bool			direct_bv_unpin; /* T if direct_bv[] must be unpinned */

	loff_t			i_size;		/* Size of the file */

	loff_t			start;		/* Start position */

	pgoff_t			no_unlock_folio; /* Don't unlock this folio after read */