exofs: Multi-device mirror support
This patch changes on-disk format, it is accompanied with a parallel
patch to mkfs.exofs that enables multi-device capabilities.
After this patch, old exofs will refuse to mount a new formatted FS and
new exofs will refuse an old format. This is done by moving the magic
field offset inside the FSCB. A new FSCB *version* field was added. In
the future, exofs will refuse to mount unmatched FSCB version. To
up-grade or down-grade an exofs one must use mkfs.exofs --upgrade option
before mounting.
Introduced, a new object that contains a *device-table*. This object
contains the default *data-map* and a linear array of devices
information, which identifies the devices used in the filesystem. This
object is only written to offline by mkfs.exofs. This is why it is kept
separate from the FSCB, since the later is written to while mounted.
Same partition number, same object number is used on all devices only
the device varies.
* define the new format, then load the device table on mount time make
sure every thing is supported.
* Change I/O engine to now support Mirror IO, .i.e write same data
to multiple devices, read from a random device to spread the
read-load from multiple clients (TODO: stripe read)
Implementation notes:
A few points introduced in previous patch should be mentioned here:
* Special care was made so absolutlly all operation that have any chance
of failing are done before any osd-request is executed. This is to
minimize the need for a data consistency recovery, to only real IO
errors.
* Each IO state has a kref. It starts at 1, any osd-request executed
will increment the kref, finally when all are executed the first ref
is dropped. At IO-done, each request completion decrements the kref,
the last one to return executes the internal _last_io() routine.
_last_io() will call the registered io_state_done. On sync mode a
caller does not supply a done method, indicating a synchronous
request, the caller is put to sleep and a special io_state_done is
registered that will awaken the caller. Though also in sync mode all
operations are executed in parallel.
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index 2e08859..c35fd46 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -37,6 +37,11 @@
#include <linux/time.h>
#include "common.h"
+/* FIXME: Remove once pnfs hits mainline
+ * #include <linux/exportfs/pnfs_osd_xdr.h>
+ */
+#include "pnfs.h"
+
#define EXOFS_ERR(fmt, a...) printk(KERN_ERR "exofs: " fmt, ##a)
#ifdef CONFIG_EXOFS_DEBUG
@@ -54,7 +59,6 @@
* our extension to the in-memory superblock
*/
struct exofs_sb_info {
- struct osd_dev *s_dev; /* returned by get_osd_dev */
struct exofs_fscb s_fscb; /* Written often, pre-allocate*/
osd_id s_pid; /* partition ID of file system*/
int s_timeout; /* timeout for OSD operations */
@@ -63,7 +67,11 @@
spinlock_t s_next_gen_lock; /* spinlock for gen # update */
u32 s_next_generation; /* next gen # to use */
atomic_t s_curr_pending; /* number of pending commands */
- uint8_t s_cred[OSD_CAP_LEN]; /* all-powerful credential */
+ uint8_t s_cred[OSD_CAP_LEN]; /* credential for the fscb */
+
+ struct pnfs_osd_data_map data_map; /* Default raid to use */
+ unsigned s_numdevs; /* Num of devices in array */
+ struct osd_dev *s_ods[1]; /* Variable length, minimum 1 */
};
/*