Commit 938e13a7 authored by David Howells's avatar David Howells
Browse files

netfs: Implement buffered write API 



Institute a netfs write helper, netfs_file_write_iter(), to be pointed at
by the network filesystem ->write_iter() call.  Make it handled buffered
writes by calling the previously defined netfs_perform_write() to copy the
source data into the pagecache.

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 153a9961

fs/netfs/buffered_write.c

+83 −0
Original line number Diff line number Diff line
@@ -333,3 +333,86 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, 
	goto out;

}

EXPORT_SYMBOL(netfs_perform_write);



/**

 * netfs_buffered_write_iter_locked - write data to a file

 * @iocb:	IO state structure (file, offset, etc.)

 * @from:	iov_iter with data to write

 * @netfs_group: Grouping for dirty pages (eg. ceph snaps).

 *

 * This function does all the work needed for actually writing data to a

 * file. It does all basic checks, removes SUID from the file, updates

 * modification times and calls proper subroutines depending on whether we

 * do direct IO or a standard buffered write.

 *

 * The caller must hold appropriate locks around this function and have called

 * generic_write_checks() already.  The caller is also responsible for doing

 * any necessary syncing afterwards.

 *

 * This function does *not* take care of syncing data in case of O_SYNC write.

 * A caller has to handle it. This is mainly due to the fact that we want to

 * avoid syncing under i_rwsem.

 *

 * Return:

 * * number of bytes written, even for truncated writes

 * * negative error code if no data has been written at all

 */

ssize_t netfs_buffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *from,

					 struct netfs_group *netfs_group)

{

	struct file *file = iocb->ki_filp;

	ssize_t ret;



	trace_netfs_write_iter(iocb, from);



	ret = file_remove_privs(file);

	if (ret)

		return ret;



	ret = file_update_time(file);

	if (ret)

		return ret;



	return netfs_perform_write(iocb, from, netfs_group);

}

EXPORT_SYMBOL(netfs_buffered_write_iter_locked);



/**

 * netfs_file_write_iter - write data to a file

 * @iocb: IO state structure

 * @from: iov_iter with data to write

 *

 * Perform a write to a file, writing into the pagecache if possible and doing

 * an unbuffered write instead if not.

 *

 * 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_file_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));



	if ((iocb->ki_flags & IOCB_DIRECT) ||

	    test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))

		return netfs_unbuffered_write_iter(iocb, from);



	ret = netfs_start_io_write(inode);

	if (ret < 0)

		return ret;



	ret = generic_write_checks(iocb, from);

	if (ret > 0)

		ret = netfs_buffered_write_iter_locked(iocb, from, NULL);

	netfs_end_io_write(inode);

	if (ret > 0)

		ret = generic_write_sync(iocb, ret);

	return ret;

}

EXPORT_SYMBOL(netfs_file_write_iter);

include/linux/netfs.h

+3 −0
Original line number Diff line number Diff line
@@ -382,7 +382,10 @@ ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter); 
/* High-level write API */

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

			    struct netfs_group *netfs_group);

ssize_t netfs_buffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *from,

					 struct netfs_group *netfs_group);

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

ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from);



/* Address operations API */

struct readahead_control;