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linux-2.6-dm-mpath-fix-io-errors-on-new-path.patch
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File linux-2.6-dm-mpath-fix-io-errors-on-new-path.patch of Package kernel
Date: Mon, 2 Oct 2006 22:17:32 +0100 From: Alasdair G Kergon <agk@redhat.com> Subject: [RHEL5 PATCH] dm mpath: fix adding new path while I/O is pending https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=169302 If you lose all the paths to a dm multipath device you can set queue_if_no_path so that I/O will get queued. If one of your paths comes back, userspace will re-enabled it and the queued I/O will be released. In the current implementation if paths need to be reconfigured while I/O is queued like this any pending I/O must be cleared (with EIO) first: the application receives I/O errors. This patch from NEC allows the multipath tools to set DM_NOFLUSH_FLAG during a suspend operation to request that I/O be queued during such a path reconfiguration. Targets such as multipath then transfer ('push back') their queue of waiting I/O onto the existing queue held in the device-mapper core during a 'suspend' operation. I shall be submitting this upstream via -mm shortly. Index: linux-2.6.18.noarch/drivers/md/dm.c =================================================================== --- linux-2.6.18.noarch.orig/drivers/md/dm.c 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/drivers/md/dm.c 2006-10-02 21:23:51.000000000 +0100 @@ -68,10 +68,12 @@ union map_info *dm_get_mapinfo(struct bi #define DMF_FROZEN 2 #define DMF_FREEING 3 #define DMF_DELETING 4 +#define DMF_NOFLUSH_SUSPENDING 5 struct mapped_device { struct rw_semaphore io_lock; struct semaphore suspend_lock; + spinlock_t pushback_lock; rwlock_t map_lock; atomic_t holders; atomic_t open_count; @@ -90,6 +92,7 @@ struct mapped_device { atomic_t pending; wait_queue_head_t wait; struct bio_list deferred; + struct bio_list pushback; /* * The current mapping. @@ -444,23 +447,50 @@ int dm_set_geometry(struct mapped_device * you this clearly demarcated crap. *---------------------------------------------------------------*/ +static int __noflush_suspending(struct mapped_device *md) +{ + return test_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); +} + /* * Decrements the number of outstanding ios that a bio has been * cloned into, completing the original io if necc. */ static void dec_pending(struct dm_io *io, int error) { - if (error) + unsigned long flags; + + /* Push-back supersedes any I/O errors */ + if (error && !(io->error > 0 && __noflush_suspending(io->md))) io->error = error; if (atomic_dec_and_test(&io->io_count)) { + if (io->error == DM_ENDIO_REQUEUE) { + /* + * Target requested pushing back the I/O. + * This must be handled before the sleeper on + * suspend queue merges the pushback list. + */ + spin_lock_irqsave(&io->md->pushback_lock, flags); + if (__noflush_suspending(io->md)) + bio_list_add(&io->md->pushback, io->bio); + else + /* noflush suspend was interrupted. */ + io->error = -EIO; + spin_unlock_irqrestore(&io->md->pushback_lock, flags); + } + if (end_io_acct(io)) /* nudge anyone waiting on suspend queue */ wake_up(&io->md->wait); - blk_add_trace_bio(io->md->queue, io->bio, BLK_TA_COMPLETE); + if (io->error != DM_ENDIO_REQUEUE) { + blk_add_trace_bio(io->md->queue, io->bio, + BLK_TA_COMPLETE); + + bio_endio(io->bio, io->bio->bi_size, io->error); + } - bio_endio(io->bio, io->bio->bi_size, io->error); free_io(io->md, io); } } @@ -480,12 +510,19 @@ static int clone_endio(struct bio *bio, if (endio) { r = endio(tio->ti, bio, error, &tio->info); - if (r < 0) + if (r < 0 || r == DM_ENDIO_REQUEUE) + /* + * error and requeue request are handled + * in dec_pending(). + */ error = r; - - else if (r > 0) - /* the target wants another shot at the io */ + else if (r == DM_ENDIO_INCOMPLETE) + /* The target will handle the io */ return 1; + else if (r) { + DMWARN("unimplemented target endio return value: %d", r); + BUG(); + } } dec_pending(tio->io, error); @@ -543,7 +580,7 @@ static void __map_bio(struct dm_target * atomic_inc(&tio->io->io_count); sector = clone->bi_sector; r = ti->type->map(ti, clone, &tio->info); - if (r > 0) { + if (r == DM_MAPIO_REMAPPED) { /* the bio has been remapped so dispatch it */ blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone, @@ -551,10 +588,8 @@ static void __map_bio(struct dm_target * clone->bi_sector); generic_make_request(clone); - } - - else if (r < 0) { - /* error the io and bail out */ + } else if (r < 0 || r == DM_MAPIO_REQUEUE) { + /* error the io and bail out, or requeue it if needed */ md = tio->io->md; dec_pending(tio->io, r); /* @@ -563,6 +598,9 @@ static void __map_bio(struct dm_target * clone->bi_private = md->bs; bio_put(clone); free_tio(md, tio); + } else if (r) { + DMWARN("unimplemented target map return value: %d", r); + BUG(); } } @@ -948,6 +986,7 @@ static struct mapped_device *alloc_dev(i memset(md, 0, sizeof(*md)); init_rwsem(&md->io_lock); init_MUTEX(&md->suspend_lock); + spin_lock_init(&md->pushback_lock); rwlock_init(&md->map_lock); atomic_set(&md->holders, 1); atomic_set(&md->open_count, 0); @@ -1275,12 +1314,15 @@ static void unlock_fs(struct mapped_devi * dm_bind_table, dm_suspend must be called to flush any in * flight bios and ensure that any further io gets deferred. */ -int dm_suspend(struct mapped_device *md, int do_lockfs) +int dm_suspend(struct mapped_device *md, unsigned suspend_flags) { struct dm_table *map = NULL; + unsigned long flags; DECLARE_WAITQUEUE(wait, current); struct bio *def; int r = -EINVAL; + int do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG ? 1 : 0; + int noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG ? 1 : 0; down(&md->suspend_lock); @@ -1289,6 +1331,13 @@ int dm_suspend(struct mapped_device *md, map = dm_get_table(md); + /* + * DMF_NOFLUSH_SUSPENDING must be set before presuspend. + * This flag is cleared before dm_suspend returns. + */ + if (noflush) + set_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); + /* This does not get reverted if there's an error later. */ dm_table_presuspend_targets(map); @@ -1296,11 +1345,14 @@ int dm_suspend(struct mapped_device *md, if (!md->suspended_bdev) { DMWARN("bdget failed in dm_suspend"); r = -ENOMEM; - goto out; + goto flush_and_out; } - /* Flush I/O to the device. */ - if (do_lockfs) { + /* + * Flush I/O to the device. + * noflush supersedes do_lockfs, because lock_fs() needs to flush I/Os. + */ + if (do_lockfs && !noflush) { r = lock_fs(md); if (r) goto out; @@ -1336,6 +1388,14 @@ int dm_suspend(struct mapped_device *md, down_write(&md->io_lock); remove_wait_queue(&md->wait, &wait); + if (noflush) { + spin_lock_irqsave(&md->pushback_lock, flags); + clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); + bio_list_merge_head(&md->deferred, &md->pushback); + bio_list_init(&md->pushback); + spin_unlock_irqrestore(&md->pushback_lock, flags); + } + /* were we interrupted ? */ r = -EINTR; if (atomic_read(&md->pending)) { @@ -1344,7 +1404,7 @@ int dm_suspend(struct mapped_device *md, __flush_deferred_io(md, def); up_write(&md->io_lock); unlock_fs(md); - goto out; + goto out; /* pushback list is already flushed, so skip flush */ } up_write(&md->io_lock); @@ -1354,6 +1414,25 @@ int dm_suspend(struct mapped_device *md, r = 0; +flush_and_out: + if (r && noflush) { + /* + * Because there may be already I/Os in the pushback list, + * flush them before return. + */ + down_write(&md->io_lock); + + spin_lock_irqsave(&md->pushback_lock, flags); + clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); + bio_list_merge_head(&md->deferred, &md->pushback); + bio_list_init(&md->pushback); + spin_unlock_irqrestore(&md->pushback_lock, flags); + + def = bio_list_get(&md->deferred); + __flush_deferred_io(md, def); + up_write(&md->io_lock); + } + out: if (r && md->suspended_bdev) { bdput(md->suspended_bdev); @@ -1438,6 +1517,17 @@ int dm_suspended(struct mapped_device *m return test_bit(DMF_SUSPENDED, &md->flags); } +int dm_noflush_suspending(struct dm_target *ti) +{ + struct mapped_device *md = dm_table_get_md(ti->table); + int r = __noflush_suspending(md); + + dm_put(md); + + return r; +} +EXPORT_SYMBOL_GPL(dm_noflush_suspending); + static struct block_device_operations dm_blk_dops = { .open = dm_blk_open, .release = dm_blk_close, Index: linux-2.6.18.noarch/drivers/md/dm-ioctl.c =================================================================== --- linux-2.6.18.noarch.orig/drivers/md/dm-ioctl.c 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/drivers/md/dm-ioctl.c 2006-10-02 21:20:03.000000000 +0100 @@ -760,7 +760,7 @@ out: static int do_suspend(struct dm_ioctl *param) { int r = 0; - int do_lockfs = 1; + unsigned suspend_flags = DM_SUSPEND_LOCKFS_FLAG; struct mapped_device *md; md = find_device(param); @@ -768,10 +768,12 @@ static int do_suspend(struct dm_ioctl *p return -ENXIO; if (param->flags & DM_SKIP_LOCKFS_FLAG) - do_lockfs = 0; + suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG; + if (param->flags & DM_NOFLUSH_FLAG) + suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG; if (!dm_suspended(md)) - r = dm_suspend(md, do_lockfs); + r = dm_suspend(md, suspend_flags); if (!r) r = __dev_status(md, param); @@ -783,7 +785,7 @@ static int do_suspend(struct dm_ioctl *p static int do_resume(struct dm_ioctl *param) { int r = 0; - int do_lockfs = 1; + unsigned suspend_flags = DM_SUSPEND_LOCKFS_FLAG; struct hash_cell *hc; struct mapped_device *md; struct dm_table *new_map; @@ -809,9 +811,11 @@ static int do_resume(struct dm_ioctl *pa if (new_map) { /* Suspend if it isn't already suspended */ if (param->flags & DM_SKIP_LOCKFS_FLAG) - do_lockfs = 0; + suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG; + if (param->flags & DM_NOFLUSH_FLAG) + suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG; if (!dm_suspended(md)) - dm_suspend(md, do_lockfs); + dm_suspend(md, suspend_flags); r = dm_swap_table(md, new_map); if (r) { Index: linux-2.6.18.noarch/include/linux/device-mapper.h =================================================================== --- linux-2.6.18.noarch.orig/include/linux/device-mapper.h 2006-10-02 21:20:01.000000000 +0100 +++ linux-2.6.18.noarch/include/linux/device-mapper.h 2006-10-02 21:20:03.000000000 +0100 @@ -39,7 +39,8 @@ typedef void (*dm_dtr_fn) (struct dm_tar * The map function must return: * < 0: error * = 0: The target will handle the io by resubmitting it later - * > 0: simple remap complete + * = 1: simple remap complete + * = 2: The target wants to push back the io */ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio, union map_info *map_context); @@ -50,6 +51,7 @@ typedef int (*dm_map_fn) (struct dm_targ * 0 : ended successfully * 1 : for some reason the io has still not completed (eg, * multipath target might want to requeue a failed io). + * 2 : The target wants to push back the io */ typedef int (*dm_endio_fn) (struct dm_target *ti, struct bio *bio, int error, @@ -174,7 +176,7 @@ void *dm_get_mdptr(struct mapped_device /* * A device can still be used while suspended, but I/O is deferred. */ -int dm_suspend(struct mapped_device *md, int with_lockfs); +int dm_suspend(struct mapped_device *md, unsigned suspend_flags); int dm_resume(struct mapped_device *md); /* @@ -189,6 +191,7 @@ int dm_wait_event(struct mapped_device * const char *dm_device_name(struct mapped_device *md); struct gendisk *dm_disk(struct mapped_device *md); int dm_suspended(struct mapped_device *md); +int dm_noflush_suspending(struct dm_target *ti); /* * Geometry functions. Index: linux-2.6.18.noarch/drivers/md/dm.h =================================================================== --- linux-2.6.18.noarch.orig/drivers/md/dm.h 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/drivers/md/dm.h 2006-10-02 21:20:03.000000000 +0100 @@ -33,6 +33,25 @@ #define SECTOR_SHIFT 9 /* + * Definitions of return values from target end_io function. + */ +#define DM_ENDIO_INCOMPLETE 1 +#define DM_ENDIO_REQUEUE 2 + +/* + * Definitions of return values from target map function. + */ +#define DM_MAPIO_SUBMITTED 0 +#define DM_MAPIO_REMAPPED 1 +#define DM_MAPIO_REQUEUE DM_ENDIO_REQUEUE + +/* + * Suspend feature flags + */ +#define DM_SUSPEND_LOCKFS_FLAG (1 << 0) +#define DM_SUSPEND_NOFLUSH_FLAG (1 << 1) + +/* * List of devices that a metadevice uses and should open/close. */ struct dm_dev { Index: linux-2.6.18.noarch/drivers/md/dm-bio-list.h =================================================================== --- linux-2.6.18.noarch.orig/drivers/md/dm-bio-list.h 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/drivers/md/dm-bio-list.h 2006-10-02 21:20:03.000000000 +0100 @@ -44,6 +44,20 @@ static inline void bio_list_merge(struct bl->tail = bl2->tail; } +static inline void bio_list_merge_head(struct bio_list *bl, + struct bio_list *bl2) +{ + if (!bl2->head) + return; + + if (bl->head) + bl2->tail->bi_next = bl->head; + else + bl->tail = bl2->tail; + + bl->head = bl2->head; +} + static inline struct bio *bio_list_pop(struct bio_list *bl) { struct bio *bio = bl->head; Index: linux-2.6.18.noarch/include/linux/dm-ioctl.h =================================================================== --- linux-2.6.18.noarch.orig/include/linux/dm-ioctl.h 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/include/linux/dm-ioctl.h 2006-10-02 21:20:03.000000000 +0100 @@ -285,7 +285,7 @@ typedef char ioctl_struct[308]; #define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl) #define DM_VERSION_MAJOR 4 -#define DM_VERSION_MINOR 9 +#define DM_VERSION_MINOR 11 #define DM_VERSION_PATCHLEVEL 0 #define DM_VERSION_EXTRA "-ioctl (2006-09-14)" @@ -323,4 +323,9 @@ typedef char ioctl_struct[308]; */ #define DM_SKIP_LOCKFS_FLAG (1 << 10) /* In */ +/* + * Set this to suspend without flushing queued ios. + */ +#define DM_NOFLUSH_FLAG (1 << 11) /* In */ + #endif /* _LINUX_DM_IOCTL_H */ Index: linux-2.6.18.noarch/drivers/md/dm-mpath.c =================================================================== --- linux-2.6.18.noarch.orig/drivers/md/dm-mpath.c 2006-10-02 21:18:07.000000000 +0100 +++ linux-2.6.18.noarch/drivers/md/dm-mpath.c 2006-10-02 21:27:55.000000000 +0100 @@ -282,10 +282,13 @@ failed: m->current_pg = NULL; } +#define __PUSHBACK(m) (!(m)->queue_if_no_path && (m)->saved_queue_if_no_path && \ + dm_noflush_suspending((m)->ti)) + static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio, unsigned was_queued) { - int r = 1; + int r = DM_MAPIO_REMAPPED; unsigned long flags; struct pgpath *pgpath; @@ -310,10 +313,13 @@ static int map_io(struct multipath *m, s !m->queue_io) queue_work(kmultipathd, &m->process_queued_ios); pgpath = NULL; - r = 0; - } else if (!pgpath) + r = DM_MAPIO_SUBMITTED; + } else if (!pgpath) { r = -EIO; /* Failed */ - else + + if (__PUSHBACK(m)) + r = DM_MAPIO_REQUEUE; + } else bio->bi_bdev = pgpath->path.dev->bdev; mpio->pgpath = pgpath; @@ -372,8 +378,16 @@ static void dispatch_queued_ios(struct m r = map_io(m, bio, mpio, 1); if (r < 0) bio_endio(bio, bio->bi_size, r); - else if (r == 1) + else if (r == DM_MAPIO_REMAPPED) generic_make_request(bio); + else if (r == DM_MAPIO_REQUEUE) + /* + * end_io handles the requeue request by + * returning the bio with error status. + * We don't return the r value to end_io, + * since it is probably not needed. + */ + bio_endio(bio, bio->bi_size, -EIO); bio = next; } @@ -781,7 +795,7 @@ static int multipath_map(struct dm_targe map_context->ptr = mpio; bio->bi_rw |= (1 << BIO_RW_FAILFAST); r = map_io(m, bio, mpio, 0); - if (r < 0) + if (r < 0 || r == DM_MAPIO_REQUEUE) mempool_free(mpio, m->mpio_pool); return r; @@ -1005,7 +1019,10 @@ static int do_end_io(struct multipath *m spin_lock_irqsave(&m->lock, flags); if (!m->nr_valid_paths) { - if (!m->queue_if_no_path) { + if (__PUSHBACK(m)) { + spin_unlock_irqrestore(&m->lock, flags); + return DM_ENDIO_REQUEUE; + } else if (!m->queue_if_no_path) { spin_unlock_irqrestore(&m->lock, flags); return -EIO; } else { @@ -1040,7 +1057,7 @@ static int do_end_io(struct multipath *m queue_work(kmultipathd, &m->process_queued_ios); spin_unlock_irqrestore(&m->lock, flags); - return 1; /* io not complete */ + return DM_ENDIO_INCOMPLETE; /* io not complete */ } static int multipath_end_io(struct dm_target *ti, struct bio *bio, @@ -1058,7 +1075,7 @@ static int multipath_end_io(struct dm_ta if (ps->type->end_io) ps->type->end_io(ps, &pgpath->path); } - if (r <= 0) + if (r != DM_ENDIO_INCOMPLETE) mempool_free(mpio, m->mpio_pool); return r;
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