diff options
| -rw-r--r-- | fs/ceph/ioctl.h | 55 |
1 files changed, 54 insertions, 1 deletions
diff --git a/fs/ceph/ioctl.h b/fs/ceph/ioctl.h index 0c5167e43180..be4a60487333 100644 --- a/fs/ceph/ioctl.h +++ b/fs/ceph/ioctl.h @@ -6,7 +6,31 @@ #define CEPH_IOCTL_MAGIC 0x97 -/* just use u64 to align sanely on all archs */ +/* + * 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 { __u64 stripe_unit, stripe_count, object_size; __u64 data_pool; @@ -21,6 +45,8 @@ struct ceph_ioctl_layout { struct ceph_ioctl_layout) /* + * 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. */ @@ -39,7 +65,34 @@ struct ceph_ioctl_dataloc { #define CEPH_IOC_GET_DATALOC _IOWR(CEPH_IOCTL_MAGIC, 3, \ struct ceph_ioctl_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 _IO(CEPH_IOCTL_MAGIC, 4) + +/* + * 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 _IO(CEPH_IOCTL_MAGIC, 5) #endif |