Commit 153a9961 authored by David Howells's avatar David Howells
Browse files

netfs: Implement unbuffered/DIO write support 



Implement support for unbuffered writes and direct I/O writes.  If the
write is misaligned with respect to the fscrypt block size, then RMW cycles
are performed if necessary.  DIO writes are a special case of unbuffered
writes with extra restriction imposed, such as block size alignment
requirements.

Also provide a field that can tell the code to add some extra space onto
the bounce buffer for use by the filesystem in the case of a
content-encrypted file.

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 016dc851

fs/afs/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -250,7 +250,7 @@ static void afs_apply_status(struct afs_operation *op, 
		 * what's on the server.

		 */

		vnode->netfs.remote_i_size = status->size;

		if (change_size) {

		if (change_size || status->size > i_size_read(inode)) {

			afs_set_i_size(vnode, status->size);

			inode_set_ctime_to_ts(inode, t);

			inode_set_atime_to_ts(inode, t);

fs/netfs/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ netfs-y := \ 
	buffered_read.o \

	buffered_write.o \

	direct_read.o \

	direct_write.o \

	io.o \

	iterator.o \

	locking.o \

fs/netfs/direct_write.c

0 → 100644
+166 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later

/* Unbuffered and direct write support.

 *

 * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.

 * Written by David Howells (dhowells@redhat.com)

 */



#include <linux/export.h>

#include <linux/uio.h>

#include "internal.h"



static void netfs_cleanup_dio_write(struct netfs_io_request *wreq)

{

	struct inode *inode = wreq->inode;

	unsigned long long end = wreq->start + wreq->len;



	if (!wreq->error &&

	    i_size_read(inode) < end) {

		if (wreq->netfs_ops->update_i_size)

			wreq->netfs_ops->update_i_size(inode, end);

		else

			i_size_write(inode, end);

	}

}



/*

 * Perform an unbuffered write where we may have to do an RMW operation on an

 * encrypted file.  This can also be used for direct I/O writes.

 */

ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *iter,

					   struct netfs_group *netfs_group)

{

	struct netfs_io_request *wreq;

	unsigned long long start = iocb->ki_pos;

	unsigned long long end = start + iov_iter_count(iter);

	ssize_t ret, n;

	bool async = !is_sync_kiocb(iocb);



	_enter("");



	/* We're going to need a bounce buffer if what we transmit is going to

	 * be different in some way to the source buffer, e.g. because it gets

	 * encrypted/compressed or because it needs expanding to a block size.

	 */

	// TODO



	_debug("uw %llx-%llx", start, end);



	wreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp,

				   start, end - start,

				   iocb->ki_flags & IOCB_DIRECT ?

				   NETFS_DIO_WRITE : NETFS_UNBUFFERED_WRITE);

	if (IS_ERR(wreq))

		return PTR_ERR(wreq);



	{

		/* If this is an async op and we're not using a bounce buffer,

		 * we have to save the source buffer as the iterator is only

		 * good until we return.  In such a case, extract an iterator

		 * to represent as much of the the output buffer as we can

		 * manage.  Note that the extraction might not be able to

		 * allocate a sufficiently large bvec array and may shorten the

		 * request.

		 */

		if (async || user_backed_iter(iter)) {

			n = netfs_extract_user_iter(iter, wreq->len, &wreq->iter, 0);

			if (n < 0) {

				ret = n;

				goto out;

			}

			wreq->direct_bv = (struct bio_vec *)wreq->iter.bvec;

			wreq->direct_bv_count = n;

			wreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);

			wreq->len = iov_iter_count(&wreq->iter);

		} else {

			wreq->iter = *iter;

		}



		wreq->io_iter = wreq->iter;

	}



	/* Copy the data into the bounce buffer and encrypt it. */

	// TODO



	/* Dispatch the write. */

	__set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq->flags);

	if (async)

		wreq->iocb = iocb;

	wreq->cleanup = netfs_cleanup_dio_write;

	ret = netfs_begin_write(wreq, is_sync_kiocb(iocb),

				iocb->ki_flags & IOCB_DIRECT ?

				netfs_write_trace_dio_write :

				netfs_write_trace_unbuffered_write);

	if (ret < 0) {

		_debug("begin = %zd", ret);

		goto out;

	}



	if (!async) {

		trace_netfs_rreq(wreq, netfs_rreq_trace_wait_ip);

		wait_on_bit(&wreq->flags, NETFS_RREQ_IN_PROGRESS,

			    TASK_UNINTERRUPTIBLE);



		ret = wreq->error;

		_debug("waited = %zd", ret);

		if (ret == 0) {

			ret = wreq->transferred;

			iocb->ki_pos += ret;

		}

	} else {

		ret = -EIOCBQUEUED;

	}



out:

	netfs_put_request(wreq, false, netfs_rreq_trace_put_return);

	return ret;

}



/**

 * netfs_unbuffered_write_iter - Unbuffered write to a file

 * @iocb: IO state structure

 * @from: iov_iter with data to write

 *

 * Do an unbuffered write to a file, writing the data directly to the server

 * and not lodging the data in the pagecache.

 *

 * Return:

 * * Negative error code if no data has been written at all of

 *   vfs_fsync_range() failed for a synchronous write

 * * Number of bytes written, even for truncated writes

 */

ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;

	struct netfs_inode *ictx = netfs_inode(inode);

	ssize_t ret;



	_enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read(inode));



	trace_netfs_write_iter(iocb, from);



	ret = netfs_start_io_direct(inode);

	if (ret < 0)

		return ret;

	ret = generic_write_checks(iocb, from);

	if (ret < 0)

		goto out;

	ret = file_remove_privs(file);

	if (ret < 0)

		goto out;

	ret = file_update_time(file);

	if (ret < 0)

		goto out;

	ret = kiocb_invalidate_pages(iocb, iov_iter_count(from));

	if (ret < 0)

		goto out;



	fscache_invalidate(netfs_i_cookie(ictx), NULL, i_size_read(inode),

			   FSCACHE_INVAL_DIO_WRITE);

	ret = netfs_unbuffered_write_iter_locked(iocb, from, NULL);

out:

	netfs_end_io_direct(inode);

	return ret;

}

EXPORT_SYMBOL(netfs_unbuffered_write_iter);

fs/netfs/internal.h

+6 −0
Original line number Diff line number Diff line
@@ -26,6 +26,12 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq); 
int netfs_prefetch_for_write(struct file *file, struct folio *folio,

			     size_t offset, size_t len);



/*

 * direct_write.c

 */

ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *iter,

					   struct netfs_group *netfs_group);



/*

 * io.c

 */

fs/netfs/io.c

+1 −1
Original line number Diff line number Diff line
@@ -645,7 +645,7 @@ static bool netfs_rreq_submit_slice(struct netfs_io_request *rreq, 


	subreq->debug_index	= (*_debug_index)++;

	subreq->start		= rreq->start + rreq->submitted;

	subreq->len		= rreq->len   - rreq->submitted;

	subreq->len		= io_iter->count;



	_debug("slice %llx,%zx,%zx", subreq->start, subreq->len, rreq->submitted);

	list_add_tail(&subreq->rreq_link, &rreq->subrequests);