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a9701a3047
We can only accept BARRIER requests if all slaves handle
barriers, and that can, of course, change with time....
So we keep track of whether the whole array seems safe for barriers,
and also whether each individual rdev handles barriers.
We initially assumes barriers are OK.
When writing the superblock we try a barrier, and if that fails, we flag
things for no-barriers. This will usually clear the flags fairly quickly.
If writing the superblock finds that BIO_RW_BARRIER is -ENOTSUPP, we need to
resubmit, so introduce function "md_super_wait" which waits for requests to
finish, and retries ENOTSUPP requests without the barrier flag.
When writing the real raid1, write requests which were BIO_RW_BARRIER but
which aresn't supported need to be retried. So raid1d is enhanced to do this,
and when any bio write completes (i.e. no retry needed) we remove it from the
r1bio, so that devices needing retry are easy to find.
We should hardly ever get -ENOTSUPP errors when writing data to the raid.
It should only happen if:
1/ the device used to support BARRIER, but now doesn't. Few devices
change like this, though raid1 can!
or
2/ the array has no persistent superblock, so there was no opportunity to
pre-test for barriers when writing the superblock.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
100 lines
3.3 KiB
C
100 lines
3.3 KiB
C
/*
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md.h : Multiple Devices driver for Linux
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Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
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Copyright (C) 1994-96 Marc ZYNGIER
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<zyngier@ufr-info-p7.ibp.fr> or
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<maz@gloups.fdn.fr>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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You should have received a copy of the GNU General Public License
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(for example /usr/src/linux/COPYING); if not, write to the Free
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Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _MD_H
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#define _MD_H
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#include <linux/blkdev.h>
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#include <asm/semaphore.h>
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#include <linux/major.h>
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#include <linux/ioctl.h>
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#include <linux/types.h>
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <linux/hdreg.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/smp_lock.h>
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#include <linux/delay.h>
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#include <net/checksum.h>
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#include <linux/random.h>
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#include <linux/kernel_stat.h>
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#include <asm/io.h>
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#include <linux/completion.h>
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#include <linux/mempool.h>
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#include <linux/list.h>
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#include <linux/reboot.h>
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#include <linux/vmalloc.h>
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#include <linux/blkpg.h>
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#include <linux/bio.h>
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/*
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* 'md_p.h' holds the 'physical' layout of RAID devices
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* 'md_u.h' holds the user <=> kernel API
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*
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* 'md_k.h' holds kernel internal definitions
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*/
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#include <linux/raid/md_p.h>
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#include <linux/raid/md_u.h>
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#include <linux/raid/md_k.h>
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/*
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* Different major versions are not compatible.
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* Different minor versions are only downward compatible.
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* Different patchlevel versions are downward and upward compatible.
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*/
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#define MD_MAJOR_VERSION 0
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#define MD_MINOR_VERSION 90
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/*
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* MD_PATCHLEVEL_VERSION indicates kernel functionality.
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* >=1 means different superblock formats are selectable using SET_ARRAY_INFO
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* and major_version/minor_version accordingly
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* >=2 means that Internal bitmaps are supported by setting MD_SB_BITMAP_PRESENT
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* in the super status byte
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* >=3 means that bitmap superblock version 4 is supported, which uses
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* little-ending representation rather than host-endian
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*/
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#define MD_PATCHLEVEL_VERSION 3
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extern int register_md_personality (int p_num, mdk_personality_t *p);
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extern int unregister_md_personality (int p_num);
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extern mdk_thread_t * md_register_thread (void (*run) (mddev_t *mddev),
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mddev_t *mddev, const char *name);
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extern void md_unregister_thread (mdk_thread_t *thread);
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extern void md_wakeup_thread(mdk_thread_t *thread);
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extern void md_check_recovery(mddev_t *mddev);
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extern void md_write_start(mddev_t *mddev, struct bio *bi);
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extern void md_write_end(mddev_t *mddev);
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extern void md_handle_safemode(mddev_t *mddev);
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extern void md_done_sync(mddev_t *mddev, int blocks, int ok);
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extern void md_error (mddev_t *mddev, mdk_rdev_t *rdev);
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extern void md_unplug_mddev(mddev_t *mddev);
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extern void md_print_devices (void);
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extern void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
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sector_t sector, int size, struct page *page);
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extern void md_super_wait(mddev_t *mddev);
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extern int sync_page_io(struct block_device *bdev, sector_t sector, int size,
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struct page *page, int rw);
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#define MD_BUG(x...) { printk("md: bug in file %s, line %d\n", __FILE__, __LINE__); md_print_devices(); }
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#endif
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