linux/fs/ceph/ioctl.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef FS_CEPH_IOCTL_H
#define FS_CEPH_IOCTL_H

#include <linux/ioctl.h>
#include <linux/types.h>

#define CEPH_IOCTL_MAGIC …

/*
 * CEPH_IOC_GET_LAYOUT - get file layout or dir layout policy
 * CEPH_IOC_SET_LAYOUT - set file layout
 * CEPH_IOC_SET_LAYOUT_POLICY - set dir layout policy
 *
 * The file layout specifies how file data is striped over objects in
 * the distributed object store, which object pool they belong to (if
 * it differs from the default), and an optional 'preferred osd' to
 * store them on.
 *
 * Files get a new layout based on the policy set on the containing
 * directory or one of its ancestors.  The GET_LAYOUT ioctl will let
 * you examine the layout for a file or the policy on a directory.
 *
 * SET_LAYOUT will let you set a layout on a newly created file.  This
 * only works immediately after the file is created and before any
 * data is written to it.
 *
 * SET_LAYOUT_POLICY will let you set a layout policy (default layout)
 * on a directory that will apply to any new files created in that
 * directory (or any child directory that doesn't specify a layout of
 * its own).
 */

/* use u64 to align sanely on all archs */
struct ceph_ioctl_layout { … };

#define CEPH_IOC_GET_LAYOUT …
#define CEPH_IOC_SET_LAYOUT …
#define CEPH_IOC_SET_LAYOUT_POLICY …

/*
 * CEPH_IOC_GET_DATALOC - get location of file data in the cluster
 *
 * Extract identity, address of the OSD and object storing a given
 * file offset.
 */
struct ceph_ioctl_dataloc { … };

#define CEPH_IOC_GET_DATALOC …

/*
 * CEPH_IOC_LAZYIO - relax consistency
 *
 * Normally Ceph switches to synchronous IO when multiple clients have
 * the file open (and or more for write).  Reads and writes bypass the
 * page cache and go directly to the OSD.  Setting this flag on a file
 * descriptor will allow buffered IO for this file in cases where the
 * application knows it won't interfere with other nodes (or doesn't
 * care).
 */
#define CEPH_IOC_LAZYIO …

/*
 * CEPH_IOC_SYNCIO - force synchronous IO
 *
 * This ioctl sets a file flag that forces the synchronous IO that
 * bypasses the page cache, even if it is not necessary.  This is
 * essentially the opposite behavior of IOC_LAZYIO.  This forces the
 * same read/write path as a file opened by multiple clients when one
 * or more of those clients is opened for write.
 *
 * Note that this type of sync IO takes a different path than a file
 * opened with O_SYNC/D_SYNC (writes hit the page cache and are
 * immediately flushed on page boundaries).  It is very similar to
 * O_DIRECT (writes bypass the page cache) excep that O_DIRECT writes
 * are not copied (user page must remain stable) and O_DIRECT writes
 * have alignment restrictions (on the buffer and file offset).
 */
#define CEPH_IOC_SYNCIO …

#endif